Impact of zinc ion addition on corrosion of EH40 steel in natural seawater

Zinc ion is a common heavy metal in marine pollution, but its impact on corrosion of steels without passive films in natural seawater is far from being investigated. In this study, the impact of zinc ion addition (1.5 and 15 mmol/L) on corrosion of EH40 steel commonly utilized for building ships and offshore platforms was studied by numerous methods and technologies. It was found that EH40 steel corrosion was inhibited with the addition of zinc ion, and corrosion inhibition efficiency increased with the concentration added. The deposited ZnO and Zn(OH)(2) on the steel surface was believed to hamper electron transfer, thus inhibiting corrosion. Meanwhile, the bactericidal zinc ion and ZnO mitigated the activity of microorganisms in biofilms to reduce the damage caused by microbiologically influenced corrosion. But pitting corrosion was enhanced with a high concentration of zinc ion added due to the inhomogeneity of ZnO layers.