STOCHASTIC APPROACH FOR PITTING CORROSION MODELING .1. THE CASE OF QUASI-HEMISPHERICAL PITS

The present paper is devoted to a first approach to a theoretical model for pitting corrosion, which applies to a process initiated at reacting inclusions in the metal yielding the development of quasi-hemispherical pits. The model describes the distribution of reacting inclusions, the pit birth, pit death, and pit growth processes, and steady pitting corrosion, so that the gap between stochastic and deterministic aspects of the entire pitting process is covered. The predictions of the theory are compared to experimental data resulting from 316SS specimens in a borate-phosphate buffer containing sodium chloride. The geometry of pits formed in this system satisfies the hypothesis of the theoretical model. In the present model we consider a stochastic approach for pit growth, and to our knowledge there is no attempt so far to introduce a stochastic description of the pit growth process. The proposed approach to pitting corrosion is determined by a critical condition which is related to a critical volume. The time required to attain the critical condition is given by a random variable, as well as the pit passivation which is given in terms of equivalent stochastic characteristics. © 1990, The Electrochemical Society, Inc. All rights reserved.