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Potentinstatically controlled slow strain rate (~ ___ 3.3 • 10-6/sec) tensile tests were conducted on AISI 1018 mild steel in hot (92~ caustic solutions of 3.35M NaOH and 2.5M NaOH § 0.423M NafS in a chemically inert cell. Reduction of area was used as a measure of susceptibility to stress corrosion cracking (SCC). The presence of sulfide ions raised the active-passive transition potential to more noble values, and maximum susceptibility to SCC occurred at potentials near the active-passive transition in each environment. Cracking at these potentials was further confirmed by conducting tests on prefatigue cracked double cantilever beam specimens at a known stress intensity, and crack fractography was studied by scanning electron microscopy. Crack liquid pH measurements were obtained with pH indicator paper using a freezing technique. A hydrogen embrittlement mechanism of SCC was eliminated from consideration in both environments on thermodynamic grounds. All observations were reasonably consistent with a dissolution mechanism of SCC involving film rupture events.

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