Embrittlement, hydrogen induced corrosion

Hydrogen embrittlement, hydrogen-induced cracking, and hydrogen attack Nonmetallic Corrosion... 

Cracking mechanisms in which corrosion is implicated include stress corrosion cracking, corrosion fatigue, hydrogen-induced cracking and liquid metal embrittlement. Purely mechanical forms of cracking such as brittle failure are not considered here. 

The heart of corrosion science has been identified as electrochemical science coupled with the thermodynamic and kinetic values. Other limbs are oxidation and high-temperature oxidation of metals, protective coatings, passivity, inhibitors, microbial-induced corrosion, corrosion fatigue, hydrogen embrittlement and corrosion-resistant alloys. Having identified the limbs of corrosion science, it is instructive to examine how the various aspects came into existence over a period of time. 

Nelson, H.G. and Williams, D.P., Quantitative observations of hydrogen-induced, slow crack growth in a low alloy steel, in Stress Corrosion Cracking and Hydrogen Embrittlement of Iron Base Alloys, Staehle, R.W., Hochmann, J., McCright, R.D., and Slater, J.E., Eds., NACE, Houston, TX, 1977, pp. 390-404. 

Fig- 7.72 Schematic representation of stress induced surface profiles representative of the potential ranges identified in Fig. 7.71. (a) Hydrogen embrittlement, (b) Active corrosion, (c) Passive film cracking, (d) Passivity, (e) Pit-initiated cracking... 

A primary agent causing most stainless steel SCC failures is the chloride ion. The stainless steels that are most susceptible to this form of corrosion are the approximately 8-10 % nickel austenitic grades. However, as the nickel content of the austenitic steels increase beyond this level, the resistance to SCC increases. The ferritic stainless steels, with no nickel or copper, are resistant to this form of corrosion. However, ferritic grades are more prone to hydrogen-induced cracking or embrittlement. 

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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