Crevice Corrosion of Type 316L Stainless Steel in Alkaline Chloride Solutions

Crevice corrosion on Type 316L (UNS S31603) stainless steel in alkaline chloride solutions was studied by galvanostatic polarization of an occluded specimen with a polytetrafluoro-ethylene (PTFE) crevice former. It is shown that it is possible for crevice corrosion to propagate in such solutions, even at pH > 13. Unusually high IR drops were observed due to corrosion product precipitation but could disappear under certain conditions of crevice geometry and polarization current. There is no obvious difference between the dissolution behavior at an active crevice corrosion site in an alkaline chloride solution and that in a neutral chloride solution. For practical crevice corrosion in alkaline chloride solutions, the achievable crevice corrosion current would be strongly affected by the reduced kinetics of oxygen reduction at high pH. For solutions with pH ≥ 13, natural aeration and 0.05 M chloride, the minimum propagation potential is about equal to the corrosion potential.