Evolution of wetted and corroded areas on 8Cr4Mo4V bearing steel exposed to salt water contaminated lubricant oil

Relationship between wetted and corroded areas on 8Cr4Mo4V bearing steel during exposure to salt water contaminated lubricant oil was explored by Monte Carlo simulation and corrosion experiment. Results show that locally corroded areas are initially scattered then connected and eventually merged due to droplet coalescence, and are resulted from galvanic, uniform and filiform corrosions, respectively. Droplet coalescence also redistributes wetted areas and activates de-wetting which interrupts transformation towards corrosion. Role of droplet coalescence in evolution of corroded areas is addressed. Combining two Monte Carlo models varied with droplet relaxation helps to predict the corroded areas' distribution after long-term exposure.