Electrically conductive and corrosion resistant coating on Mg-Li alloy, part II: electroless nickel plating coating with a cut-off design for the galvanic corrosion
Xuanzheng Hao, Yifan Hu, Yuheng Zhen, Yanzhe Wen, Longguo Peng, Qi Xu, Yaojun Hou, Peng Zhou, Jintao Xiao, Xiaoxue Wang, Jingli Sun, Yong Yuan, Tao Zhang
Abstract
Electroless nickel (EN) plating could simultaneously offer protectiveness and electrical conductivity to Mg alloys, but micro-galvanic corrosion is the most detrimental factor that needs to be alleviated. In this work, various intermediate coatings, including electrically conductive conversion coating (EC-PCC), conventional phosphate chemical conversion coating (PCC) and plasma electrolytic oxidation coatings (PEO), were prepared before the EN process. Results show that, compared with Mg-Li alloys being coated with intermediate layers, the corrosion resistance of Mg-Li alloys after the EN process was severely deteriorated. This deterioration was ascribed to the futile design of cutting off the micro-galvanic corrosion. After sealing the pores in the PEO coating, a cut-off design of the galvanic corrosion was successfully designed, and the EN composite layer demonstrates a significant increase in corrosion resistance.