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Hydrogen Induced Corrosion

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Welding: Welding rod storage & Heat treatment ... Hot metal during processing... Hydrogen is able to diffuse out as the solubility decreases ... – PowerPoint PPT presentation

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Title: Hydrogen Induced Corrosion


1
Hydrogen Induced Corrosion
March 22nd, 2001 Matthew Avery Benjamin Chui Y.
Gordon Kariya Kenneth Larson
2
Outline
  • Mechanisms
  • Hydrogen Embrittlement
  • Hydrogen Induced Blistering
  • Precipitation of Internal Hydrogen
  • Hydrogen Attack
  • Cracking from Hydride Formation
  • Prevention
  • Case Studies
  • Questions

3
Hydrogen Embrittlement
  • Hydrogen in steel reduces the tensile ductility
    causes premature failure under static loads.
  • Only a few parts per million of hydrogen is
    necessary to embrittle steel.
  • Three primary theories
  • Decohesion Theory
  • Reduced Surface Theory
  • Planar Pressure Theory

4
Hydrogen Embrittlement
  • Basic Mechanism

s
Crack Tip
H2(gas)
s
5
Hydrogen Embrittlement
  • Basic Mechanism

s
H2(gas)
Dissociative Chemical Adsorption
Physical Adsorption
s
6
Hydrogen Embrittlement
  • Basic Mechanism

s
H2(gas)
Hydrogen Diffusion
s
7
Hydrogen Embrittlement
  • Decohesion Theory

s
s
smax
H2(gas)
x
s
8
Hydrogen Embrittlement
  • Reduced Surface Theory
  • The absorption of hydrogen decreases the surface
    free energy of the metal
  • Propagation of the crack tip is enhanced
  • Explains crack propagation of high-strength
    steels in low-pressure hydrogen environments

9
Hydrogen Embrittlement
  • Planar Pressure Theory
  • Occurs when metals are charged with hydrogen
    during solidification
  • High-pressure hydrogen can form in microvoids
  • Same mechanism as hydrogen blistering

10
Hydrogen Embrittlement
  • Crack Direction

11
Hydrogen Embrittlement
  • General Trends
  • Tendency to embrittle increases with decreased
    strain rate
  • Embrittlement is more prevalent at room
    temperature
  • Tendency to embrittle decreases with increasing
    temperature

12
Hydrogen Embrittlement
  • Prevention in Design
  • High-strength metals and alloys are more
    susceptible to embrittlement
  • Common mistake is to overcompensate on strength
    requirements for service
  • At ambient conditions
  • Minimize strength of material!

13
Hydrogen Embrittlement
  • Prevention in Processing
  • Embrittlement can originate from poor production
    techniques
  • Problems arise when hydrogen is allowed into
    production environment
  • Remedies
  • Maintain low hydrogen atmosphere
  • Heat treatment

14
Hydrogen Embrittlement
  • Prevention in Welding
  • Embrittlement can be localized around a weld
  • Welding rods containing hydrogen are the source
  • Remedies
  • Low hydrogen welding rods stored in a dry place
  • Local heat treatment before after welding

15
Hydrogen Embrittlement
  • Prevention
  • Design Minimize strength of material
  • Production Minimize hydrogen sources in
    production area Heat treatment
  • Welding Welding rod storage Heat treatment
  • Reversal Baking 100-650C under vacuum
    conditions can rid a metals of hydrogen
    inclusions

16
Hydrogen Embrittlement
  • Case Study
  • Unalloyed steel
  • High pressure boiler
  • Evaporator tube
  • Time to failure over 10 years
  • Environment flue gas deposits with sulphuric
    acid compounds
  • Remedy Use low-alloyed (hydrogen-resistant) steel

17
Hydrogen Embrittlement
  • Case Study
  • Steel Fastener
  • Multiple fracture origins
  • Subsurface cracking at inclusions

18
Hydrogen Induced Blistering
  • Hydrogen is absorbed into metal, diffuses inward,
    and precipitates as molecular hydrogen
  • Precipitates as laminations, inclusions, matrix
    interfaces
  • When cracks are just below surface, the exterior
    layer of metal will bulge
  • Enough pressure builds to produce internal cracks

19
Hydrogen Induced Blistering
  • Basic Mechanism

Physical Adsorption
20
Hydrogen Induced Blistering
  • Basic Mechanism

H2(gas)
Dissociative Chemical Adsorption
21
Hydrogen Induced Blistering
  • Basic Mechanism

H2(gas)
Hydrogen Diffusion
22
Hydrogen Induced Blistering
  • Basic Mechanism

H2(gas)
Blister Formation
23
Hydrogen Induced Blistering
  • General Notes
  • Hydrogen induced blistering can be seen as a
    special case of hydrogen embrittlement
  • Blistering most prevalent in low-strength alloys
    or metals that have been exposed to
    hydrogen-charging conditions

24
Hydrogen Induced Blistering
  • Prevention
  • Surface phenomenon
  • Source Hydrogen absorbed from the environment
  • Minimized hydrogen at surface
  • Corrosion inhibitors
  • Avoid cathodic protection and galvanic couples

25
Hydrogen Induced Blistering
  • Case Study
  • Unalloyed steel wall
  • Carbon dioxide scrubbing tower
  • Time to failure many years
  • Environment water and CO2
  • Use a non-corrosive scrubbing liquid,
  • Accept corrosion monitor its progress

26
Precipitation of Internal Hydrogen
  • Processing
  • Introduces 5-8 ppm
  • RT equilibrium at 0.1 ppm
  • Diatomic precipitation
  • Occurs at existing inclusions
  • Pressure causes enlargement of cracks
  • Cracks Embrittlement

