GSB INTERNATIONAL e.V.

Qualitätsgemeinschaft

für die Stückbeschichtung

von Bauteilen

Vereinsregister VR 10645

Düsseldorf

ID-NR. DE 152599832

Deutsche Bank Düsseldorf

BLZ 300 700 10

Konto Nr. 46 77 043

Swift Code: DEUTDEDD

IBAN: DE96300700100467704300

GSB INTERNATIONAL Am Bonneshof 5, D-40474 Düsseldorf Consultation Number 0032-5 Surface treatment (except passivation of tin-plated steel (ETP)) for applications in various industry sectors namely architectural, automotive, metal manufacturing and finishing, and general engineering (unrelated to Functional chrome plating or Functional chrome plating with decorative character) Dear Ladies and Gentlemen,

Please find attached the documentation “Chromium-free Surface Pretreatment for Aluminium, State Of The Art, GSB International, 2012” which is mentioned in 0032-5 “Analysis of Alternatives”.

The documentation describes the development and state of the art of surface pretreatment processes in the field of piecework coating of aluminium in architecture. Today there are GSB approved and sufficient processes available that are of equivalent quality and competitive to chromium-VI-containing processes. This processes passed the GSB test and approval regime with the highest standards in the market as mentioned in 0032-5 “Analysis of Alternatives”.

Today for steel and galvanized steel there are no GSB-approved chromium-free process as pretreatment before coating available. Some projects are running to develop chromium-free processes which are comparable to chromium-VI-containing processes.

If you have any question please do not hesitate to contact me.

Kind regards

Werner Mader

Attachment

Chromium-free Surface Pretreatment for Aluminium, State Of The Art, GSB International, 2012

GSB INTERNATIONAL Am Bonneshof 5 D-40474 Düsseldorf Telefon +49 (0) 211/4796 - 451 Telefax +49 (0) 211/4796 - 410 www.gsb-international.de info@gsb-international.de Geschäftsführung: Werner Mader 07.10.2015

Chromium-free

Surface Pretreatment For Aluminium State Of The Art

1

Chromium-free surface pretreatment of aluminium Documentation of the prior art

Preface

In the early 1990s, the State of Berlin issued the ban on the use of aluminium as a building material, against which the General Association of the Aluminium Industry (GDA) filed a successful opposition. However, this was associated with the requirement that chromium-free processes must be used in future for the surface pretreatment.

GSB International has faced this challenge for more than 15 years, and has worked extensively on the introduction and approval of chromium-free pretreatment processes. In close co-operation with pretreatment chemical manufacturers and coating companies, approval procedures for alternative systems were developed and then implemented in the quality guidelines. Only in 1994 was approval granted for a chromium-free pretreatment process to ensure that member companies could continue to serve their markets with alternative processes with a high quality level. Therefore, since that time, proven chromium-free pretreatment processes have become available that behave in a stable way under production conditions, have shown high corrosion resistance in long-term weathering tests and are commercially competitive.

Since its foundation over 30 years ago, GSB International has pursued a consistent strategy of developing quality-assured products, with due consideration of environmentally friendly technologies and procedures. The selection of the processes and operating sequences remains exclusively within the corporate responsibility of each individual member company. As in the past, GSB International does not specify any requirements in the quality standards that exceed the regulatory framework.

At the end of 2010, the ECHA placed chromium (VI) oxide and other chromium (VI)-containing compounds on the list of substances of very high concern (SVHC list) because they are carcinogenic and mutagenic. This raises the very important question of the future of chromating as a pretreatment process for aluminium in construction. Nevertheless, this problem has been known since the 1990s in the industrial sectors in question.

Our organisation therefore acted in a timely manner to find alternative chromium-free pretreatment processes.

The present documentation describes the development and state of the art of surface pretreatment processes in the field of piecework coating of aluminium in architecture. It also provides an insight into other markets and processes, such as coil coating, which are affected by similar legal regulations.

Düsseldorf, July 2012

Hans-Jürgen Alfort

Chairman of the Board

2

Contents

Chromium-free surface pretreatment of aluminium 1 1 Introduction 5 1.1 Current situation 5 1.2 Health endangerment 6

2 Statutory provisions 7 2.1 Architecture and construction 7 2.2 Other markets 8

3 GSB International 9 3.1 General information 9 3.2 State of the art at the time of the foundation of GSB International in 1976 9 3.3 Certification procedures of GSB International 9 3.4 Expanded certification criteria 11 3.5 Extension of natural weathering 12 3.6 Certified systems 14

4 The current development status of chromium-free processes from the perspective of the chemical manufacturers 16

4.1 Alufinish GmbH & Co. KG, D-Andernach 17 4.2 Chemetall GmbH, D-Frankfurt am Main 21 4.3 Henkel KGaA, D-Düsseldorf 26 4.4 MacDermid GmbH, D-Forst 28 4.5 Nabu-Oberflächentechnik GmbH, D-Stulln-Nabburg 29 4.6 SurTec International GmbH, D-Bensheim 33

5 The current development status of chromium-free processes from the perspective of the coaters 34

5.1 General information 34 5.2 Alulux Beckhoff GmbH & Co., D-Verl 35 5.3 Alumil-Milonas Aluminium Industry S.A., GR-Kilkis 36 5.4 heroal – Aluminiumgesellschaft Hövelhof mbH & Co. KG, D-Verl 40 5.5 LOV-Limbacher Oberflächenveredelung GmbH, D-Limbach-Oberfrohna 41 5.6 TK-Oberfläche GmbH, D-Bielefeld

and PBS Schreiner GmbH & Co. KG, D-Grebenau 46 5.7 Warema Renkhoff SE, D-Marktheidenfeld 52

3

6 Chromium-free pretreatment for coil coating 55 6.1 Hydro Aluminium Rolled Products GmbH, D-Grevenbroich and

Novelis Deutschland GmbH, D-Göttingen 55

7 Preanodisation 65 8 Summary 67

The contributions in Chapters 4, 5 and 6 represent the opinions and experience of the company. The content is solely the responsibility of the company.

4

5

1 Introduction

1.1 Current situation

On 01.06.2007, the REACH regulation came into force to replace the existing chemicals legislation in

the European Union (EU).

The REACH regulation has established a certification procedure for substances of very high concern.

As of 30.06.2011, there are 53 substances included on the candidate list (SVHC list) for certification.

The objective of the EU Commission is to expand the list to 136 substances by the end of 2013.

Publication in the "candidate list" does not result in mandatory certification but rather far-reaching

information requirements in the supply chain. REACH requires companies to inform their business

customers if their products contain more than 0.1 per cent of a chemical identified in the list.

At the end of 2010, the European Chemicals Agency (ECHA) added chromium (VI) oxide and other

chromium (VI) compounds to the candidate list for substances of very high concern (SVHC list).

The list of substances subject to mandatory certification now contains 6 substances, for which the

companies concerned must submit certification applications by 2013. The inclusion process is

currently under way for a further 13 substances. This also applies to chromium (VI) oxide, chromic

acid and other chromium (VI) compounds. After inclusion in Annex XIV of the REACH regulation, a

certification must be applied for prior to each use. The EU Commission makes the decision regarding

the certification.

The possible consequences are:

chromate-containing surface pretreatment processes may continue to be used. The required

registration of the chemicals with the ECHA is very expensive, which may lead to an increase

in the process costs.

relocation of production to non-REACH countries. The importation of chromate-containing

products without registration with the ECHA is prohibited. Here also, the required registration

can lead to price increases.

The use of chromate-containing surface pretreatment processes is prohibited without

exception.

According to current knowledge, a final decision by the European Commission is anticipated within the

next 5 years.

6

1.2 Health endangerment

Toxicological significance is ascribed to chromium (VI) compounds, which have the potential to cause

cancer. Their classification as compounds with carcinogenic and mutagenic potential has been known

for many years.

Metallic chromium and trivalent chromium compounds, such as the chromium (III)-phosphate that

makes up the green chromating layer, are not irritant, mutagenic or carcinogenic. However, the

production of process chemicals always starts from chromium (VI) compounds. Thus, the handling of

hazardous chemicals is assumed here, and particular caution is required.

Chromium (III) compounds are not included in the SVHC list, and therefore can still be used without

restriction.

7

2 Statutory provisions

2.1 Architecture and construction

The relevant national building codes and rules do not currently prohibit the use of chromium-

containing surface pretreatments.

However, individual cities and districts have switched over in their tenders to the mandatory

prescription of chromium-free pretreatments.

As early as 1990, the Building/Living Senate in Berlin, in the 40th Official Journal, prohibited the use of

building materials posing a high health and environmental hazard, and thus banned the use of window

and door profiles made of aluminium. At the meeting of 19.02.1998 (document 13/2002) in the context

of the lifting of the restriction on the use of aluminium in the regulatory area of public sector and

publicly funded construction, the Berlin Senate declared that aluminium is only allowed if

a pledge of commitment by the manufacturer for product-related recycling and

a declaration by the contractor on the chromium-free primer for coloured aluminium

components exist.

There is therefore no differentiation between chromium (VI) and chromium (III) compounds, but the

use of chromium is generally prohibited.

The decision of the Berlin Senate had a nationwide impact and so other cities, such as Munich, also

introduced the same or similar regulations.

The certification systems for sustainable construction (LEED, DGNB, etc.) also provide, in their

evaluation rules for building, positive points for the use of chromium-free surface pretreatment

processes for aluminium. For this reason, architects are increasingly inviting tenders for chromium-free

surface pretreatments.

Other European countries, like Spain, France and Greece, already have a market share of more than

60% made up of chromium-free pretreatments. In 2011, China enacted a ban on the use of chromium

(VI)-containing pretreatments in architecture.

8

2.2 Other markets

Other markets have already gone one step further here. By virtue of the Directive on End-of Life

Vehicles (2000/53/EC, 1 July 2003/1 July 2007), the use of Cr (VI)-containing compounds has long

been prohibited. Some car manufacturers have generally rejected chromium-containing compounds in

pretreatments and in the processes for surface pretreatment of aluminium.

