Technical Note: On the Variability of Crevice Corrosion Initiation in Ferric Chloride Exposure Tests^*

In earlier papers, the initiation of crevice corrosion of austenitic stainless steels was characterized by a crevice corrosion temperature (CCT).^1,2  The CCT was defined as that temperature below which corrosion will not initiate at the most severe crevice geometry in a sample of stainless steel exposed to an oxidizing acid chloride environment such as 10% FeCl₃. The CCT was determined experimentally on a go/no-go basis by means of step-wise increases in temperature of 2.5 C at 24 hour intervals. At the end of each isothermal exposure period, the stainless steel coupon was examined visually for any corrosion attack (edge, end-grain, crevice, etc.). If no attack was observed, the coupon was exposed for a further 24 hours at a 2.5 C higher temperature. In this way, the CCT was bracketed by that 2.5 C interval in which the go/no-go characteristics were observed. For Mn-substituted austenitic stainless steels in...