Kinetics for pitting corrosion of a 13 Cr steel in neutral chloride solutions

Abstract

Abstract The kinetics of pitting corrosion is pre‐dominantly a function of the induction time and of the pitting potentials, so that it is indispensable to find all those two parameters. In order to find the potential one may use potentiostatic methods, the criterion of pitting corrosion being the current increase and the pit formation made visible in the stereomicroscope. The induction time increase as the applied potential decreases. The differences in the shape of the pits(spherical, semispherical, conical) have not been clearly interpreted so far; basically, in most cases, the cross section of the pits is semispherical at first, the radius increasing double the radius of the opening of the pit. From this moment on there is only pit growth to the depth, the pit becoming of conical shape. The overall mechanism is diffusion controlled, and the reduction of oxygen may play a certain role, too.