The same applies to electrical appliances. Here the guidelines

ROHS (EU Directive 2002/95/EC on Restriction Of The Use Of Certain Hazardous

Substances In Electrical And Electronic Equipment, 1 July 2006) and

WEEE (EU Directive 2002/96/EC on Waste Electrical And Electronic Equipment, 1 July 2006)

should be highlighted.

Even in the aerospace industry, chromic acid anodisation is being replaced by tartaric acid

anodisation. New projects are generally only tendered for with tartaric acid anodisation.

9

3 GSB International

3.1 General information

These developments prompted GSB International to test chromium-free pretreatment processes in

observance of the high and proven quality standards and to incorporate them into the quality

standards as a GSB International-compatible pretreatment.

3.2 State of the art at the time of the foundation of GSB International in 1976

For more than 50 years, in the pretreatment of aluminium, chromating has performed the tasks of

improving adhesion for subsequent coating and serving as a barrier layer against substances diffusing

through any organic layer, such as water vapour or corrosive atmospheric gases. This applies to

coating with liquid and powder coats.

We primarily differentiate between yellow and green chromating. Whereas the yellow chromatic layer,

which primarily consists of chromium oxide (Cr203), still contains Cr(VI) ions, no chromium (VI) ions

can be detected any more in the green chromating layer, which primarily consists of chromium

phosphate (Cr(III)PO4). Chromium-containing conversion layers created both in the dipping and

spraying processes deliver comparably good results in relation to adhesion promotion and corrosion

inhibition. In all chromating processes, thorough rinsing to remove the adhering treatment solution is

necessary. This requires the preparation of chromate-containing rinse water to prevent chromate from

entering the waste water.

3.3 Certification procedures of GSB International

In addition to inhibiting corrosion and improving paint adhesion, for all certified and used paint

systems, the equipment suitability, processing properties and process stability of the pretreatment

process are particularly important.

This led the Technical Committee (TC) of GSB International, in developing a certification process for

alternative, chromium-free pretreatment chemicals, to propose a multi-stage sequence:

10

- Stage 1:

Application of the chemical suppliers to GSB International for certification of the relevant

pretreatment system.

Presentation of the system and discussion with the Technical Committee (TC)

For this purpose, the following documents must be prepared:

Presentation of individual results based on GSB QR AL 631

Submission of tested sample sheets

Submission of current product data sheets and material safety data sheets

Names of reference objects, if applicable

Evidence of product suitability for dipping plants and/or spraying equipment

Evidence of product suitability for powder and/or liquid coats

Plant experience

- Stage 2:

The pretreatment, coating and testing according to GSB QR AL 631 of the sample plates is

performed in a test institute to be named by the TC.

As a reference, a commercial yellow chromating has been used so far. A chromium-free "master

process" is being tested. The samples pretreated with the reference material are coated and

tested the same way.

As a reference material, a reference powder coat determined by the TC is used. The tests and

requirements are summarised in section 8.2.6 of GSB QR AL 631.

- Stage 3:

If the results of stage 2 are positive, a plant test is performed at a coating company that is a

member of GSB International.

Stage 3 must be performed in a production plant; here, the material must be pretreated with a

surface area of at least 500 m². 25 m² from the middle and end of the pretreatment lot respectively

must be coated and exposed as an object of natural weathering.

The consent of the TC for the coating company and the object is required.

The documentation of the plant test is created by an observer appointed by the TC.

11

After a positive evaluation of the results of field tests in accordance with section 8.2.6 of GSB QR

AL 631, the preliminary certification for the pretreatment system is granted.

Only the findings from the field tests confirm the plant suitability and process stability of the

alternative treatment processes.

- Stage 4:

Sample material from the pilot test (stage 3) is weathered for three years in a near-shore industrial

climate (preferably in Hoek van Holland in the Netherlands). Once the natural weathering results

have been obtained, if the progression is positive, the final certification may be granted and

authenticated for the pretreatment system.

- Extension test

The certified alternative pretreatment chemicals, like the coating materials, are subject to an

annual extension test. The test samples required for the extension test, in the form of ready-

coated profiles or sheets, are removed by the tester from a coater who is routinely using the

pretreatment chemical to be tested. In the event of positive test results, the certification is

extended by one year.

3.4 Expanded certification criteria

For alternative pretreatment processes, increased care in degreasing, pickling and rinsing with

completely desalinated water (DW) prior to the conversion treatment is crucial. The quality of the

product "coated material" is essentially dependent on the pretreatment, the coating material and the

careful application of the coating. Therefore, in the currently valid quality guidelines, expanded

certification criteria have been included.

Thus, in 2007, GSB International introduced the status of "premium coater". The most important

quality criterion for the premium coater is the precise definition of the pretreatment process with

product testing.

12

Here, for the first time in a quality community, the entire pretreatment process is documented, stored

and monitored by means of corrosion tests on coated products. Process changes must always be

communicated. Another aspect is the increased documentation of self-monitoring for the premium

coater.

With the premium segment for the coater and the coating material, there is increased security for the

life expectancy of constructed façade sections. For the first time, the detailed definition and monitoring

ensures additional security, which is not the case with national and international standards.

3.5 Extension of natural weathering

Since the beginning of the natural weathering tests in Hoek van Holland, GSB International did not

end the exposure after three years, but extended the test period to ten years. The samples removed

after ten years were documented and handed over to the respective pretreatment manufacturers for

storage.

Examples after ten years of natural weathering in Hoek van Holland, with chromium-free pretreatment

processes:

Image: Alodine 4830 (Henkel), exposure 1999

Image: Alfipas 745 (Alufinish), exposure 1998

13

Image: Alficoat 748 (Alufinish), exposure 2001

Image: Nabutan STI 310 (Nabu), exposure 1998

Image: X4707 (Chemetall), exposure 1999

14

3.6 Certified systems

Alternative pretreatment systems, chromium-free (Rinse and No-Rinse)

Company Internet System

Certification Henkel KGaA www.henkel-

technologies.de Alodine 4830/31

(powder coating area) Stage 4

Alodine 400 Stage 4

NABU-

Oberflächentechnik GmbH

www.nabu-stulln.de Nabutan STI / 310 (powder coating area)

Stage 4

Nabutan 900 Stage 2

Alufinish GmbH &

Co. KG www.alufinish.de Alfipas 745/746 (powder

coating area) Stage 4

Alficoat 748 (powder coating area)

Stage 4

Alfipas 7816 Stage 3

Chemetall GmbH www.chemetall.com Gardobond X 4707 Stage 4

Oxsilan AL 0510 Stage 3

Chemische Werke Kluthe

www.kluthe.com Deccordal Al230A Stage 4

CHEMAL GmbH &

Co. KG www.chemal.com Non-Chrome B.K.-3990 Stage 4

MacDermid GmbH www.macdermid.com Iridite CF (powder

coating area)Stage 4

AD Chemicals B.V. www.adinternational.com Precoat Cr-free (powder

coating area)Stage 3

Surf Chem – Skylodimos

Bros.

SurfPass Ti NOC Powder coating area

Stage 3

15

Alternative pretreatment systems, chromate-free (Rinse and No-Rinse)

Company Internet System

Certification

Henkel KGaA www.henkel-technologies.de

Alodine 5992 Stage 3

SurTec International

GmbH www.surtec.com SurTec ChromitAl

650 TCP(powder coating area)

Stage 3

16

4 The current development status of chromium-free processes from the perspective of the

chemical manufacturers

The following contributions reflect the opinions and experiences of the companies. The

content is solely the responsibility of the chemical manufacturers.

Schematic representation of the different surface pretreatment processes

17

4.1 Alufinish GmbH & Co. KG, D-Andernach

4.1.1 Alfipas 745 - Alfipas 746 (ENVIROX S - process)

This system is a two-component system for the pretreatment of aluminium surfaces, consisting of the

Alfipas 745 (titanium-containing component) and the polymer component Alfipas 746. Both

components are liquid and therefore automatically dosed. Alfipas 745 - Alfipas 746 can both be

applied in dipping as well as spraying processes, and then rinsed, as is usual in chromating

processes. The preparation is performed in fully desalinated water. The layer is about 30 nm thick; the

ideal titanium layer application is 2 - 10 mg Ti/m².

The conversion coating produced is colourless and can be easily made visible by a dye spot test

(quick test). The precise titanium layer application is determined quantitatively by the photometric layer

determination method. In addition, detection with X-ray fluorescence analysis is possible.

Alfipas 745 and 746 received the final GSB International certification already in January 2002. The 10-

year natural weathering in Hoek van Holland (NL) by GSB International was completed successfully in

January 2009.

Alfipas 745 and 746 is currently used in 5 countries - Germany, Belgium, Hungary, Greece and the

Czech Republic - in the fields of architecture, medical equipment, household appliances and

machinery.

Image: Company facade of ALUCOLOR Oberflächenveredlung GmbH & Co. KG, D-Chemnitz

Implementation: March 1998, area 1059 m²

18

4.1.2 Alficoat 748 (ENVIROX NR process)

Alficoat 748 is a 1-component product based on titanium and polymer compounds for the pretreatment

of aluminium surfaces. It is liquid, may be automatically dosed, and can be applied both in dipping and

spraying processes.

Since this is a no-rinse product, a final rinse is not required. The preparation is performed in fully

desalinated water.

The layer is about 30 nm thick; the ideal titanium layer application is 2 - 10 mg Ti/m². Also available as

detection methods are the quick test, photometric determination and X-ray fluorescence analysis. The

10-year natural weathering in Hoek van Holland (NL), according to information from the FEM Institute

in Schwäbisch Gmünd, was successful, and an official letter from GSB International is expected in late

November.

Alficoat 748 is already used in machine engineering and architecture in 16 European and Eastern

European countries, as well as in the Middle East.

