Effect of Element Mo on the Corrosion Resistance of Shipbuilding Steel for Inner Bottom Plate of Cargo Oil Tanks

Corrosion experiments of shipbuilding steels were conducted in a simulated corrosion environment around inner bottom plate of cargo oil tank (COT). Effect of Mo on the corrosion resistance was investigated by means of electron probe microanalysis and electrochemical analysis. The results indicate that with the addition of Mo, the overall corrosion resistance improved, particularly in terms of enhancing corrosion uniformity and inhibiting pitting corrosion. The reasons may be due to refining of microstructure, increase of free corrosion potential and promotion of Cu enrichment in the passive film. However, when the mass fraction of Mo was more than 0.1%, the microstructure was over refined, and the corrosion resistance declined due to a decrease of reaction free energy of overall surface.