Effects of mechanical stress on protective properties of a marine coating on mild steel substrate

The degradation behaviour of a marine epoxy coating on Q235 steel under mechanical stress in 3.5 % NaCl solution was investigated by electrochemical impedance spectroscopy (EIS) and adhesion tests. Results revealed that mechanical stress had a significant effect on coating barrier properties, adhesion, delaminated area, water uptake and diffusion, and this effect was not only related to the magnitude and direction of stress, but depended on immersion time. The coating under mechanical stress, regardless of stress direction, deteriorated faster than that under unstressed state. The disparity in changing trends of water uptake and diffusion coefficient with mechanical stress was also discussed.