Three-dimensional computational simulation of corrosion pit growth morphology

Pitting corrosion is one of the most significant degradation mechanisms that affect the integrity of a structure, and a great deal of useful information may be revealed by a study on corrosion pit growth morphology. To obtain the corrosion pit morphology as well as the aspect characteristics of an object subjected to a corrosive environment, a three-dimensional model is developed to simulate the evolution of pitting corrosion damage based on cellular automaton (CA) technology. The corrosion damage evolution process is simulated as a discrete dynamical system, and the following elementary physicochemical processes are taken into account in the proposed model: mass transport, IR drop, metal dissolution and repassivasion, which are described by a number of local rules. The pitting corrosion morphology at different corrosive environments is obtained by implementing the simulation procedure. The pit depth ratio, which is defined as the ratio of the equivalent pit depth to the simulated pit depth, is introduced to characterize the tendency of a pit to a semi-ellipsoid; and the pit aspect ratio is used to study the equivalent pit morphology characteristic for the corrosion pit considered as the semi-ellipsoid. The results show that pit growth can achieve a relative steady state during the pitting corrosion process. These preliminary investigation results will motivate further work to understand the pitting corrosion mechanism, and provide valuable information for fatigue life prediction and structural integrity analysis.