Influence of the alloying elements on crevice corrosion of stainless steels: a modeling approach

摘要

Crevice corrosion chemistry is modeled in galvanostatic mode using finite el-ement method calculations. The results lead to the formulation of critical conditions for crevice propagation in terms of applied current and depassivation pH_d. For a given stainless steel grade, the model predicts a linear relation I_C(pH_d) between a "critical propagation current" l_C and the depassivation pH_d. Detailed computing is performed to compare the behavior of duplex 2304, ferritic AISI 430 and austenitic AISI 304 stainless steels. The model is shown to capture correctly the major asymptotic behaviors and to fairly predict the better corrosion resistance of the duplex grade, which is attributed to its slower dissolution kinetics in acidic environment. When comparing duplex stainless steels to ferritic or austenitic ones, it is now evident that the dissolution law and the depassivation pH_d are the key factors that control the resistance to crevice corrosion propagation.