Image: Production of 55 m² façade panels for the operations building of Zuck Mechanik GmbH,

D-Ochtendung, execution: May 2001

19

4.1.3 Experiences and special features of Alficoat 748 and Alfipas 745 - Alfipas 746

Chromium-free systems are more sensitive than chromating. Therefore, a good rinsing technique, in

particular prior to the chromium-free pretreatment, is required (dripping water at maximum 30 μS/cm)

in order to reduce the entry of pollutants. In addition to determining the concentration, the

measurement of the pH and conductivity, Alfipas 745 - Alfipas 746 and Alficoat 748 baths are

determined via the V-value. This includes the degree of contamination. Thus it can be easily

determined when a bath should be renewed (similar to chromium (III) determination with chromating).

For turbid baths, a simple filtration process is also available (Envirox cartridge filter system), which can

eliminate harmful precipitates. In continuously operating plants with high throughput, the bath should

constantly be partially renewed to keep the entry of contaminants or degradation products to a

(harmless) level. We also recommend that, for large goods throughput and the use of Alficoat 748,

after-misting of the chromium-free treated surfaces with fully desalinated water (low water quantity) be

performed to remove any product residues from the drip rail. A trouble-free application is possible if

these points and the specified operating parameters are considered.

4.1.4 Alfipas 7816 (ENVIROX SG process)

The ENVIROX SG process is the latest development of our chromium-free pretreatment processes.

Alfipas 7816 is a 1-component product and contains zirconium- and polymer-containing compounds. It

is a sol-gel system that is suitable for the pretreatment of various metal surfaces (aluminium alloys,

steel and galvanised surfaces). It is liquid and can therefore be automatically dosed. The preparation

is in fully desalinated water, and a brief rinse in the same water is also required. It can be applied both

in dipping and spraying processes.

The layer thickness is in the nanometre range.

The conversion coating produced is colourless on aluminium and galvanised surfaces; on steel

surfaces, however, it appears yellowish-brown.

The same may easily be made visible by the dye spot test (quick test). The precise layer application

(expressed in extinction values) is determined quantitatively by the photometric layer determination

method.

20

Stage 2 of the GSB International certification procedure was completed successfully. An official

statement by GSB International will be available shortly.

Alfipas 7816 is currently being used in 9 European and Eastern European countries, as well as in the

Middle East, for the pretreatment of office furniture (steel), and galvanised fences, as well as other

custom coatings of aluminium and steel.

21

4.2 Chemetall GmbH, D-Frankfurt am Main

4.2.1 Chromium-free alternatives for every application

Nearly 40 million tons of aluminium are manufactured worldwide each year. The main customers

include the construction and automotive industries, as well as the mechanical and plant engineering.

Due to its chemical properties, like many other metals, aluminium must be protected by pretreatment

against environmental influences. In addition to corrosion protection, these measures are also used to

ensure better paint adhesion. The chromium-free alternatives described below have proven

themselves over many years of use, and are characterised by particular application-specific strengths:

Gardobond® X 4707 (titanium- / zirconium-containing process)

Gardobond® X 4661 (Self Assembling Molecules (SAM) process)

Permatreat® 1903 (aluminium pretreatment process)

OXSILAN® (silane-based process)

4.2.2 Impeccable façades even after 15 years

Glass, concrete and aluminium now determine the image of modern architecture. Above all, doors,

windows, window sills and entire façade panels are made of flexible lightweight material aluminium.

Because heat, sun and salty or polluted air place extreme demands on corrosion protection, all

products are pretreated and then either powder-coated or painted. Chromium-free Gardobond® X

products have proven themselves in this market for over a decade. Since then, in the building industry

alone, many millions of square metres of aluminium have been coated with Gardobond® X processes!

Qualitative or visual impairments cannot be observed, even over the long term. Façade panels from

the world's leading manufacturer A&MS also show no signs of ageing for years. Today, the second,

more advanced generation is already in use under the name Gardobond® X 4707. This technology,

based on titanium and zirconium, shows excellent results in all of the usual test processes (NSS,

CASS or filiform). Even under the most difficult conditions, such as the ten-year GSB International

"Natural Weathering Test" (Hoek van Holland, Netherlands), aluminium samples prepared with

Gardobond® X 4707 outperformed chromated pendants. In addition to GSB International certification,

Gardobond® X 4707 is certified by Qualicoat and meets the AAMA requirements.

22

4.2.3 Other fully certified alternatives

With the silane-based Oxsilan® AL 0510, Chemetall offers another chromium-free alternative that also

has all the necessary certifications for the construction industry (GSB International, Qualicoat).

Specially developed for the pretreatment of aluminium-containing alloys and other metals, the

environmentally friendly OXSILAN® process has been successfully used for many years in the

household appliance and automotive industries (see below). Both aluminium pretreatment processes

are characterised by a simple process control and can also be used in spraying, dipping or cascade

processes. The baths of the stable, low-sensitivity processes are easy to control online and are

characterised by low maintenance requirements. With simple "quick tests", all alternative chromium-

free coatings from Chemetall can be determined both by XRF (X-ray fluorescence analysis) and with

qualitative and quantitative methods.

4.2.4 Perfect surfaces with Gardobond® X 4661

If, in addition to high corrosion, high optical performance is also required, then many conventional

processes show their limitations. An example is the sheened and polished surfaces of alloy wheels. In

this area, the chromium-free Gardobond® X 4661 process, also known as the SAM process, shows

the best properties, because it has optically neutral behaviour towards the surface. Even on profile

material used for furniture, shower enclosures, vehicle accessories and in architecture, the SAM

treatment shows very good test results. The abbreviation SAM stands for Self-Assembling Molecules.

At the microscopic level, the SAM molecules form a homogeneous, monomolecular film on the

metallic surface, which leads to a very good corrosion protection and ensures excellent paint

adhesion. Since the chemical reaction takes place in a few seconds, very high production rates can be

achieved, which increase plant productivity. Chemetall is a leading supplier of chromium-free

pretreatment processes for aluminium wheels, with more than 60 customers worldwide.

In addition, the SAM process can be used, depending on the application area, usually without

significant plant-specific adaptations. The process sequence and the number of baths do not generally

change. The process is very robust; the checking may be performed by means of electrical

conductivity and pH value. SAM levels can also be directly determined with a photometer.

23

4.2.5 Permatreat® 1903 for the food industry

Since the turn of the millennium, many food and beverage and can makers have switched to another

chromium-free alternative from Chemetall: Permatreat® 1903. Excellent properties in terms of

corrosion protection and adhesion and compatibility with a variety of different paint systems make this

a very flexible and attractive process. The quality of the coating surpasses to some extent the level of

the chromium (III)-containing predecessor. Both in the conventional dipping process and in the no-

rinse process, the can lids that require increased corrosion resistance, can be pretreated. Permatreat®

1903 is certified by the Nehring Institute (testing of elution) as well as by many leading can

manufacturers such as Ball, Impress and Crown, to name just a few. With only minor modifications,

Permatreat® 1903 can be used in all conventional food and beverage canning lines.

4.2.6 A true multimetal-ready alternative

Looking beyond aluminium pretreatment, multimetal capability is today becoming increasingly

important. In the automotive industry, the growing material mix in the bodywork and components

demands greater flexibility; in the electronics, the electrical current flows in ever finer and narrower

tracks, and all materials are continuously exposed to higher stresses. Process-related disadvantages

of phosphating, such as hydrogen evolution, which can lead to material embrittlement or the increase

in electrical resistance in the blank corrosion protection, are therefore more and more difficult to

overcome. In this context, the silane-based OXSILAN®technology has proven itself to be technically

superior:

Oxsilan® is multimetal-readyall

common metals and alloys can be treated (steel, cast steel, galvanised steel, aluminium,

magnesium, etc.)

Oxsilan® is environmentally friendly

- No hazardous heavy metals such as nickel

- Low water consumption (multiple use of rinse water is possible)

- Virtually no sludge production

- Very low waste disposal costs

- Simple wastewater treatment

24

High economic efficiency

- Sparing on material requirements (thin layers)

- Energy-saving (room temperature)

- Fewer process steps (no activation or passivation steps, rinsing steps may be

omitted in some cases)

- - Low disposal costs (no heavy metals)

Short treatment times (increased productivity)

Simple and robust chemistry, stable process

For job coaters, the multimetal capability plays an important role. Motor housing made from aluminium,

steel axle parts, roof rails made from stainless steel or magnesium-containing instrument panel

supports must pass through the pretreatment baths in the shortest possible cycle times. This change

represents a major challenge to phosphating. With OXSILAN®, all common metals in the automotive

industry and in the E/E and construction industry, such as steel, stainless steel, aluminium or

magnesium alloys and cast steel, can be pretreated. Another major advantage of this silane-based

technology proves to be the lot operation mode. This allows pure aluminium components to be

implemented over a longer period. Chemetall offers job coaters who want to completely dispense with

a bath exchange, depending on the required quality level, an OXSILAN® system that can pretreat the

entire variety of substrates in a single bath.

More than 300 companies, of which 50 are in the automotive industry, today use OXSILAN®

worldwide. Since 2009, this new thin-film technology is used increasingly in bodywork pretreatment.

Meanwhile Daimler, Opel, PSA, Renault and Hyundai in various plants have converted their

component or bodywork pretreatment to OXSILAN®. Compromises in terms of process reliability,

quality, durability, delivery punctuality or costs are unacceptable in this highly competitive market. The

fact that this process has still been able to prevail across the board speaks volumes. Finally, practice

has shown that the conversion is economically worthwhile. A comparison of relative costs calculated

from average values illustrates this. The sometimes dramatically lower costs for energy and waste

disposal should have an even stronger effect in the coming years, because even optimists are not

anticipating lower prices in this area.

25

Zinc phosphating OXSILAN® process

Heating costs 100 60

Electrical energy 100 70

Rinsing water 100 30

Waste removal 100 15

Maintenance costs 100 20

Table: Comparison of relative costs (average values)

The switch to the chromium-free OXSILAN® process often reduces costs. The sometimes dramatically

lower costs for energy and waste disposal should have an even stronger effect in the coming years.

