Study of the effect of Mg(OH)2/MgO thin films obtained by sputtering on the corrosion behavior of ZK60A Mg alloy
Magnesium alloys are attractive for several industrial applications due to a combination of suitable mechanical properties, low cost and ease of processing. Nonetheless, their widespread use is restricted due to limitations regarding their intrinsic low corrosion resistance. Thin films obtained by physical vapor deposition (PVD) processes may be used as a protection method for magnesium alloys. In this work, MgO/Mg(OH)2 films were deposited on the ZK60A magnesium alloy using reactive sputtering. The aim was to increase the corrosion resistance of the base alloy. The crystalline phases of the deposited films were analyzed by X-ray diffractometry (XRD). X-ray photoelectron spectroscopy (XPS) was employed to analyze the surface chemical composition of the deposited films. The morphology of the thin films was examined by scanning electron microscopy (SEM). The electrochemical behavior was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization tests. The tests were conducted in 3.5 wt.% NaCl solution at room temperature. The results showed that MgO/Mg(OH)2 mixed films were successfully obtained. The corrosion resistance was enhanced with respect to the uncoated ZK60A alloy substrate, depending on the deposition conditions.