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TitleCORROSION IN OIL&GAS
File Size4.0 MB
Total Pages108
Table of Contents
                            Slide 1
Slide 2
Slide 3
Slide 4
Typical E&P process conditions
Internal corrosion
Internal (process-side) damage mechanisms
Slide 8
Slide 9
Slide 10
H2S corrosion – metal loss
Wet H2S corrosion
Cracking in sour service
Sulphide stress cracking (SSC)
Protection against SSC
ISO 15156 SSC zones for carbon steel
SSC limits for selected CRAs
HIC / SWC / blistering
Avoiding HIC / SWC
ISO 15156 (NACE MR0175)
Designing for H2S service
Slide 22
CO2 - containing environments
Types of CO2 damage
CO2 corrosion in a production flowline
Factors in CO2 corrosion
Effect of sand on CO2 corrosion
Mitigation of CO2 corrosion
CO2 corrosion inhibition
CO2 + H2S corrosion – metal loss
H2S + CO2 materials selection guide
Slide 32
Flow regimes
Erosion & erosion-corrosion
Typical vulnerable areas for erosion
Erosion in piping
Erosion in a vessel
Erosion of sandwash nozzle
Erosion-corrosion
Impingement
Cavitation
Slide 42
Raw seawater
Pitting resistance of stainless steels
Internal & external pitting
Failure of a seawater pump cooling coil……
Oxygen - concentration cells
Galvanic corrosion
Galvanic corrosion – firewater piping
Galvanic corrosion - seal rings
Dealloying of brass
Mitigation of galvanic corrosion
Slide 53
Cathodic protection (CP) – what is it?
Cathodic protection – how does it work?
Galvanic (sacrificial) CP
Applications of internal CP
Chloride stress corrosion cracking (SCC)
Chloride SCC (22Cr duplex vessel drain)
Water injection systems (deaerated)
Mitigation & monitoring
Preferential weld corrosion (PWC)
Preferential weld corrosion (1%Ni)
Lomond drains - PWC
Slide 65
Microbially induced corrosion (MIC)
Bacterial growth factors
Deadlegs – types & locations
Examples of deadlegs
Deadlegs – assessment factors
Example of deadleg corrosion
Root causes
Mitigation & inspection
Slide 74
Corrosion due to chemicals
Slide 76
Injection point issues
High temperature corrosion
Amine stress corrosion cracking
Corrosion in glycol system
Corrosion fatigue
Example of corrosion fatigue
Slide 83
External corrosion
Where does it occur?
What does it look like?
Appearance
Piping, supports & clamps
Not just carbon steel
Corrosion of bolts and fasteners
Slide 91
Flanged connections
Corroded fasteners (seawater service)
Structures / valves
Coating damage and breakdown
External cathodic protection
Impressed current CP
Corrosion under insulation (CUI) and Corrosion under fireproofing (CUF)
Insulation
CUI incident
CUI gas leak
piping CUI
CUI on pressure vessel
External pitting & crevice corrosion
Instrument tubing  (316 SS and super-duplex)
Crevice corrosion under clamps/supports
External chloride stress corrosion cracking
External stress corrosion cracking
                        
Document Text Contents
Page 1

CORROSION AND

ITS PROTECTION

IN OIL & GAS PRODUCTION

Page 2

CORROSION IN OIL FILED :
INTERNAL AND EXTERNAL THREATS

Page 54

54

Cathodic protection (CP) –
what is it?

• By connecting an external anode to the component to be
protected and passing a dc current, it becomes cathodic and
does not corrode.
– External anode may be a galvanic (sacrificial) anode, the

current is the result of the potential difference between the
two metals

– External anode may be an impressed current anode,
current is supplied from an external dc power source.

• CP is mostly applied to coated, immersed and buried structures
– The coating is the primary protection, acting as a barrier

between the metal and the environment
– CP protects steel at coating defects

• Coating + CP is most practical and economic protection system.
– Primary principle in GP 06-31

Page 55

55

Cathodic protection – how
does it work?

ANODIC

Magnesium
Zinc

Aluminium
Iron (steel)

Copper
Stainless steels

Titanium
Graphite

CATHODIC

Corrosion of
steel by copper

plating

Cathodic protection
of steel by zinc

plating

• CP works by making the component to be protected the cathode in an electrolytic cell

• When two metals are connected in an electrolyte, electrons flow from the anode to the
cathode due difference in the electrical potential

Page 107

107

External chloride stress
corrosion cracking

• Mechanism same as internal chloride SCC however:
• Numerous variables influence susceptibility therefore

guidance differs
– Material, stress, chlorides, oxygen and temperature
– No absolute guidance available, seek expert advice

Chloride SCC is
characterised by trans-

granular crack paths

Page 108

108

External stress corrosion
cracking

• UK HSE:
– Coat 22Cr duplex >80°C

• NORSOK M-001 SCC temp limits:
– 22Cr duplex >100°C
– 25Cr super-duplex >110°C

• Recent testing has shown failures at
80°C
– now recommend 70°C as limit

• Reliant on external coatings to act as
barrier (isolate from environment)

• Beware solar heating - can raise
external temperature above threshold
limits!
– SCC failure of 316L

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