4.2.7 Conclusion & outlook

It is understandable and legitimate that user of chromium technologies will attempt to obtain an

extension of the grace period. Objectively, however, there is no doubt that this transitional period will

have a tendency to come to an end. Other niches in the industrial use of chromium are also likely to

disappear gradually. Fortunately, optimally functional replacement technologies have long been

established, which neither in quality nor in costs or availability are inferior to the chromium-containing

process. The opposite is much more often the case: The conversion is often achieved quickly, easily

and without significant costs. There are also attractive savings, because all of the presented

alternative technologies offer a simpler and more stable processes and lower energy consumption.

Since all processes are free of heavy metals, the costs of waste water and refuse treatment are also

reduced. Persisting with the outdated and harmful technology is perhaps understandable, but this

position is not rational.

26

4.3 Henkel KGaA, D-Düsseldorf

Modern alloy coatings are highly specialised processes that must meet a wide variety of different

requirements. Along with high-performance corrosion protection, for metal processing companies the

use of environmentally friendly production processes increasingly plays an important role. As a

specialist in surface coatings, Henkel, with its broad product portfolio, sets industry-wide standards.

Under the Alodine brand, the company presented, at the ALUMINIUM 2010 fair, sustainable coating

technologies that combine the highest quality with responsibility towards people and the environment.

At ALUMINIUM 2010, Henkel was represented as a technology leader in the field of surface

pretreatment with its own stand. Under the slogan "One Source For All Needs - Alles aus einer Hand",

the company presented itself as a competent partner that, under the Alodine brand, offers innovative

technologies for pretreatment of aluminium prior to painting. These are equal to the constantly

changing demands of the aluminium industry and ensure maximum corrosion protection with minimal

environmental impact.

4.3.1 Alodine 400 - Chromium-free coating without sacrificing quality

With its chromium-free Alodine 400 process, for example, Henkel presents a process for the

pretreatment of aluminium surfaces that will not only improve environmental performance and

occupational health and safety, but also fulfils the high quality requirements in terms of paint adhesion

and corrosion resistance of powder coated materials. The use of this technology, which is exempt

from labelling requirements, offers businesses the advantage of being able to completely dispense

with conventional wastewater treatment, since the process does not involve any heavy metals. At the

same time, the plant operator also benefits from improved employee safety.

Practical experience confirms the high quality of the chromium-free process. Thus, on the metallic

surface, a transparent titanium-based conversion coating is generated that durably protects the

powder-coated parts provides against corrosion and, as an adhesion substrate, improves the

subsequent paint application. The modern conversion process of Alodine 400 has GSB International

and Qualicoat certification, thus offering ideal conditions for a long-term weather-resistant powder

coating.

27

4.3.2 Alodine 5992 - corrosion protection for unpainted surfaces

Another new development in the field of metal pretreatment is Alodine 5992. In contrast to toxic

chromium (VI)-containing passivations, the conversion coating produced by this process is based on

non-toxic chromium (III) compounds. In view of the many regulatory requirements, such as the ROHS,

WEEE and ELV directives, Alodine 5992 represents a real alternative to traditional conversion

treatments. The trivalent layer of an equivalent blank metal corrosion resistance for unpainted

aluminium surfaces, as well as an optimal adhesion substrate for application of paint; the powder-

coated aluminium parts have the same corrosion protection as yellow chromated sheets and profiles.

Alodine 5992 is Qualicoat certified and also meets the MIL requirements for use in the aerospace

industry. Moreover, the use of the process facilitates wastewater treatment and disposal, since the

reduction of hexavalent chromium to the trivalent form is not necessary.

Under the Alodine brand, Henkel is developing modern and sustainable coating technologies for pretreatment of aluminium surfaces.

28

4.4 MacDermid GmbH, D-Forst

The MacDermid company offers various alternative pretreatment processes. These have been used

for many years in numerous factories in Germany and other European countries.

The performance of the systems offered by MacDermid has been documented in numerous studies

and also by certifications from various quality communities (including GSB International). An overview

of the various systems and their certifications and properties is shown in the following table.

Of crucial importance for the performance of MacDermid's alternative systems is compliance with

prescribed rinse criteria in the rinsing before - and in the event that downstream rinsing is required -

after the actual conversion bath. Contamination with foreign materials must be avoided. Similarly, a

corresponding bath analysis and process monitoring is recommended. The specific and balanced

combination of MacDermid process chemicals leads to a significant reduction in the process costs of

the pretreatment (in direct comparison to conventional chromating processes). All MacDermid

processes are suitable for dipping and spraying applications. In particular, Iridite CF is also suitable for

a multimetal pretreatment prior to powder coating.

Overview of MacDermid pretreatment processes:

Product name: Basis No-rinse

process Certifications Number of

reference systems Specifics

Iridite EXD Zr No GSB International (stage 3

pending)

Qualicoat

Customer-specific

10 Purely inorganic composition

Special drying behaviour

Particularly suited to polyamide thermal seals

Iridite CF Ti/Zr Yes GSB International

Qualicoat

Customer-specific

15 Multimetal capability

No after-rinsing required

High bath stability

Iridite NCP Ti/Zr No Qualicoat

Customer-specific 3 Blank corrosion protection

Iridite NR2-I Ti/Zr Yes Qualicoat

Customer-specific 10 Coil Coating

Iridite NR4-T Ti/Zr Yes With integrated UV tracer

In the test phase

29

4.5 Nabu-Oberflächentechnik GmbH, D-Stulln-Nabburg

4.5.1 Chromium-free pretreatment with Nabutan 310

As is so often the case, Germany seems to ahead of the game when it comes to introducing

environmentally sound processes. For more than 10 years, therefore, chromium-free pretreatment

processes have been established on the market, meaning that various practical processes are now

available. Chromium-free pretreatment due to the ROHS Directive, the EU ELV Directive or regional

regulations, has today become a real alternative to yellow or green chromating.

What exactly is meant by "chromium-free pretreatment with Nabutan 310"?

Chromium-free pretreatment means: The passivation of the aluminium surface without chromium (VI)

or chromium (III) compounds in the bath and in the deposited conversion coating that is applied to

promote adhesion and inhibit corrosion. Of course, in these processes, the degreasing and pickling

process is also chromium-free. Before the powder coating, the aluminium profiles are not protected by

standard yellow or green chromating, but are subjected to a titanium- and polymer-containing

pretreatment, which is 100% free of toxic, carcinogenic chromates.

With a classic yellow chromating, the application parameters are clearly known and defined. The

operator estimates the low-maintenance bath control and the uncomplicated application. On the other

hand, the environmental incompatibility or the dangers of chromium (VI) to humans must not be

underestimated. The recurring debate on this serious issue should continue to incite us to reflection in

the future. If it were merely a matter of technical merits, then yellow or green chromating would be

hard to beat. They always pose a challenge to chromium-free alternative systems.

30

With the awarding of the contract, the contractor or architect, as the user of coated aluminium profiles

and sheet materials, can decide whether to select a traditional "yellow chromating" as the corrosion

protection or an environmentally friendly chromium-free pretreatment with Nabutan 310, which is

almost equal in all respects to chromate pretreatment.

4.5.2 Certification testing for Nabutan 310

No new product group in recent years has been more carefully tested than chromium-free conversion

layer formers. In addition to leading quality organisations, façade builders, pressing plants, automobile

manufacturers and research institutes have been working with chromium-free conversion layers from

individual providers. In the example of Nabutan 310, the previous quality assessments are collected.

When properly applied, they give the operator the confidence to meet the high demands of the market.

4.5.3 Approval in the process regulation 92049 BMW Group

BMW approved the titanium-based pretreatment process with Nabutan 310 for the pretreatment of

aluminium casting alloys and aluminium wrought alloys in 2004.

4.5.4 Qualicoat Product Approval

Nabutan 310 was tested in 2003 by Qualicoat and received approval as an alternative pretreatment.

The repeat tests have so far all been completed positively.

4.5.5 GSB International quality community

In 1998, the product Nabutan 310 received the provisional certification from GSB International

according to GSB International Stage 3 of the material certification process for the powder coatings

sector. Under certification number 302 a, after a three-year exposure without any problems, the final

certification was issued in 2002. The recurring annual tests from the current production lines have all

been passed to date.

31

4.5.6 Results from 10 years of exposure at Hoek van Holland

In 1998, GSB International exposed chromium-free pretreated and coated plates at Hoek van Holland,

a suburb of Rotterdam. The prevailing maritime industrial climate there is ideally suited for exposing

the powder paint-coated aluminium samples to weathering tests.

The Nabutan 310-pretreated plate and profile sections, even after 10 years of exposure, still showed

no significant signs of corrosion or adhesion problems. In Hoek van Holland, where the samples were

exposed to intense sun and aggressive sea air, the reliability of the Nabutan 310 system was

confirmed.

Image: Weathering in Hoek van Holland, NL

The plate and profile sections originated from a plant test of GSB International Stage 3, performed

under production conditions at a GSB International coating company. The test results in the short-term

studies, such as ESS and FFK, essentially confirm the results of the exposure at Hoek van Holland

over a period of 10 years. This shows that environmentally friendly processes do not need to be a step

backwards, and there is now enough experience to apply the alternative processes correctly.

32

4.5.7 Summary

The use of chromium-free alternatives does not necessarily mean sacrificing quality. With proper use

of the product, the corrosion protection is similar to that of a conventional chromating. In contrast to

chromating, Nabutan 310 poses no problems for the environment, and is thus easier in terms of the

storage and handling of chemicals. However, the superior environmental performance is accompanied

by a higher sensitivity of the process, which often means that alternative pretreatments are unjustly

labelled as being complicated.

In fact, with a chromium-free process, users get a somewhat lower flexibility and sometimes even

more sensitivity in the pretreatment process. Thus, the operation mode of galvanised steel and

aluminium in the same pretreatment chemistry is critical. But even with the use of yellow or green

chromating, a mixed operation mode can lead to unwanted electrochemical depositions on the

aluminium material and negatively affect the corrosion protection. Care is therefore recommended for

any type of chemical pretreatment.