27
Precipitation of Internal Hydrogen
  • Transgranular Cleavage

28
Precipitation of Internal Hydrogen
  • How hydrogen gets there
  • Atmospheric moisture
  • Impurities
  • Welding
  • Atmosphere
  • Surface contaminants
  • Welding rod

29
Precipitation of Internal Hydrogen
  • Fracture
  • Reduced ductility
  • Fracture initiation
  • inclusions
  • pores
  • Fracture surface
  • Fisheyes
  • Flakes
  • Typical of heavy steel forgings
  • Caused by internal residual hydrogen
  • Hairline cracks in center of part
  • Below 200 degrees C

30
Precipitation of Internal Hydrogen
  • Prevention
  • Internal phenomenon
  • Source Hydrogen absorbed during processing
  • Improved processing techniques with added heat
    treatment under vacuum

31
Precipitation of Internal Hydrogen
  • Prevention in Processing
  • Hydrogen solubility in iron
  • Low in ?-iron (low T)
  • High in ?-iron (high T)
  • Diffusivity increases with temperature
  • Result Quenching metals aids hydrogen corrosion
  • Low diffusivity traps hydrogen in metal
  • Hydrogen precipitates internally

32
Precipitation of Internal Hydrogen
  • Hot metal during processing…
  • Hydrogen diffuses in at high temperatures
  • Cool the metal …..

Hydrogen is trapped!
33
Precipitation of Internal Hydrogen
  • Hot metal during processing…
  • Longer annealing time under vacuum conditions…
  • Hydrogen is able to diffuse out as the
    solubility decreases

34
Precipitation of Internal Hydrogen
  • Case study
  • Viton B (rubber)
  • Environment oil well workover fluids
  • Time to failure months
  • Failure due to pressure buildup at voids in the
    material
  • The interiors of the blisters are similar to that
    of hydrogen flakes in steel

35
Hydrogen Attack
  • Mechanism
  • Environment
  • High P, high T hydrogen environment
  • Petrochemical plants
  • Hydrocarbon processing at 21 MPa, 540C
  • Stress level, exposure time, steel composition
  • Mechanism
  • Hydrogen reacts with carbides to form methane
  • Methane bubbles form at grain boundaries
  • Bubbles merge to create fissures

36
Hydrogen Attack
37
Hydrogen Attack
38
Hydrogen Attack
39
Hydrogen Attack
40
Hydrogen Attack
  • Characteristics
  • Symptoms
  • Unexpected failure
  • Microstructure
  • Decarburization along grain boundaries
  • Fissuring along grain boundaries
  • Embedded methane bubbles

41
Hydrogen Attack
  • Rapid cooling can cause
  • Hydrogen embrittlement
  • Blistering

42
Hydrogen Attack
  • Prevention
  • High temperature phenomenon
  • Petroleum processing reaches up to 540 C
  • Reaction with carbon
  • Methane and decarburized structures formed
  • Minimize carbon content for high temperature
    operation!

43
Hydrogen Attack
  • Case Study
  • Hydrogen attack at the ID weld in a high pressure
    carbon steel boiler tube

44
Hydrogen Attack
  • Case Study
  • Cracking due to hydrogen attack at the ID weld in
    a high pressure carbon steel boiler tube

45
Hydrogen Attack
  • Case Study
  • Carbon steel cooler pipe from heat exchanger
  • Time to Failure Several years.
  • Environment high internal pressure, gas mixture
    of hydrogen, nitrogen and ammonia at approx.
    240C.
  • Remedy Use 0.5 Mo steel or one of the Cr Mo
    steels

46
Hydride Formation Cracking
  • Affects Ti, Ta, Zr, U, Th
  • Hydrogen picked up during processing
  • Melting
  • Welding
  • Hydride formation upon cooling

47
Hydride Formation Cracking
  • Characteristics
  • Lower density than metal matrix
  • Increases strength
  • Decreases ductility, toughness
  • Platelets
  • Preferred orientation in lattice
  • Applied stress can cause hydride alignment

48
Hydride Formation Cracking
  • Hydrides in Titanium
  • Passivating at 100 C
  • Slow diffusion
  • 0.4 mm layer of TiH2
  • Spalling
  • Rapid formation above 250 C
  • Low hydrogen solubility
  • No spalling
  • Formation of hydride particles throughout
  • High susceptibility to failure
  • Typically occurs upon cooling from higher T

49
Hydride Formation Cracking
  • Passivation

Ti
50
Hydride Formation Cracking
  • Passivation

Ti
51
Hydride Formation Cracking
  • Passivation

Ti
52
Hydride Formation Cracking
  • Passivation

Ti
53
Hydride Formation Cracking
  • Prevention
  • Internal phenomenon
  • Results from high-temperature reactions between
    hydrogen and the metal
  • Remedies
  • Minimize operating temperatures
  • Heat treatment

54
Prevention Review
  • Design Specifications
  • Minimize material strength
  • Minimize carbon content for high-temperature
    operation
  • Avoid titanium for high-temperature operation
  • Minimize Hydrogen Content
  • Heat treatment (processing welding)
  • Use corrosion inhibitors
  • Maintain dry environment (storage)

55
Hydride Formation Cracking
  • Case Study
  • Titanium pipe
  • Used in Ammonium carbonate condenser.
  • Time to failure 5 years
  • Temp. 130C
  • Remedies reduce operating temperature, use
    stainless steel

56
Questions?!
applause please
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57
Have a Great SPRING BREAK!!!!!!
Have a Great SPRING BREAK!!!!!!
Have a Great SPRING BREAK!!!!!!
Have a Great SPRING BREAK!!!!!!
Have a Great SPRING BREAK!!!!!!
Have a Great SPRING BREAK!!!!!!
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