Sacrificial Magnesium Film Anode for Cathodic Protection of Die Casting AZ91D Alloy

摘要

The coatings on magnesium alloy usually act as a corrosion barrier to the environment. However, the coating must be crack free for applications otherwise the substrate material under the crack becomes local anode, leading to severe local corrosion. In present study, magnesium film was deposited on AZ91D specimen, acting as a sacrificial anode. The corrosion properties of the Mg-film coated specimen were estimated by electrochemical polarization experiments and salt-spray tests. Resistively heated tungsten coil heating system was used for vaporizing source. The Ecorr values of the coated specimens were -1.7～-1.66V (AgCl), which was evidently lower than that of the substrate material (AZ91D diecast specimen). According to the above electrochemical analyses, the magnesium coating could be used as a distributed sacrificial anode, cathodically protecting the substrate (AZ91D diecast specimen).