Effect of molybdenum on the corrosion of low alloy steels in synthetic seawater

The alloying effect of Mo on the seawater immersion corrosion for low alloy steel was investigated using weight loss tests and electrochemical impedance spectroscopy (EIS) in seawater. The Mo-containing low alloy steel showed an excellent corrosion resistance by the long immersion test due to the formation of homogeneous rust layer preventing active dissolution. SEM and XPS analyses were conducted to observe cross-sectional images of rust layer and indentify chemical composition of oxide formed on the surface after immersion test. The results revealed that the MoO₄^2- ions which were oxidized from Mo form the compounds which disturb the approach of aggressive ions.