If the chromium-free pretreatment process is well monitored, the bath chemistry including rinsing is

analysed, and the chemical additions are automated as far as possible with control units, this

sensitivity can be counteracted. It is precisely these measures that lead to a more intensive process

control, which ultimately contributes to an increase in quality.

33

4.6 SurTec International GmbH, D-Bensheim

SurTec 650 is certified by GSB International as an alternative pretreatment system with chromate-free

layers under certification number 308 a. It has been used since 2005 in the non-construction sector

and since 2008 in the construction sector in Germany. SurTec 650 meets the requirements for

corrosion testing in the Sea Proof Plus weathering class (FFK: F = 0, 1000 h) and is therefore ideally

suited for mass production at the highest level of quality.

In addition to the relevant standards for the construction industry, the requirements of the aerospace

industry (e.g. blank corrosion in the salt spray test > 168 h), the electronics industry (e.g. surface

resistance) and the automotive are met; for this reason, SurTec 650 is also optimally suited for coaters

with a large variety of products. The product SurTec 650 is exempt from labelling requirements.

Precise bath control is possible via a simple analysis of the active substance by means of photometry.

SurTec 650 is a never-dump process; therefore, no new preparation of a bath solution is necessary.

By replacing chromium (VI) technology with SurTec 650, process cost savings of up to 30% can be

realised.

34

5 The current development status of chromium-free processes from the perspective of the

coaters

5.1 General information

The following contributions reflect the opinions and experiences of the companies. The

content is solely the responsibility of the coaters.

GSB International currently has 80 coaters as members, 33 companies of which use chromate-free

and chromium-free surface pretreatments. The following examples describe some past experience in

the use of chromium-free pretreatment processes.

35

5.2 Alulux Beckhoff GmbH & Co., D-Verl

Alulux is one of the world's leading manufacturers of roller shutters and garage door systems made of

aluminium. The prefabricated shutter and garage door brands are optimally tailored to the needs of

specialist customers. Longevity, the use of high-quality materials and the development of individual

solutions are natural requirements. Production to precise dimensions and also the comfort automation

of the roller shutters and garage door systems are performed entirely according to requirements.

Since 2002, in the prestage to the powder coating, Alulux has been using a chromium-free surface

pretreatment from the company NABU.

The process steps are degreasing, rinsing, pickling, fully desalinated water rinsing, and chromium-free

conversion coating.

The experiences with chromium-free preanodising have been entirely positive and have met with

strong recognition from the Alulux clientele.

Some building images:

36

5.3 Alumil-Milonas Aluminium Industry S.A., GR-Kilkis

In early 2008, the company Alumil began to use the chromium-free pretreatment as a conversion layer

for powder coating in its horizontal and vertical coating plant for aluminium profiles.

From the beginning until now, products from different suppliers were used both in the horizontal and

vertical plants, which are constantly being tested and evaluated during production. All these products

have a certification from GSB International and Qualicoat.

Pretreated and coated amounts:

In parallel to the production process, laboratory tests and evaluations are conducted to obtain data for

the optimal operating conditions; emerging problems can also be analysed here.

Horizontal system      

Year Experiment time Chemical

manufacturer Product Pretreated quantities (kg)

2008  2 months A 1  750.000 

2008  3 months B 1  1.150.000 

2008  3.5 months C 1  860.000 

2009  5 months C 1  1.200.000 

2009  3 months B 1  580.000 

2009  4 months A 2  950.000 

2010  12 months A 2  2.250.000 

2011  2 months D 2  100.000 

2011  7 months A 2  670.000 

         

Vertical system      

Year Experiment time Chemical

manufacturer Product Pretreated quantities (kg)

2008  4 months E 1  4.500.000 

2008  8 months A 2  5.750.000 

2009  12 months A 2  7.000.000 

2010  10 months A 2  5.600.000 

2010  2 months E 2  1.400.000 

2011  2 months A 2  950.000 

2011  6.5 months E 2  5.000.000 

2011  0.5 months D 2  380.000 

37

Our previous experience with the use of a chromium-free pretreatment are:

1. It is important that the supplier knows his product perfectly.

2. A crucial factor is the adjustment of the product application to the particular characteristics of

the production line.

3. The properties of the coating, apart from the chemical process, seem to have significant

influences on the painted end product.

4. The user must have both a well-equipped laboratory with all necessary equipment and also

well-trained personnel.

5. The user must ensure a continuous and systematic bath monitoring of the product parameters

(concentration, conductivity, pH, temperature, coating weight, etc.).

6. Each coating line should be equipped with the necessary equipment (dosing pumps,

conductivity, pH, cooling and heating, etc.) to ensure the stability of the product.

7. The use of newly certified products alone does not ensure smooth execution.

Some of our objects that have undergone chromium-free pretreatment since 2008:

Image: Blue Ridge - India Image: Seaside Hotel in Sirte - Libya

38

Image: Khan Shatyr Project - Kazakhstan

Image: American University - Iraq

39

Image: Jasmin Tower - Katar Image: Reem Tower in Abu Dhabi - UAE

40

5.4 heroal – Aluminiumgesellschaft Hövelhof mbH & Co. KG, D-Verl

The company heroal is a GSB International premium coater and operates three coating lines, of which

two plants work with yellow chromating and one plant works with a chromium-free surface

pretreatment. Chromium-free passivation has been in use for about 2 years in the painting plants,

aluminium is coated exclusively. Since the introduction of the chromium-free surface pretreatment in

the plant, well over 500,000 m2 of chromium-free pretreated aluminium profiles have been coated. The

dosing technology in all areas of the pretreatment is an important point for product safety. Another

important point is to control and document the bath parameters.

It is already clear that, in the future, even more objects will be tendered for chromium-free

pretreatment, so the company heroal is well prepared if the legislator prohibits the use of chromium

(VI).

Another advantage of the introduction of chromium-free pretreatment is that there are no longer any

expenses for chromium-containing waste water; we also protect our employees and contribute to the

environment.

Already, a new coating plant with chromium-free passivation is being planned, resulting in reduced

regulatory requirements for obtaining the operating licence.

41

5.5 LOV-Limbacher Oberflächenveredelung GmbH, D-Limbach-Oberfrohna

More than 12 years of practical experience with chromium-free passivation in spraying processes at

LOV.

Authors: Dipl.-Ing. Michael Kirmse (GF), Dipl.-Ing. Jörg Seiche (QMB)

5.5.1 Introduction

Limbacher Oberflächenveredelung GmbH is today a medium-sized enterprise in the field of powder

coating and industrial wet painting with 40 employees. Since its foundation in 1998, the company has

grown from a workshop into a high-quality industrial enterprise. The most important milestones in this

context were the attainment of product qualification for outdoor aluminium according to DB TL 918340

(certification for rail vehicles) in 2003, the certification according to ISO/TS 16949 in 2004 and joining

GSB International in 2009 as a master coater. In addition, LOV GmbH is a founding member of the

IQC. These certificates and approvals constitute evidence of quality by external monitoring, which

provides each customer with reassurance regarding the coating of its products.

This includes the continuous improvement of processes and workflows. This led in 2008 to a new

investment at the Limbacher Oberflächenveredlung site. As part of this new building, one of the most

advanced coating plants in Europe was constructed. In doing so, the very latest technology was

implemented. Highlights worthy of mention include: a highly flexible power-and-free conveyor system,

a trication zinc phosphating for the pretreatment of steel or galvanised steel, a chromium-free

passivation for aluminium (retaining the same technology as the previous plant) with the highest

possible corrosion requirements and coating in two ultramodern powder coating booths.

42

Image: 2-part pretreatment plant LOV Image: Pretreatment testing LOV

Image: Powder coating line of LOV with two powder booths

5.5.2 Chromium-free passivation

As already mentioned, LOV GmbH can look back on over 12 years' experience with chromium-free

passivation and was a pioneer in the Europe-wide trend towards conversion to Cr (VI)-free

pretreatment systems. As early as 1999, it already ensured that the system to be used met the

guidelines of GSB International. This product based on titanium and polymer is completely chromium-

free passivation, which also satisfies the ROHS Directive and the EU Directive on ELVs, and has been

used in LOV from the start as a no-rinse system.

43

In contrast to classical chromating systems, chromium-free systems, however, place much greater

demands on monitoring (titration, shift weight determination, conductivity) and bath maintenance of the

active and also the rinsing baths. Of particular note here is that the coating weight determination, due

to the small layer thickness in the nanometre range, is not performed by weighing-out, as in classical

systems, but is done photometrically. This method is also more accurate, meaning that there is less

room for error. Since the chromium-free passivation itself produces virtually no pickling attack on

aluminium, the optimal effect of the pickling degreasing must also be observed here.

In addition, these systems react very sensitively to carryovers, especially with foreign ions, which then

generally lead to immediate rejection of the passivation chemistry. Therefore, these systems are only

very limitedly or not at all suitable for a mixed mode of operation with metals other than aluminium.

Equally important is the production of an optimal rinsing criterion prior to passivation.

44

It is important in this regard to make sure that rinse 1 is not too clean, i.e. conductance in this rinse is

too low. Furthermore, the conductance in the fully desalinated water circulation rinse with maximum 10

µS may not be exceeded, since this would otherwise result in an excessive load on the surface with

foreign ions and hence a deterioration in the corrosion resistance.

These conditions have been established at LOV since 1999 and we have thereby gained the

experience that, when the right conditions are present, results are achieved which are absolutely

equal to those achieved with classical systems.

In the new investment in 2008, we incorporated these experiences into the planning of the

pretreatment plant. This was done in detail by the following measures:

Creation of a separate pretreatment line for aluminium only

Creation of defined overflows into the active baths pickling degreasing and passivation

Automatic addition of the preparation chemicals to the active baths

Consistent setting of a defined cascade between the rinsing 1 and rinsing 2

Fully desalinated water rinsing not as a basin rinse, but by direct loading of the parts via their

own spray register with direct outflow to water treatment via an ion exchange system

These additional measures subsequently turned out to be extremely positive. Because of the constant

overflow of the pickling degreasing, complete rejections are no longer necessary. Only partial

rejections occur in the regular cleaning work as part of predictive maintenance. In addition, the

passivation has an almost infinite lifetime due to these measures. Only for cleaning the bath walls is

draining off of the passivation into the opposite container necessary, whereby the chemical is 100%

pumped back in after cleaning.

