116 Environmentassisted Failure

In many instances corrosion problems are exacerbated by synergistic effects caused by the joint action of mechanical stress and chemical reactions. There are three major processes by which the integrity of a component may be affected: (i) stress corrosion cracking (SCC), (ii) corrosion fatigue (CF), and (iii) hydrogen embrittlement (HE).

TABLE 11.4 Metal/Environment Systems Susceptible to SCC

Metal/Alloy Environment

Al alloy NaCl and H2O solutions, H2O vapor

Cu alloys Ammonia solutions and vapors, water, amines

Mg alloys NaCl, NaCl/K2Cr2O7 solutions

Steels NaOH, NaCl, and NO3 solutions; mixed acids; H2S gas/solutions

Stainless steels Acidic NaCl solutions at elevated temperatures, MgCl2, H2S

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