A PROBABILITY MODEL FOR THE GROWTH OF CORROSION PITS IN ALUMINUM-ALLOYS INDUCED BY CONSTITUENT PARTICLES

Localized corrosion in the form of pitting in certain classes of alumi num alloys, e.g. 2024-T3 and 7075-T6, is recognized as one of the degr adation mechanisms that affect the durability and integrity of structu res, and it is a concern for commercial transport and military aircraf t. Fitting has been shown to initiate at Constituent particles, which are either anodic or cathodic relative to the matrix, and involves com plex electrochemical processes. Furthermore, local interactions betwee n particles and the matrix enhance the rate of pit growth. Probabilist ic modeling for the growth of corrosion pits in aluminum alloys in aqu eous environments in presented. The focus of the growth process is spe cifically the role of clustered particles. The purpose of the effort i s to estimate the cumulative distribution function (cdf) for the size of corrosion pits at a given time for use in multi-site damage and cra ck growth analyses. The model incorporates the evolution of local dama ge at each particle and the corrosion pit growth involving interaction s with neighboring particles. Some of the key random variables include d are the size, density and location of both the anodic and cathodic p articles. Statistical estimates for the distribution functions of the underlying random variables are based on experimental observations. (C ) 1998 Elsevier Science Ltd.