Challenges and solutions of cathodic protection for marine ships
Likun Xu, Yonglei Xin, Li Ma, Haibing Zhang, Zhifeng Lin, Xiangbo Li
Abstract
Cathodic protection (CP) has been successfully used, in combination with organic coatings, to prevent ship hulls and ballast tanks from sea water corrosion. Although CP technology has been developed significantly in the past decades, some problems remain related to the CP materials applied to ship hulls and ballast tanks. In an impressed current CP system for ship hulls, auxiliary anodes are one of the crucial components, which should have high electrochemical activity and long service life. Impressed current anode with mixed metal oxide (MMO) coated titanium has been widely applied. However, the performance of MMO anode still needs to be improved especially when working at a large current density and in low temperature seawater. Sacrificial anodes such as zinc or aluminium alloys have been used to protect ballast tanks, where the electrochemical properties of these anodes will degrade with cyclic exposure to atmosphere and seawater. Moreover, high strength steels are often used for structural components of high-performance vessels, which suffer from hydrogen embrittlement if inappropriate CP potential is applied. These challenges and solutions of CP for marine ships have been reviewed and discussed in this paper.