Effect of deposition temperature on microstructure, corrosion behavior and adhesion strength of Zn-Mg coatings on mild steel

Zn-Mg alloys are strong candidates for the protective coating materials on steel products due to their excellent corrosion resistance compared to pure Zn. In previous research, sputtered Zn-Mg coatings with a high Mg content (above 27 at.%) exhibited a featureless amorphous structure that improved the corrosion resistance of the coatings. However, these Zn-Mg coatings showed a brittle fracture during deformation, resulting in a decrease in adhesion strength. Accordingly, in the present study, to improve the adhesion strength of Zn-Mg coating, the deposition temperature of the Zn-Mg coatings was controlled and the effects of the deposition temperature on the coating microstructure, corrosion resistance, and adhesion strength of the synthesized coatings were investigated. The results revealed that the deposition temperature significantly affected the microstructure as well as the coating properties. Zn-Mg coatings synthesized below 50 °C showed a featureless amorphous microstructure, while porous crystalline Zn-Mg coatings were synthesized above 100 °C. Even though the corrosion resistance of the Zn-Mg coatings decreased slightly as the deposition temperature increased, all of the Zn-Mg coated steel samples exhibited passivation behavior in the corrosion environment. As the deposition temperature of coating increased above 100 °C, the fracture and detachment phenomena of the Zn-Mg coatings during deformation decreased. These results revealed that the adhesion strength of Zn-Mg coating could be improved by controlling the deposition temperature. •Zn-Mg coatings were synthesized at various deposition temperatures on steel substrates.•Microstructure of coatings varied depending on the deposition temperature.•Amorphization of the Zn-Mg coating was verified through theoretical calculations.•All the Zn-Mg coatings exhibited passivation behavior during the corrosion test.•Adhesion of Zn-Mg coatings could be improved by deposition temperature control.