Hydrogen-assisted stress corrosion cracking

HSCC - Hydrogen- assisted stress-corrosion cracking. 

Hydrogen embrittlement, 428 Hydrogen production increase (catalyst poisoning), 164-165 Hydrogen sulfide, 90,106,111—112, 116, 133, 144, 173, 421-422 Hydrogen-assisted stress corrosion cracking, 90... 

To a lesser extent, the above warning applies to all amine systems. The presence of carboxylic acids produced from heat-stable salts, overloaded amine, and cyanides accelerates the process of hydrogen-assisted stress-corrosion cracking. 

Often massive corrosion failures occur suddenly, without the warning of any small leaks. Lines part at welds, vessels burst apart as a result of hydrogen-assisted stress corrosion cracking, and thin elbows peel back like the top of a soup can. Process plants are dangerous places, mainly because of corrosion hence the importance of monitoring corrosion. It is the responsibility of the imit chemical or process engineers to monitor corrosion on their units. 

Figure 46.2 Hydrogen-assisted stress corrosion crack causes vessel to fail.

Of course, the cracked weld was not a result of corrosion that day, or that week, or that month. The crack was a result of hydrogen activity and pressure accumulation inside the vessel wall for the past decade. It was a result of 10 years of proton penetration of the vessel wall. However, the final effect appeared suddenly. That s the nature of hydrogen-assisted stress corrosion cracking. 

The above simple concepts need to be modified and expanded to allow discussion of stress-corrosion cracking of stainless steels in general, especially as the role of hydrogen in assisting crack growth must be accounted for. 

Wei, R. P., Klier, K., Simmons, G. W., and Chou, Y. T., Fracture Mechanics and Surface Chemistry Investigations of Environment-Assisted Crack Growth, in Hydrogen Embrittlement and Stress Corrosion Cracking, Ronald Gibala, et al., eds., American Society for Metals, Metals Park, OH (1984), 103. 

Titanium is mainly susceptible to two types of localized attack - crevice corrosion and environment-assisted cracking (stress-corrosion cracking and/or hydrogen embrittlement). Titanium is resistant to pitting cor-... 

Severe loss of ductility of a metal (or alloy) loss of load carrying capacity of a metal or alloy the severe loss of ductility or toughness or both, of a material, usually a metal or alloy. Many forms of embrittlement can lead to brittle fracture and many can occur during thermal treatment or elevated-temperature service (thermally induced embrittlement). Some of these forms of embrittlement, which affect steels, include blue brittleness, 885 °F (475 °C) embrittlement, quench-age embrittlement, sigma-phase embrittlement, strain-age embrittlement, temper embrittlement, tempered martensite embrittlement, and thermal embrittlement. In addition, steels and other metals and alloys can be embrittled by environmental conditions (environmentally assisted embrittlement). Forms of environmental embrittlement include acid embrittlement, caustic embrittlement, corrosion embrittlement, creep-rupture embrittlement, hydrogen embrittlement, bquid metal embrittlement, neutron embrittlement, solder embrittlement, sobd metal embrittlement, and stress-corrosion cracking. 

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