Marine Corrosion Studies: Cathodic Protection of 304 Stainless Steel and Copper Crevices in Salt Solutions

摘要

Cathodic polarization studies of deep crevices involving 304 stainless steel or copper in 0.6 M (3 1/2%) sodium chloride solution have shown that 2-3 mil crevices with a distance-to-crevice-opening ratio of 12,000:1 are polarized and that the pH of the solution within these crevices shifts to the alkaline region. Polarization and pH changes were observed even when starting with an acid bulk electrolyte having a pH typical of that found in active crevices involving stainless steel. The data have been plotted on partial Pourbaix diagrams and indicate that hydrogen discharge would be expected even at the deepest location in the narrow crevice. The polarization and shift in pH data indicate that cathodic protection would be effective in both preventing and stopping crevice corrosion of stainless steel. It appears that the distance to which cathodic protection may be effective in crevices could be well beyond the crevice geometry studied. (Author)