CHE 431 PowerPoint [Student]

8/15/2019 CHE 431 PowerPoint [Student]

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CORROSION OF

METALS AND ALLOYS

3 units

CHE 431Course Instructors: Dr. Ayoo! A.A.

Mr. O"un#iyi A.T.


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Mode of Assessment

Quiz = 5%

Test = 10%

Grp. Assig. = 15%

Cont. Ass. 30%

Exam. 70% Total 100%

06/05/16 COVENANT UNIVERSITY GEC 210 2


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MODULES

Introu!tion

"rin!iples o# Corrosion

$orms o# CorrosionCorrosion Testing

Corrosion Control & Anoi! '

Cat(oi! "rote!tion



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MODULES

Corrosion Control & )aterials

*ele!tion

Corrosion Control & "rote!ti+e

Coating an ,se o# In(iitors

-is!ussion on GroupAssignment



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GROUP ASSIGNMENT

G/," 1: Corrosion in Automobile Industries.

G/," : Corrosion in Chemical

Industries.

G/," 3: Corrosion in Petroleum

Industries.int2 Discussion should centre around the mode of

operations, nature and effects of corrosion, and

remedies in a parti!ular inustr&.



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MODULE ONE:

INTRODUCTION

Corrosion2 A atural "ro!ess

FI$%RE 1: T&e Corrosion Cyce o' Iron


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Two m!o" f#to"s of Co""os$on

)etal material an

An en+ironment.

• The corrosion #e&!(ior o' !)!teri! cannot be described unlessthe environment in which the materialis exposed to is i*enti+e* !n**e+ne*.

•T&e corrosi(ity or !""ressi(enesso' !n en(iron)ent cannot bedescribed unless the material that isto be exposed to that environment is

i*enti+e*.


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%&AT IS CORROSION'

Corrosion can be defned as achemical or electrochemical reaction

between a

material, usually a metal, and itsenvironment that produces

deteriorationand alteration o the material and its

properties.


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T(e m$n f#to"s )sed to des#"$*e

t(e en+$"onment "e:

• Physical state

• Chemical composition

•Temperature


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,ORMS O, CORROSION

•ni!orm or "eneral corrosion•Pittin# corrosion

•Cre$ice corrosion

•"al$anic corrosion

• %rosion corrosion

•&nter#ranular corrosion

•'ealloyin#

•%n$ironmentally assiste( crac)in#


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C-ss$f$#t$on of ,o"ms of Co""os$on


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,ACTORS IN,LUENCING METAL

CORROSION

1. NATURE O, T&E METAL


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,ACTORS IN,LUENCING METAL CORROSION

/Contd

2. NATURE O, ENVIRONMENT


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MODULE T%O:

PRINCIPLES O, CORROSION

T&EORIES O, CORROSION

1 'irect Chemical ttac) Theory

2 The %lectrochemical Theory


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CORROSION REACTIONS


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Co""os$on Re#t$on /Contd


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Co""os$on Re#t$ons /Contd


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Ct(ode Re#t$ons


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Co""os$on of met- s)"f#e


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Mes)"ement of Co""os$on Rte

O#,ecti(es o' Corrosion r!te


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Mes)"ement of Co""os$on Rte

-A /EI$HT 0 LOSS METHOD

- MICROSCO2IC

EAMINATION

-C MEAS%REMENT OFELECTRICAL RESISTANCE


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1. Un$fo"m Co""os$on: uni!orm thinnin# o$erthe entire sur!ace

MODULE T&REE:

,ORMS O, CORROSION


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2. P$tt$n4 Co""os$on:

characterise( y sharply (e!ine( holes


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C"e+$#e Co""os$on:

This is a !orm o! localie( attac) that occurs at narroopenin#s or spaces #aps eteen metaltometal or

nonmetaltometal components

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6. G-+n$# Co""os$on:occurs hen a metal or alloy is electrically couple( to

another metal or con(uctin# nonmetal in the same

electrolyte

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7. E"os$on Co""os$on:

&s the accelerate( or increase in the rate o! (eterioration

or attac) on a metal ecause o! mechanical ear or

arasi$e contriutions in comination ith corrosion

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8. Inte"4"n)-" Co""os$on:

selecti$e (issolution o! #rain oun(aries: or closelya(;acent re#ions: ithout appreciale attac) o! the

#rains themsel$es

&n a((ition to the presence o! impurity atoms:

metals contain many atom $acancies: that is: sites

here atoms shoul( e present ut are not

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9. De--o5$n4 Co""os$on:

is a corrosion process in hich the more acti$e metal isselecti$ely remo$e( !rom an alloy: lea$in# ehin( a

porous ea) (eposit o! the more acti$e nole metal

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ALLOY ENVIRONENT ELEENT REOVE!

