ON THE INITIATION AND GROWTH BEHAVIOR OF CORROSION PITS DURING CORROSION FATIGUE PROCESS OF INDUSTRIAL PURE ALUMINUM

It is well known that the fatigue limit in air disappears in a corrosive environment. This is often because corrosion pits initiate and grow in the early stage of corrosion fatigue process, and a final failure of specimen is brought by crack initiation and propagation from the grown pits, even if the applied stress amplitudes are small. Therefore, it is important to study the initiation and growth characteristics of corrosion pits in order to predict the corrosion fatigue lives of machines and structures that operate in corrosive environments. In this study we carry out corrosion fatigue experiments with an industrial-grade pure aluminum and two different types of corrosion methods. The initiation and growth characteristic of the corrosion pits were investigated by successive observations during the corrosion fatigue process using a replica technique. It was found that effect of stress amplitude differed depending on the corrosion method. It was also found that the growth characteristics of corrosion pits could be estimated quantitatively by changes in time of both the corrosion current density and the corrosion pit density.