The anodic behavior of a purified 16 Cr‐20 Ni stainless steel, which was unsusceptible to stress corrosion cracking, was compared with that of a susceptible 18 Cr‐8 Ni alloy in 42% MgCl 2 at 146°C. Potential‐time curves, potential‐current curves, and potentiostatic current‐time curves were compared. The potential‐time behavior of pure iron, chromium, and nickel was also determined and indicated that dissolution from a nickel‐rich surface controlled the anodic behavior of the stainless steels. Potentiostatic corrosion at potentials 50–100 mv more noble than the initial immersion potential eliminated the crack‐initiation period and increased the density of cracks by two orders of magnitude in the susceptible alloy. In the 16–20 alloy these potentials caused rapid corrosion and/or deep pitting but no cracking. Potentiostatic corrosion in this potential range provides a highly accelerated test for susceptibility to cracking. From potential‐current curves it was shown that propagation is accompanied by enhanced metal dissolution, in agreement with the general electrochemical mechanism of cracking.
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Barnartt et al. (1961) studied this question.