"rasses#$inc %ater& especiall' sta(nant

water

$inc )de*inci+cation,

-ra' Iron .oils& water Iron )(raphic orrosion,

Aluminium bron*es /'dro0uoric acid& acids

containin( chloride ions

Aluminium )dealumini+cation,

.ilicon bron*es /i(h temperature steam and

acidic species

.ilicon )desiliconi+cation,

1opper nic2els /i(h heat 0ux and low water

velocit' )re+ner' condenser

tubes,

Nic2el )denic2eli+cation,

Tin bron*es /ot brine or steam Tin )destanni+cation,


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. St"ess Co""os$on C"#;$n4:

.tresses that causes crac)in# result !rom el(in#:hammerin#: thermal treatment or applie( loa(s (urin#

ser$ice &n such cases: the metal un(er stress ecomes

more ano(ic an( ten(s to increase the rate o!

corrosion

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MODULE ,OUR:

CORROSION TESTING

P)"oses of Co""os$on Test$n4

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Stes $n Co""os$on Test P"o4"m

1 'e!ine The Test -;ecti$es

2 &(enti!y the Time n( Cost/


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C-ss$f$#t$on of Co""os$on Test$n4

T(e"e "e t("ee 4ene"- #te4o"$es of

#o""os$on tests:

L*o"to"5 Tests

P$-ot -nt Tests

,$e-d Tests

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MODULE ,IVE: CORROSION

CONTROL


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Ct(od$# P"ote#t$on:

Catho(ic protection is achie$e(


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Ct(od$# P"ote#t$on

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Ct(od$# P"ote#t$on

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Anod$# P"ote#t$on

• achie$e( y maintainin# an acti$e > passi$e metal or

alloy in the passi$e re#ion y an e?ternally applie(

ano(ic current The potential o! the metal to e

protecte( is ma(e more positi$e to shi!t the

con(itions !rom a re#ion o! acti$e corrosion to are#ion o! passi$e eha$iour

• no(ic protection is use( to passi$ate stora#e tan)s

an( process $essels containin# hi#hly corrosi$e

electrolytes

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Anod$# P"ote#t$on

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@ Potential sensin# (e$ice: < @ Potential controller: C @ 'C poer source:

' @ ,e!erence %lectro(e: % @ Catho(e: A @ Tan) no(e

Ad f A d$ P $


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Ad+nt4es of Anod$# P"ote#t$on o+e"

Ct(od$# P"ote#t$on

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D$sd+nt4es of Anod$# P"ote#t$on

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MODULE SI= CORROSION


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MODULE SI=: CORROSION

CONTROL


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Mte"$-s Se-e#t$on

>A? Re@)$"ements To


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Mte"$-s Se-e#t$on

>


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Info"mt$on on Est$mt$n4 Co""os$on

Pe"fo"mn#e

>A? Co""odent V"$*-es%n$ironment type marine: in(ustrial: internal !lui(

etc

=ain constituents i(entity an( amount

Temperature

p

'e#ree o! aeration

Delocity or a#itation

Pressure

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I f t$ E t$ t$


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Info"mt$on on Est$mt$n4

Co""os$on Pe"fo"mn#e

>


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>C? T5e Of A-$#t$on

Ehat is the !unction o! part or e*uipmentF

re sie chan#e: appearance or corrosion pro(uct

prolemFEhat e!!ect ill localie( corrosion ha$e on use!ulnessF

Eill there e stresses presentF

&s (esi#n compatile ith the corrosion characteristics o!the materialsF

Ehat is the (esire( ser$ice li!eF

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>D? Ee"$en#e

as material een use( in an i(entical situationF

Ehat ere the resultsF

as material een use( in a similar situationF Ehat

as the per!ormanceF

Eas there any pilot e?perienceF

re there any plant corrosion test (ataFEhat literature or (ataase in!ormation is a$ailaleF

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%(t to #ons$de" *efo"e se-e#t$n4

mte"$-s

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Mte"$-s #ommon-5 )sed

Met--$# mte"$-s:>A? STAINLESS STEELS

=artensitic types

Aerritic types'uple? Aerriticustenitic types

Precipitationar(enin# types

ustentic types>


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Mte"$-s #ommon-5 )sed

on )etalli! materials2

[A] PLASICS

[!] C"#A$ICS[C] C%&C#""

[D] '%%D

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MODULE SEVEN CORROSION


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MODULE SEVEN: CORROSION

CONTROL


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COATING

Coatin#s an( linin# may protect

metals/alloys throu#h three asic

mechanisms+


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IN&I


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T5es of In($*$to"s

Commonly use( inhiitors are+

Anod$#

Ct(od$#O(m$#

P"e#$$tt$onVo)" (se

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A-$#t$on of In($*$to"s

&nhiitor application techni*ues inclu(e+

Cont$n)o)s $n!e#t$on


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CORROSION IN AUTOMO

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