Hydrogen Embrittlement | Materials And Corrosion Control
Damage Mechanism |
Hydrogen Embrittlement |
Damage Description |
A loss in ductility of high strength steels due to the penetration of atomic hydrogen, leading to brittle cracking. |
Affected Materials |
Carbon steel and low alloy steels, 400 Series stainless steels, Precipitation Hardenable (PH) stainless steels and some high strength nickel-based alloys. |
Control Methodology |
· The effect starts at temperatures from ambient to about 300°F (149°C). Effects decrease with increasing temperature and hydrogen embrittlement is not likely to occur above 160F to180°F (71°C to 82°C).
· This damage is dependent on the source of the hydrogen, alloy composition and fabrication/heat treatment history. · Use lower strength steels and Post-Weld Heat Treatment to temper the microstructure, improve ductility and reduce residual stresses and hardness. · Heavy wall equipment in hot hydrogen service requires controlled shutdown and start-up procedures to control the pressurization sequence as a function of temperature. · In corrosive aqueous services, apply a protective lining, stainless steel cladding or weld overlay to prevent the surface hydrogen reactions. |
Monitoring Techniques |
For surface cracking inspection use Penetrant Testing, Magnetic Particle Testing, Wet Fluorescent Magnetic Particle Testing and Ultrasonic Testing. |
Inspection Frequency |
Most inspections are performed visually and followed by Penetrant Testing or Wet Fluorescent Magnetic Particle Testing on several-year intervals. |
KPIs |
Strictly follow & document start-up & shutdowns, to observe recommended cooling/heating rates. |
Reference Resources (Standards/GIs/BPs) |
· API RP 571 |
High Temperature Hydrogen Attack (HTHA) | Materials And Corrosion Control
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