Transition Criteria - From a Pit to a Crack

A brief review of pitting, which is a localized corrosion process resulting from pitting and fatigue interaction has been conducted in this paper. The transition of a pit to a crack is a very important phenomenon occurring under PCF conditions. Various theories for transition of a pit to a crack were examined within the limits of present understanding and limitations of the models. The transition of a pit to a crack was also discussed for a variety of pit shapes utilizing the pit aspect ratios, defect size and linear elastic fracture mechanics, crack tip characterizing parameters such as Mode I stress intensity factor range. Pitting corrosion and fatigue interaction is presented in terms of a four-stage model hypothesized within electrochemical and mechanical components. Limited data are presented to support the hypotheses in this paper, which need to be validated with more data.