We previously reported an increase in thrust ball bearing vibration and the formation of ridge marks on the raceway surface due to electrolytic corrosion. However, that was a macroscopic study of how such ridge marks were formed, and no observations were carried out to determine the changes that occurred to the initial pits after their formation. In the present study, one of the initially formed pits was examined, and changes in its width and depth were observed as the vibration increased during flow of the corrosion current. Both the width and depth of the pit were found to increase in proportion with the amplitude of vibration acceleration. Coalescence of adjacent ridge marks into a single larger one and subsequent splitting into two were also observed.