CORROSION MECHANISM AND MODEL OF ANODIZED FILM ON AZ91D MAGNESIUM ALLOY

The corrosion behavior of anodized film on AZ91D magnesium alloy in 3.5% neutral NaCl solution was investigated by saline immersion test. The results show that new corrosion points seldom occur on the surface of the said anodized film during the immersion time in 3.5% NaCl neutral aqueous solution after the first macroscopic corrosion point appears on the anodized film, while the previous corrosion point extends vertically or horizontally and turns into a corrosion pit which is in form of "strip". Moreover, the corrosion occurs firstly on α phase rather than β phase, when the corrosion of anodized film reaches the Mg alloy substrate. The corrosion products of anodized film on AZ91D magnesium alloy in neutral immersion solution were analyzed by XRD. A possible corrosion reaction and model about the corrosion of anodized film on AZ91D magnesium alloy in NaCl solution based on the experimental results is proposed.