Corrosion Awareness - Atmospheric Corrosion Rev1

7/30/2019 Corrosion Awareness - Atmospheric Corrosion Rev1

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Copyright Talisman Energy (UK) Limited 2004

AN INTRODUCTION TO

ATMOSPHERIC EXTERNAL CORROSION

by


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INTRODUCTION

1. Corrosion Under Insulation

2. Atmospheric External Corrosion

3. Stress Corrosion Cracking and localised corrosion of stainless steels in chloride environments

4. Galvanic Corrosion

5. Flange Face Corrosion

6. Carbon Dioxide Corrosion

7. Hydrogen Sulphide Corrosion and Cracking

8. Oxygen Corrosion of seawater and water injection systems including internal corrosion of

stainless steels in chloride environments

9. Microbial Influenced Corrosion and Dead Leg Corrosion

10. Weld Corrosion

11. Erosion Corrosion

12. Fatigue and Fretting


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INTRODUCTION

External Atmospheric Corrosion

A form of oxygen corrosion. The threat is mainly to Carbon Steelbut some corrosion resistant alloys may also be at risk.

Corrosion is a risk wherever the surfaces of structural, process and

mechanical equipment are exposed to aerated water.

Not to be confused with Chloride Pitting and cracking of Corrosion

resistant alloys (covered in the next presentation)

This presentation briefly covers..

Where does it occur?

Locations and items where Atmospheric corrosion is likely to beseen

When does it occur?

When are you likely to see Atmospheric corrosion?

Why does it occur?

What has to happen for Atmospheric corrosion to become aproblem?

What can be done to prevent it?


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INTRODUCTION

POLICY Talisman seek to assure thecontinued integrity of all sites minimising risk to

personnel, environment and business from thethreat of Atmospheric Corrosion

STRATEGY Fabric maintenance programmes Risk based inspection schemes Planned maintenance routines Corrosion risk assessments

Coating conditions are reported using RI codes inACET and Metacor Fabric Maintenance database.


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WHERE DOES IT OCCUR?

Areas open to salt water sprayExposed areasDeluge areas

Items at riskVesselsPipework

Risers

Bolts/Flanges

Pipe supportsDeck plating

Stairs/ladders

Handrails

Mesh grating/cable trays


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Specific risks Areas atelevated temperatures

Pipework or vessels that operate

between 40o

C and 80o

C are at

high riskWet, hot surfaces

Areas adjacent to insulated

equipment


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Specific risks Areas of

trapped water (Crevices)

Pipework supports

Bolts/Flanges Fixings for nameplates

Supports for Stairs/ladders

Cable trays

Any area where water may pool

Underneath coatings Edges of

damaged coatings


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Specific risks Bolts & Flanges

Bolts and flanges form crevices

Coatings are often weaker

Galvanic corrosion if dissimilar materials

(presentation 4)



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Specific risks Uncleansurfaces

Build up of deposits on a surface

Salt deposits

Corrosion product

Fluid spills

Bird droppings

Residue/remains from tapes



WHEN DOES IT OCCUR?

When bare steel is exposed on asurface due to..

Coating degradation

Blisters

CrackingFlaking

De-bonding

Constant exposure to water

High traffic wear

Mechanical damage



WHEN DOES IT OCCUR?

When bare steel is exposed in a crevice by.. Ineffective seals on supports

Ineffective coating within the crevice

Poor design



WHY DOES IT OCCUR?

Why does the coating fail?Due to age

Due to poor application in field

Due to mechanical damage



WHY DOES IT OCCUR?

Why do deposits accumulate on surfaces?

Leaks/spills not cleaned up

Surfaces not kept free of debris

Corrosion product not removed



WHAT CAN BE DONE TO PREVENT IT?

Understand where and why the main

corrosion threats occur

Understand the systems in place toaddress these

Play your part Report any corrosion concernse.g. damage to coating, corrosion exposed when

carrying out routine tasks

Report any corrosion damage

e.g. Integrity Report cards, STOP cards, inform

Supervisor

Report any damage to coatings

Bolts ensure joints are assembled correctly

Clean up spills or debris



SUMMARY

Where does it occur?

Any areas exposed to water

When does it occur? When the surface is exposed

Why does it occur? Effective coating not maintained

What can be done to prevent it?

Effective fabric maintenance to preventextensive coating breakdown

Avoid leaks/spills onto surfaces from

above

Prevent accumulation of deposits/debris

Corrosion Awareness - Atmospheric Corrosion Rev1

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