Initiation modeling of crevice corrosion in 316L stainless steels

Abstract

An advanced mathematical model has been developed to evaluate transport processes and chemical reactions during the initiation stage of crevice corrosion. The model considers the time evolution of the solution chemistry and electrochemistry within crevices, and uses the method of finite elements to solve the complex set of mass-conservation equations describing the system. In order to produce a useful estimate of the time of the incubation period, the concept of CCS (critical crevice solution), which delineates the transition between the passive and active states, has been introduced. The most important factors in crevice corrosion are the crevice gap and the crevice depth, especially the ratio of depth/width, on which the initiation of crevice corrosion reacts most sensitively. The potential drop inside the crevice consists of two components, the chemical potential drop and the physical potential drop, and the ratio of these components seems to be related to the crevice geometry. The results of numerical simulation of 316L (Fe–Cr–Ni–Mo alloy) show that the incubation time of the crevice corrosion is strongly dependent on the depth/width ratio of the crevice geometry.