Corrosion mechanism of arc spraying aluminum coatings in marine environment

Aluminum coatings were sprayed on Q235 steel by arc spraying. The failure process was studied through the simulated immersing tests in 3.5% NaCl solution at a fluid velocity of 0.6 m·s^-1 and a test temperature of 50 ±1℃. The results showed that there was little difference in the corrosion rates of undamaged and partially damaged samples. Uniform corrosion of the aluminum coatings was slight. Local corrosion occurred on the coatings because of synergism of the occluded cell and the active-passive cell. The main corrosion type was pit corrosion which induced bed separation and pits. Once corrosive solution arrived at the substrate, galvanic corrosion occurred, and aluminum coatings acted as the sacrificial anode protecting the steel substrate from corrosion.