The Relevance of Accelerated Electrochemical Pitting Tests to the Long-Term Pitting and Crevice Corrosion Behavior of Stainless Steels in Marine Environments

TLDR

Critical breakdown potentials for iron‑chromium alloys and commercial stainless steels in 3.5 % NaCl were reported. The study correlated electrochemical breakdown potentials with long‑term marine exposure data, showing that crevice corrosion severity is linked to the nobility of the protection potential derived from cyclic anodic‑polarization curves. Pitting performance of iron‑chromium alloys over eight years matched electrochemical predictions, and chromium additions (12–28 %) markedly increased nobility and pitting resistance.

Abstract

Values of the critical breakdown potential, for a series of iron‐chromium binary alloys and some commercial stainless steels in aerated 3.5% sodium chloride are presented. The results are correlated with previously published data on the same materials after prolonged exposure to a marine environment. Exact correlations were obtained between the pitting performance of the iron/chromium alloys and that predicted from electrochemical tests over an exposure period of eight years. The highly beneficial influence of chromium additions on the pitting resistance of the steels is shown by the pronounced increase in the nobility of over the range 12–28% chromium. Analysis of corrosion data on commercial stainless steels after 4.25 years exposure to sea water has shown that the degree of crevice corrosion attack is directly related to the nobility of the "protection or repassivation" potential, as determined from cyclic anodic‐polarization curves.