Probability Modeling for the Growth of Corrosion Pits

Localized corrosion in the form of pitting in certain classes of aluminum alloys, e.g. 2024-T3 and 7075-T6, is recognized as one of the degradation mechanisms that affect the durability and integrity of structures, and it is a concern for commercial transport and military aircraft. Pitting has been shown to initiate at constituent particles, which are either anodic or cathodic relative to the matrix, and involves complex electrochemical processes. Furthermore, local interactions between particles and the matrix enhance the rate of pit growth. Probabilistic modeling for the growth of corrosion pits in aluminum alloys in aqueous environments is presented. The focus of the growth process is specifically the role of clustered particles. The purpose of the effort is to estimate the cumulative distribution function (cdf) for the size of corrosion pits at a given time for use in multi-site damage and crack growth analyses. The model incorporates the evolution of local damage at each particle and the corrosion pit growth involving interactions with neighboring particles. Some of the key random variables included are the size, density, and location of both the anodic and cathodie particles. Statistical estimates for the distribution functions of the underlying random variables are based on experimental observations.