Microstructure and Corrosion Behavior of Zinc-magnesium Alloy Coatings Prepared by Vacuum Evaporation

Magnesium layers with a certain thickness on conventionally galvanized steel sheets were prepared by the vacuum evaporation coating technology.And then the coated sheets were treated by alloying and annealing processes in order to obtain novel Zn-Mg alloy coatings.The surface,cross and cutting edge section microstructure of Zn-Mg alloy coatings were analyzed by SEM and EDS.The anti-corrosion performance of Zn-Mg alloy coatings were studied by salt spray test and electrochemical experiment.Coatings themselves and the corrosion products were analyzed by X-ray diffraction.It was proved that the Zn-Mg alloy coating was mainly composed of MgZn2 and other zinc-magnesium alloy phase.The Zn-Mg alloy coating has even more excellent corrosion resistance and better corrosion resistance of cutting edges than conventionally galvanized steel sheet.Regarding to the macro performance,the corrosion products zinc magnesium coating are more compact than those of the pure zinc coating,and the electrochemical behavior of zinc magnesium coating has a smaller corrosion current density and higher polarization resistance.