With regard to corrosion resistance, our chromium-free passivation based on titanium/polymer met our

customers' requirements in nearly 100% of application cases. In addition, with its passivation system,

LOV GmbH has met the criteria of the Sea Proof Plus seal of GSB International without further ado,

which underlines the impressive performance of this system.

45

5.5.3 Examples of implemented projects:

Image: Representative office building in the centre of D-Chemnitz/Saxony

Image: Library Of Birmingham (Facade manufacturer: Lindner Fassaden GmbH, D-Arnstorf)

46

5.6 TK-Oberfläche GmbH, D-Bielefeld and PBS Schreiner GmbH & Co. KG, D-Grebenau

We have more than 12 years of practical experience with a chromium-free surface treatment in dipping

and spraying processes, which are certified by GSB International.

5.6.1 Introduction

Because of the changes in the 1980s with regard to the environment and corrosion requirements for

powder-coated parts used outdoors, intensive research efforts were undertaken especially in the field

of pretreatment.

It was foreseeable that existing systems, such as chromating and phosphating, were no longer able to

meet all of the requirements of the industry. The results of the nearly 10 years of developments in the

field of chromium-free pretreatments could then be transferred to a pilot phase or customer trials at the

end of the last millennium.

5.6.2 Process description

Process sequence for alkaline dipping:

Process sequence for alkaline spraying:

TK-Oberfläche company PBS Schreiner company

Alkaline etching degreasing Alkaline etching degreasing

Coil 1 Coil 1

Coil 2 Coil 2

Fully desalinated water coil Coil 3

Desmutting Desmutting

Coil 1 Coil 1

Coil 2 Fully desalinated water coil 1

Fully desalinated water coil Fully desalinated water coil 2

Fully desalinated water coil 3

Chromium-free conversion Based on titanium

Chromium-free conversion Based on titanium

Process sequence for dipping (left) and spraying pretreatment (right)

47

As with almost all surface-finishing processes, pretreatment consists of the steps of degreasing,

etching/desmutting/activation (adhesion creation and corrosion protection), which are interrupted by

rinsing steps. In the case of chromium-free pretreatment - in comparison to other passivations - extra

attention must be paid to the rinse steps, since the success of the process is extremely vulnerable to

contaminants. Ultimately, by observing all of the process parameters, we can obtain a homogeneous

titanium fluoride polymer layer on an aluminium component, which serves as the optimal substrate

with extremely good corrosion protection properties for a subsequent layer of powder.

The almost unlimited service life of the chromium-free process (only partial rejections are necessary if

properly maintained) not only reduces disposal costs and environmental risks but also considerably

reduces the cleaning required and the health risks to employees.

Image: Scanning electron micrograph images (left) and top view of chromium-free layer (right)

To the chromium-free pretreated profiles, in a powder booth, a 50-120 μm thick layer of powder

(selected according to requirements) is applied by spray guns (corona or tribological loading) and

cross-linked (fused) by annealing at approx. 200 °C. In this way, aluminium components can be given

corrosion protection that meets the GSB International requirements for resistance to filiform corrosion

(DIN EN 3665) as well as the tests in the acetic acid salt spray test (DIN EN ISO 9227).

Image: Example of a powder booth The following image shows the schematic structure of a powder-coated component. Here, the small

layer thickness of the effective chromium-free coating is remarkable.

48

Image: Schematic representation of a powder coating on aluminium

Image: Photometric measurement principle for layer weight determination 5.6.3 Testing criteria

The introduction of a chromium-free pretreatment must - due to its specific needs - lead to a changed

working method for a coating company.

For example, test panels must be operated regularly with production batches in which, by cross-

cutting and boiling test, Erichsen cupping, mandrel bending test and cutting test, and a 1000 h ESS

test (DIN EN ISO 9227), both adhesion and corrosion protection are checked. Appropriate tests and

their results are shown in the image below. In addition, the correct setting of the bath chemistry must

be determined regularly. This is ideally done by a determination of the deposited layer thickness. As

an auxiliary measure, we here determine the layer weight. In the next image, the sequence of the

photometric determination is shown schematically. Alternatively, a determination by XRF can also be

performed (X-ray fluorescence analysis) with which we only determine the amount of deposited

titanium.

49

Image: Test panels after adhesion test (left) and profile section after 1000 h ESS (right)

5.6.4 Summary and outlook

Looking back on more than 12 years of successful work with a chromium-free no-rinse pretreatment in

mass production, it can be said that not only is it equal to the current chromating and phosphating in

respect of its process safety and properties, but even constitutes enhanced protection, also supported

by improved environmental and employee protection and lower disposal costs.

Through the combination of a chromium-free pretreatment with highly weather-resistant or PFTE-

containing powder coatings, we at TK-Oberfläche GmbH and Schreiner GmbH & Co. KG can offer our

customers the best and also the most environmentally friendly powder coating in the market. In this

context, all of the relevant EU directives on the EU ELV directive and the ROHS or WEEE (popularly

known as the "e-waste regulation") are fulfilled, even for the construction industry. With this

combination, there are now only a few other companies in Europe in the industry who can offer their

customers these two advantages together.

Therefore, in all respects, it is a successful process introduction. The following images of the buildings

equipped with our coating stand as living witnesses to the very positive experiences since the process

conversion, with which our courage was rewarded.

50

Property images:

Image: University Clinic of Mainz (PBS Schreiner, D-Grebenau)

Image: University Clinic of Frankfurt-am-Main (PBS Schreiner, D-Grebenau)

51

Image: DonStroy, Moscow (TK-Oberfläche, D-Bielefeld)

Image: Mövenpick Hotel, NL-Amsterdam City Center (TK-Oberfläche, D-Bielefeld)

52

5.7 Warema Renkhoff SE, D-Marktheidenfeld

Warema Renkhoff SE operates 2 powder coating lines, each equipped with a 6-chamber cycle plant

for pretreatment.

The pretreatment involves the following process steps: Alkaline pickling degreasing, acid pickling,

passivation, and the necessary rinsing steps. Until the end of 2008, a yellow chromating was used for

passivation.

Due to the increasing demand for chromium-free pretreated surfaces, the many years of positive

testimonials for chromium-free surfaces, the prohibition of chromium (VI) compounds in the automotive

industry and electrical engineering and the associated uncertainty in the market regarding chromium

(VI) certifications, Warema Renkhoff decided to convert to chromium-free pretreatment in the new year

2008/2009.

Since the two pretreatment plants possessed a common fresh water supply, rinsing water preparation

and waste water processing, it made sense to make the switch in the pretreatment on both plants

simultaneously.

The plant cleaning, which must be done very laboriously and thoroughly in the conversion, was

performed together with the company Buchen Umweltservice GmbH. In the first step, the adherent

chromate compounds were partially dissolved with sodium hydroxide and hydrogen peroxide and then

the remaining encrustations on the plant were removed by means of high-pressure cleaning and

rinsing. The resulting highly concentrated waste water from the cleaning was disposed of externally,

and all other effluent was treated in the company's own waste water system.

To ensure the absolute purity of the surfaces before the chromium-free pretreatment, the rinsing water

ducts in the pretreatment plant were rebuilt. Since the chromium-free pretreatment is used as a no-

rinse process, a chamber for an additional rinsing process was available. Thus, it is possible to

operate the pretreatment with 2 rinsing chambers (containing multiple rinsing steps) between acid

pickling and chromium-free passivation. The carryover of foreign ions into the chromium-free

passivation bath is almost impossible, thus forming the basis for good and reliable corrosion

protection.

The control of the passivation layer can be performed with simple tools in the company laboratory. On

site, additional control and monitoring measurements were installed to stop the pretreatment

immediately if the chromium-free passivation process is disrupted.

53

This ensures that all parts are given the necessary corrosion protection, which is not optically visible,

in contrast to yellow chromating.

A decisive advantage after the switch to chromium-free pretreatment was improved corrosion

protection of the surfaces against filiform corrosion.

Furthermore, the waste water system became more flexible, since all waste water could be processed

either in one or the other waste water plant.

Due to the increased purity requirements in the pretreatment, more fresh water was consumed and

thus more waste water accumulated, but the specific consumption of waste water chemicals and

specific sludge accumulation were lower than with the use of chromating. The fully desalinated water

plants for the preparation of the rinse water can be operated for longer until a regeneration is required,

because the rinse water is less contaminated. And, of course, it must not be forgotten that the staff is

spared from handling hazardous chromium compounds.

Meantime, Warema Renkhoff SE has an impressive number of objects that are equipped with sun

protection products with chromium-free pretreated surfaces.

Some object examples:

54

55

6 Chromium-free pretreatment for coil coating

6.1 Hydro Aluminium Rolled Products GmbH, D-Grevenbroich and Novelis Deutschland

GmbH, D-Göttingen

The following contributions reflect the opinions and experiences of the companies. The content is

solely the responsibility of the company.

6.1.1 General information

In the coil coating process, rolled coils of aluminium are continuously coated with paint or foil. After

coating, they are re-rolled into coils, and then cut with a processor according to their use as a roof or

wall panel, window profile, blinds, signs, etc., cut, die-cut, profiled, deep-drawn, jointed or glued

together.

Aluminium surfaces must be protected against corrosion prior to painting by a suitable chemical

pretreatment. For decades, chromate-containing chemicals were used for this surface treatment.

Since these are classified as hazardous to health, carcinogenic and harmful to the environment,

chromate-free and chromium-free systems have been in development in the coil coating industry since

the 1980s. Chromium-free pretreatments and chromate-free primers have been available on the

market since the mid-1990s.

