Journal of the Electrochemical Society, Vol.140, No.12, 3425-3435, 1993
Distributions of Cr Depletion Levels in Sensitized Aisi304 Stainless-Steel and Its Implications Concerning Intergranular Corrosion Phenomena
An electrochemical method has been employed to obtain the population distribution of minimum grain boundary Cr concentrations for sensitized AISI 304 stainless steel (S30400). The detailed information about the extent of Cr depletion provided by the distribution is compared to the average degree of sensitization (DOS) evaluated by the standard and a modified single loop-electrochemical potentiokinetic reactivation (SL-EPR) technique. The distribution of Or levels on a grain by grain basis is shown to provide information about intergranular stress corrosion cracking (IGSCC) susceptibility that cannot be provided by EPR methods. Sensitized 304SS tested in an environment relevant to nuclear reactors has been shown to fail by IGSCC when the grain boundary Cr concentration is depleted to below a critical level of approximate to 13.5%. In a separate study, it has been shown that more than 23% of the grain boundaries must be depleted to the relevant critical level in order to observe macroscopically brittle behavior. The present study combines these two criteria and defines a sensitized material’s lGSCC susceptibility by revealing the extent of Cr depletion as well as the quantity of depleted grain boundaries.
Keywords:REACTIVATION METHOD;CHROMIUM DEPLETION;DETECTING SENSITIZATION;CRACKING;TYPE-304;AISI-304;MODEL;KINETICS;PREDICT;ALLOYS