Effect of the oxidizing power of the medium on intergranular corrosion of AISI 310 SS: influence of diffusion

Abstract

This paper deals with the influence of the oxidizing power of the medium on the intergranular corrosion (IGC) behavior of a non sensitized stainless steel (SS). Previous work has shown that in a moderately oxidizing medium (i.e. with a redox potential high enough to polarize the SS in its transpassive region which induces IGC), the SS has a typical behavior consisting of: a mass loss kinetics with a first parabolic part followed by a linear part and an evolution of the IGC morphology where the IGC grooves maintain a constant angle over time. In the present study, it is shown that this typical behavior changes significantly when the oxidizing medium becomes stronger (i.e. with an even higher redox potential): the mass loss kinetics becomes quasi-linear and the IGC grooves angle varies over time. It is demonstrated that this results from a change of limiting step. The SS dissolution kinetics is reaction-controlled in a moderately oxidizing medium and becomes diffusion-controlled in a strongly oxidizing medium. These results allow a more precise control of corrosion or decontamination of steels in such oxidizing environments.