Coil-coated aluminium is used in general industry, but in larger quantities also in the packaging

industry. Here, chromium-free processes were in use in some fields as early as the 1970s. The

following discussion refers to the industrial application, however. The use of coil-coated aluminium as

packaging is not discussed here.

In the field of general industry, the construction industry is the largest market for coil coating,

accounting for around 70%. Therefore, this discussion will be restricted to that segment.

Regarding a survey of construction companies and coil coating processors, as reported by GE Betz in

November 2002 at the Congress of the European Coil Coating Association (ECCA) in Brussels (David

Ellis, GE Betz, "Chrome Use In Building Products: An Industry Perspective") it was already apparent in

2002 that two thirds of all respondents after the first evaluation of the results with chromium-free

coatings assumed that the quality of chromium-free coated plates was comparable to that of

chromate-containing plates, and chromium-free coatings would become widespread in the future. At

that time, chromium-free pretreatments had been on the market for about 6 years.

56

Since 1994, chromium-free primers on steel or galvanised steel have been used in the coil coating

industry. In 1997/98, this was followed by the introduction of chromium-free pretreatments in the steel

industry.

In the aluminium industry, due to the specific properties of aluminium, chromium-free systems have

already been known for even longer.

The details presented here regarding chromium-free coatings in the coil coating industry are mainly

based on the results of a project developed by the ECCA Group in Germany, under the leadership of

Marcus Schinzel, of Chemetall, in late 2005.

6.1.2 The coil coating process

6.1.2.1 Overview

Aluminium products made from coil-coated coils and sheets are characterised by consistent quality,

exceptional formability, corrosion resistance and abrasion resistance, and a variety of colours, gloss

levels and surface textures. The production process typically involves the following steps:

Cleaning

Conversion treatment (pretreatment)

Possibly the application of a primer

Top coating or film coating

6.1.2.2 Cleaning and degreasing

The coil coating process requires a clean, well-prepared surface of the metal coil, if a long-life product

is to be created that has an aesthetic appearance and high durability in all environmental conditions.

Cleaning and pretreatment of the coil are performed in separate zones of the coil-coating system

immediately before coating.

The cleaning of aluminium coils includes both alkaline and acidic cleaning steps. The cleaners remove

corrosion products and release agent residues from the surface and ensure that the surface is

wettable. Two rinsing steps followed by an acid pickling, often based on sulphuric acid and fluorides.

In this step, the oxide layer and accumulations are removed from the alloy components. The strength

of pickling attack is controlled by the fluoride concentration. In the final step of cleaning, the excess

cleaner is removed by means of nip rolls and thoroughly rinsed with water in several stages.

57

6.1.2.3 Chromium-free surface pretreatment

As soon as the cleaning process has created a clean, water-wettable surface, the now highly reactive

metallic surface must now be covered with an anti-corrosion layer, which also provides an adhesive

substrate for the subsequent paint layer. This is achieved by chemical processes for the conversion

treatment of the metal surfaces.

Chromium-free pretreatment chemicals nowadays offer adequate corrosion protection and adhesion

for subsequent coatings. Strong correlations and the comparability of chromium-free and chromate-

containing pretreatments in various natural weathering and accelerated corrosion tests have been

reported.

In general, the chromium-free chemicals are based on aqueous solutions of transition metal

complexes and compounds, for example, titanium and zirconium compounds, as well as on specific

water-soluble polymers. They generate defined layers that can be characterised analytically, e.g. by

means of Auger electron and photoelectron spectroscopy.

The mechanisms of adhesion and corrosion resistance are attributed to a metal oxide layer that forms

in a first reaction phase on the treated sheet and is then covered with the organic matrix.

Pretreatment solutions are applied by spraying, dipping, or dipping/squeezing. More frequently,

however, the no-rinse process is used today. Here, a liquid film only a few micrometres thick is applied

to the coil with a roller. This film is dried, thus forming a corrosion-protective, adhesion-promoting solid

layer. In the application by means of a roller coater, there are no excess chemicals or products of

secondary reactions on the surface, which eliminates any need for subsequent rinsing. This in turn

eliminates the need for huge amounts of rinse water and its disposal issues.

Pretreatment procedure Chemical basis Application Overflow

approx. 10-100 l/h

Rinse chromating Cr(VI) / H3PO4 / HF Spraying/dipping + squeezing + rinse Yes

No-Rinse chromating Cr(VI) / Cr(III) / (SiO2) Chemcoater or spraying/dipping +

squeezing No

Rinse chromium-free H2TiF6 / H2ZrF6 Spraying/dipping + squeezing + rinse Yes, but no chromium (VI)

No-rinse chromium-free H2TiF6 / H2ZrF6 / organic

chemistry

Chemcoater or spraying/dipping + squeezing

No

 

58

Pretreatment procedure Carryover

approx. 5 mL/m³

Handling Work hygiene

Rinse chromating Yes - Chromate

No-Rinse chromating No (+) Chromate, no waste water

Rinse chromium-free Yes, but no chromium (VI) + Chromate-free + waste water

No-rinse chromium-free No + Chromate-free + waste water

Table: Pretreatment processes - application / waste water technology / handling

(Source: ECCA-Gruppe Deutschland e. V., Germany)

 

The chromium-free pretreatments are based on aqueous, non-toxic transition metal complexes and

special water-soluble polymers. For the reaction, the following model was developed [Deutsche

Forschungsgesellschaft für Oberflächenbehandlung e. V., Deutsche Gesellschaft für Galvano- und

Oberflächentechnik e. V. (Veranst.): Light metal applications (Düsseldorf 2004). Düsseldorf: DFO,

2004–Report Vol. No. 57 – Wendel, T.: Vorbehandlung von Aluminium-oberflächenwerkstoffen vor

dem Fügen im Automobilbau [Pretreatment of aluminium surface materials prior to bonding in the

automotive industry] and

Schubach, P.: Chromatfreie Vorbehandlungsverfahren für Aluminiumwerkstoffe [Chromate-free

pretreatment processes for aluminium materials]. In: Galvanotechnik 92 (2001), Issue 7, pp. 1825-

1834]:

In the first reaction step, the acidic chemicals attack the surface, thus generating a metal oxide layer at

the interface. At this interface, phosphorus and crystalline lattice cations, for example metal ions, are

included, which are present in the substrate and in the pretreatment chemical The metal oxide layer

ensures adhesion and corrosion protection. It is then covered by an organic layer. The polymers

cause the fixation of the inorganic components by complexation and, secondly, form a barrier layer.

The following table shows the results of various tests, in which aluminium sheets (AA 3005) were

pretreated after an either chromate-containing or chromium-free acidic cleaning. Both panels were

then provided with two chromium-free polyester paint systems. The results show that the chromium-

free pretreated sheets have the same properties as the chromate-containing pretreated sheets. Both

systems meet the requirements with regard to corrosion protection.

59

 

Table: Comparison of the corrosion protection of chromium-free and chromate-containing

pretreated samples

(Source: Chemetall GmbH, Germany)

 

6.1.2.4 Chromium-free primers

The pretreatment prepares the metal surface for painting. As the first organic layer, a base coat is

applied, known as the primer. It serves as a bonding agent between the pretreated metal and the

colouring topcoat and controls the corrosion protection of the entire paint application.

At the end of the 1980s, chromium-free corrosion-inhibiting pigments were increasingly introduced

onto the market from the raw materials industry. It thus became possible to formulate chromium-free

primers for the coil coating industry too.

Today, modern coil coating lines make use of primers suitable for many applications due to their high

quality standards. Such universal primers are based on specific binding agents that are combined with

active corrosion-inhibiting pigments to enhance the adhesion and corrosion properties. They are

optimised to effectively adhere to any substrates, on steel as well as on aluminium. They can be

painted over with all solvent-borne topcoat types in the coil coating process.

60

6.1.3 Topcoats

The field of architecture requires special deformation properties and surface hardness, and the

outdoor area calls for corrosion and weathering resistance. For these applications, polyester,

polyurethane or HDP topcoats, PVC plastisols and PVDP topcoats can be used in an almost unlimited

range of colours.

Some colour shades, in particular older ones, are still made with lead chromates or lead-molybdenum

chromates, because in some cases the customer can accept no deviation from the original proposals.

This is especially true for colours in the yellow, red, green and brown shades.

According to REACH, lead pigments may no longer be used after 30.11.2013. For some time now,

however, there have been lead chromate-free substitute pigments with an inorganic or organic basis

(Eckhart Korona, BASF SE, "Lead-Free Pigments For Coil Coating" ECCA Congress, Brussels,

22./23.11.2010). They sometimes have a very similar colour to the original lead chromates or lead-

molybdenum chromates, but are slightly more expensive than the currently used pigments. There is

currently also difficulty in replacing the bright orange shades. Research efforts are being made in this

regard to find solutions.

6.1.4 Field reports

6.1.4.1 Aluminium roller blind coil

For aluminium roller blind coils, in the ECCA Project 2005, a comparison was made between the

standard chromium (VI)-coated and chromium-free coated coils. As can be seen in the table, there are

no differences in properties between the two samples.

Product: Roller blind coils

made from coil-painted aluminium

Alloys: AlMg0,5Mn1; AlMg1Mn0,5

61

Testing Testing

standard Standard Cr(VI) No-Rinse Cr-free pretreatment

Bonding agent base PUR/PA

(polyurethane/polyamide) PUR/PA

(polyurethane/polyamide)

Adhesion and crack

resistance at the narrow

collar (hook and drip rail)

PA 0050

T0 break-free, crack-free T0 break-free, crack-free

Heat resistance at the T-

bend DIN EN

13523-13 Unchanged Unchanged

Erichsen cupping DIN EN

13523-6 No peeling paint until metal

cracking under Tesa test No peeling paint until metal

cracking under Tesa test

Condensation water -

constant climate

(Humidity test)

DIN EN ISO

6270-2

1000 h No changes No changes

Water dipping resistance

(Waterlogging)

DIN EN

13523-9 No changes No changes

Acetic acid salt spray test

(Corrosion test)

DIN EN

135239227

1000 h

Grade 1 to 2 on undeformed

surface, incipient crack on

narrow collar and cutting edge

Grade 1 to 2 on undeformed

surface, incipient crack on

narrow collar and cutting edge

Grade 1: very good; grade 2 good; grade 3: satisfactory; grade 4: sufficient; grade 5: deficient

Table: Properties of chromate-containing and chromate-free pretreated samples

(Source: ECCA-Gruppe Deutschland e. V., Germany)

6.1.4.2 Laboratory building – Henkel KGaA, D-Düsseldorf

In 1998, during the renovation of two laboratory buildings was conducted by Henkel, a reference

building for the chromium-free coil pretreatment was created. In co-operation with the company Hydro

Aluminium Rolled Products GmbH in Grevenbroich, the aluminium façade coil and primary material for

sun protection plates were equipped with a pretreatment developed by Henkel (Alodine® NR 1453)

and coated with a monolayer high-performance polyester paint.

