CONTROL 0F CORROSION ON UNDERWATER PILES

PRESENTED

BY:VIMLESH VERMA

130110054

CONTENTS

• INTRODUCTION• CORROSION MECHANISM OF STEEL IN SEA

WATER• ZONES OF CORROSION OF STEEL PILES• CORROSION MANAGEMENT• CORROSION PROTECTION METHODS• CONCLUSION• REFERENCES

INTRODUCTION

Corrosion is the destruction of metals and alloys by the chemical reaction with the environment or it may be regarded as the reverse process of extraction of metals from ore.

It is a natural process which converts a refined metal to a more stable form such as its oxide, hydroxide or sulfide.

Corrosion degrades the useful properties of metals such as durability, strength, appearance.

CORROSION MECHANISM OF STEEL IN SEA WATER

• On steel piling in seawater, the more chemically active surface areas (anodes) are metallically coupled through the piling itself to the less chemically active surface areas (cathodes) resulting flow of electricity and corrosion of anodic areas.

Sometimes these active local areas do not shift position end, therefore, the metal suffers localized attack and pitting occurs.

In general smaller the anode area relative to the cathode area, Pitting is deeper.

ZONES OF CORROSION OF STEEL PILES

• Atmospheric Zone

• Splash Zone

• Tidal Zone

• Submerged Zone

ATMOSPHERIC ZONE

• Depending upon time of wetness, temperature, pollutants, Atmospheric Corrosion is responsible for a large fraction of the total corrosion.

• Corrosion rate is least in this zone(without protection) < 0.1 mm/year.

• Paints and Coatings are used in protecting this section.

SPLASH ZONE:

• The Splash zone can be characterized by as an aerated sea water environment where exposed material are almost continually wet.

• Corrosion rate (without protection) 0.3 mm/year.

TIDAL ZONE:

• This zone is alternately submerged in seawater and exposed to Splash zone as the tide fluctuates.

• Corrosion rate (without protection) 0.1-0.3 mm/year.

SUBMERGED ZONE

• The submerged environment zone usually characterized by well aerated water combined with marine bio fouling organism of both the plant and animal variety.

• Corrosion rate (without protection) 0.1-0.2 mm/year.

CORROSION MANAGEMENT

It is divided into three major phases:

• Phase 1 of the program is planning stage of project.

• For the planning stage ,three main requirements strategy, budget and schedule needed to overcome the problem raised from corrosion of reinforcement

PHASE 2

• Phase 2 of the program involves physical assessment and actual remediation.

• Inspections for severity of corrosion are conducted in this phase to determine what strategy or methods are most suitable to be applied.

PHASE 3

• Phase 3 of the program mainly deals with future monitoring of the repaired structure.

• Systematically identifying and managing the existing resources can be done by implementing internal or external monitoring system using current technology.

CORROSION PROTECTION METHODS

• PROTECTIVE COATING

• CATHODIC PROTECTION

• APPLICATION OF FRP COMPOSITES

PROTECTIVE COATINGS

• Inorganic Zinc Silicates Primers

• High Build Epoxy Coatings

• Zinc Rich Epoxy Primers

• Aliphatic Polyurethane Topcoats

CATHODIC PROTECTION

• Cathodic protection (CP) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell.

• Sacrificial Anodes are fitted or bonded to the metal to be protected.

• The implementation is simple, all you need is an anode, a power supply and engineering talent.

APPLICATION OF FRP COMPOSITES

The poor durability of conventional corrosion repairs has led to increased interest for its replacement by fiber reinforced polymers.

Although dry conditions are favorable but availability of resins that can cure in water has made it possible.

Fiber reinforced polymers have long been used for the repair and retrofit of concrete structural elements.

Lightweight, high strength and resistance to chemicals.

FRP WRAPPING AROUND PILES

CONCLUSION

• Though there is no absolute way to eliminate all corrosion on underwater piles, there are some effective measures to control them.

• Cathodic protection is quit simple and protective coatings are used in vast and expensive structures.

• The FRP composites have many advantages viz. lightweight, posses high strength and chemical resistance and moreover have incomparable flexibility.

• Of the various ways of wrapping of FRP composites , transverse wrapping is found to be the easiest

REFERENCES

www.google.com www.wikipedia.comhttp://resource.npl.co.ukhttp://www.dot.ga.govhttps://www.researchgate.net

Thank you