Slow strain rate tests (SSRT) were performed on a highpurity
0.02% C steel in ammonium carbonate ([NH4]2CO3)
solutions at 70°C as a function of applied electrochemical
potential. As in previous studies, a narrow critical potential
range for fatal cracking in the active-to-passive transition of
a rapidly developed polarization curve was observed. At
potentials slightly active to the critical potential range,
transgranular (TG) and intergranular (IG) fissuring were
observed. At potentials noble to the critical range, IG fissuring
was observed. Fatigue precracking had no effect on the
extent or rate of stress corrosion cracking (SCC), nor did
hydrogen embrittlement (HE). Results supported previous
theories that IGSCC of carbon steels is the result of a very
specific interaction between grain-boundary chemistry and
the micromechanics of near-boundary interactions.