From the sheet material, trapezoidal panels and sun protection covers (so-called interior blinds) were

created, with which, in October 1998, the staircases and window rows on the south façade of both

62

buildings were covered. The entire surface area measured approximately 400 m² of trapezoidal panels

and 800 m² of sun protection roller blinds.

The façades have been exposed for more than 10 years to sunlight, wind and weathering in an

industrial environment, and in the loading areas also to mechanical damage. The silver metallic paint,

however, shows no signs of corrosion damage, even at critical points such as punching holes, bolt and

screw connections or drip rails. The high performance level of chromium-free pretreated, coil-coated

aluminium plates for building applications has thus been demonstrated most impressively.

The chromium-free

pretreated trapezoidal

panels show unbroken

drip rails, even after 10

years of weathering.

Sun protection venetian

blinds made from coil-

coated panels

6.1.4.3 Chromium-free pretreated roof and wall cladding

For over 10 years, Novelis has been supplying chromium-free pretreated aluminium for roof and

façade elements from its factory in Bresso, Italy. In the Göttingen plant, the pretreatment is applied in

the no-rinse process. Since 2005, a few product groups with chromium-free pretreatment have been

manufactured here, and the percentage of such products has gradually expanded. Both plants use

alloys of the 1000, 3000 and 5000 series. The roof and façade elements usually have a 2-layer

construction with a chromium-free pretreatment and a chromate-free primer.

63

The two images show an office building with a coil-coated façade, built in 2002 in Darmstadt, and a

residential building with roof panels made from painted aluminium, built several years ago in Austria.

Both buildings continue to have a flawless appearance today. Both materials have undergone

extensive testing, in accordance with their future use, and specifically manufactured with chromium-

free pretreatment. Compared to the old pretreatment containing chromium, no deterioration could be

detected in these applications, even after several years.

 

 

Image: For the façade of this office

building in Darmstadt (Germany), which

was built in 2002, chromium-free

precoated aluminium elements were used

 

Image: The roof of this residence is made from

chromium-free pretreated roof elements

6.1.5 Summary

Chromium-free pretreated and, if necessary, primed coil-coated aluminium has been on the market for

more than 10 years and is accepted by customers. The weathering results show that the use of

chromium-free pretreatments in no way leads to inferior results. In some cases, they were even

marginally better, because during the conversion optimised primer or base coats could be used.

The conversion of the topcoat to chromate-free systems will occur after the REACH-prescribed cut-off

date for the use of lead chromates at the end 2013. Replacements are already partially available on

the market. For some critical colours, like bright orange or red shades, solutions are currently being

developed.

64

A model for the adaptation to the environmental and technical conditions is Deutsche Post: As early as

the 1980s, it deliberately changed the yellow colour to permit the use of lead chromate-free

pigmentation. An important external sign of its corporate identity was thus made more environmentally

friendly and material-conscious.

In addition to the construction industry, there are also markets, for example in aircraft construction,

where there are currently no alternatives to the use of chromate-containing coil coating. Here, partially

for safety reasons, chromate-containing systems continue to be used.

65

7 Preanodisation

Another environmentally friendly alternative passivation of the aluminium surface is the generation of

thin aluminium oxide layers, referred to as preanodisation.

Preanodisation has been successfully used in the construction industry for several years. It is applied

especially with locations of buildings near the coast, in aggressive industrial climates or application

areas particularly susceptible to filiform corrosion, such as swimming pools.

Earlier studies initiated by GSB International have shown that filiform corrosion can only be prevented

with a preanodisation beyond the required warranty periods. This has in fact been confirmed in

outdoor weathering studies by the Forschungsgesellschaft für Pigmente und Lacke e. V. (FPL)

(Research Institute for Pigments and Paints), of Stuttgart, as well as by the Forschungsinstitut für

Edelmetalle und Metallchemie (FEM) (Research Institute for Precious Metals and Metallochemistry), of

Schwäbisch Gmünd.

Since 1995, the preanodisation layer, produced under defined conditions, has been certified by GSB

International as a pretreatment process for aluminium. It should be implemented in accordance with

the provisions of section 8.3 of the quality guidelines GSB AL 631.

Anodic oxide layers can be produced only on a metal connected as the anode, which is immersed in

an electrolyte. By the action of the electric current generated during the electrolysis at the anode,

atomic oxygen is liberated, which reacts with the aluminium, forming alumina. This is solidly anchored

to the metal surface. The layers consist of an impermeable barrier layer and a porous outer layer, the

achievable thickness and pore diameter of which depend on the current density, time, temperature

and acid concentration. The pore density is about one billion pores per mm2 of external surface.

To prepare the adhesive artificial oxide layer, sulphuric acid is generally used as the electrolyte. The

layer thickness can be adjusted via the process parameters of temperature, current density and time.

Highly suitable layer thicknesses have been found to range between 5 and 8 μm.

The following are considered to be the properties of the layer and the process:

Very good corrosion resistance

Variable adjustment of layer thicknesses

Special plant technology is required

Only achievable with dipping

66

The anodic oxidation of aluminium, both in terms of the quality of the passive layers formed, and also

their technical importance, has a leading position in the surface pretreatment of aluminium. The very

good corrosion resistance, even under difficult operating conditions, and the good environmental

compatibility, are factors that favour the increasing use of these intermediate layers. The application of

preanodisation is a prerequisite for the awarding of the GSB International quality label "Sea Proof

Plus"

67

8 Summary

Image: Requirements for chromate-containing and chromium-free surface pretreatments

Since its introduction 50 years ago, chromating has grown steadily into a safe process for the

pretreatment of aluminium. Only through this safe process technology could electrostatic powder

coating develop to include coloured forming of aluminium in the construction industry in the last

forty years, in addition to proven electrochemical oxidation.

In particular, the high process safety and high corrosion protection achieved are very highly prized

in the market.

The classification of chromium (VI) compounds as compounds with carcinogenic and mutagenic

potential has been known for many years. Therefore, their inclusion in the candidate list (SVHC

list) comes as no surprise to the affected industries.

The use of chromating for the pretreatment of aluminium, however, continues to be legally

permitted until a final decision by the European Commission is reached.

The relevant national building codes and rules, such as the REACH Regulation, also do not rule

out the application of this surface pretreatment process at the current time.

There is no absolute clarity regarding how chromium (III) compounds will be classified in the

future. This also includes green chromating, which still possesses a certification for coatings that

come into contact with food products. However, the production of process chemicals always starts

from the basis of chromium (VI) compounds.

68

It is important to note that it is already a requirement of some individual cities and districts that a

chromium-free pretreatment be enforced for the use of aluminium in public buildings. This raises

the question of what is actually to be understood by the term "chromium-free". This requirement is

not consistent with the national building codes and the REACH chemicals ordinance, and

represents a tightening of the requirements profile. Harmonisation and an unambiguous

interpretation would be in the interest of all parties involved.

Since 1994, chromium-free pretreatment processes have been certified for the coating of

aluminium according to GSB International guidelines QR AL 631. The market now has a wide

range of available choices of definitively certified processes.

Several million square metres of coated aluminium with chromium-free pretreatment are the hard

evidence of the process safety of this pretreatment process.

The chromium-free process used must be adapted to the production parameters of the respective

plants; and also vice versa.

A systematic and continuous bath monitoring of the chromium-free pretreatment is required.

According to the current state of the art, this is more challenging than in the case of chromating.

The health protection of employees is much more thoroughly guaranteed with the use of

chromium-free pretreatment processes.

The increased durability of chromium-free processes compared to chromating is an important

economic factor.

Preanodisation is the chromium-free process that offers the best corrosion protection and the

highest resistance to filiform corrosion. This chromium-free process has been used successfully

more than 20 years in regions with particularly aggressive climates.

According to the present results, chromium-free pretreatment processes are classified as being

comparable in their corrosion protection to chromating processes. There are studies that have

confirmed the higher filiform resistance of chromium-free processes compared to chromium-

containing processes.

Also in other industrial sectors, chromium-free pretreatment has now established itself. Chromium-

free pretreatment, despite the existing objections, results in increased sustainable protection of the

environment and humans.

69

Acknowledgments

We would like to thank the fem, Forschungsinstitut Edelmetalle & Metallchemie, Schwäbisch Gmünd,

and all participating companies for their support, discussions, contributions and constructive co-

operation in the implementation of this document.

Legal notice: © GSB International 2012. Reprinting and photomechanical reproduction, even of individual pages of this work, is prohibited without permission. Translation of the 2nd, revised issue 2012. All rights, including translation into other languages, are reserved by GSB International. All statements, information and recommendations are based upon the information available at print time of printing and are provided without warranty or assumption of liability. Published by: GSB International e. V. Am Bonneshof 5 D-40474 Düsseldorf Tel.: +49 (0) 211 / 4796-450 Fax: +49 (0) 211 / 4796-410 E-mail: info@gsb-international.de Internet: www.gsb-international.de General processing: Hans-Jürgen Alfort, Dr. Axel Blecher, Werner Mader Title image: Hyatt Regency, Ekaterinburg, Russia (TK-Oberfläche, D-Bielefeld)