Zinc coatings to protect sheet and other steel products are commonly applied by electroplating (cold galvanizing) or immersion (hot dip galvanizing). Adding such alloying elements as magnesium to pure zinc improve the performance of the coating in corrosion applications. Recently, physical vapor deposition process has been considered as an alternative method for creating zinc-based coatings due to the process uniformity and control over coating thickness. Few studies have been published regarding the thickness changes of zinc-magnesium layers, and most of the research has investigated the effect of magnesium content. In this study, dual-layer zinc-magnesium coatings of different thicknesses were deposited on a steel substrate using a magnetron sputtering process. Subsequently, annealing was performed at a temperature of 200 degrees Celsius for the formation of intermetallic phases between zinc and magnesium. After heat treatment, the specimens were analyzed and compared using grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The adhesion of the coatings was measured using a bending test, and the corrosion resistance of the specimens was eva‎luated through electrochemical tests such as potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5% NaCl solution and compared with the galvanized coating. The results showed that after annealing, the coatings formed equiaxed grains with a dense structure. X-ray diffraction identified the presence of intermetalic compounds, including MgZn2 and Mg2Zn11, within the coating. Increasing the thickness of the coating lead to an increase in intermetalic compounds and residual stress, which affect the coating adhesion. The results of the electrochemical tests demonstrated that zinc-magnesium coated steel, after 45 minutes, exhibited good corrosion resistance with a corrosion current density of 17 μA/cm2, compared to the conventional galvanized coating with a current density of 97 μA/cm2. This emphasizes the positive impact of magnesium in thin zinc layers produced by physical vapor deposition.

فخرالدين اشرفي زاده

عبدالمجيد اسلامي , نويد سعيدي