Effect of Zn Transition Layer on Properties of Vacuum Deposited Zn-Mg Coating

Abstract

Zinc coatings have been served as a barrier and a galvanic protection for steel products for over a century. However, with the depletion of zinc resources, it becomes an urgent issue to obtain a new type of zinc coating that uses less zinc and has higher corrosion resistance. In order to develop Zn/ZnMg coatings with better corrosion resistance than traditional galvanized steel and suitable for advanced high strength steel, the vacuum thermal evaporation technique was used to simultaneously deposit Zn/ZnMg coating onto interstitial free steel plates and single-crystal silicon wafers in a high vacuum environment. The microstructure, morphology, adhesion and corrosion resistance behavior of the Zn/ZnMg coating were studied by scratch test, salt spray test and electrochemical method. The results shows that the grain size in the Zn/ZnMg coating tended to increase with the increase of the substrate temperature. After deposited the pure Zn transition layer, the adhesion of the coating has been obviously improved. When the substrate temperature was increased to 200°C, the obtained coating exhibited strong corrosion resistance.