Corrosion Behavior of AZ31 Magnesium Alloy with Calcium Phosphate Coating in Hank′s Solution

A calcium phosphate coating was fabricated on AZ31 magnesium alloy surface by electrochemical deposition method. The morphology and structure of the coating were analyzed by three-dimensional digital microscope and X-ray diffractometer. The corrosion behaviors of AZ31 magnesium alloy and calcium phosphate coating in Hank′s solution were investigated by the hydrogen evolution testing and the potentiodynamic scan technique. The results showed that the deposited coating predominately consists of flake-shape brushite (CaHPO4·2H2O) crystallites. The coating can decrease the corrosion rate of AZ31 substrate immersing stage in Hank′s solution. At the initial stage, the corrosion current density decreased 2 orders of magnitude. With the degradation of the coating, the protectivity of the coating decreased and obvious localized corrosion occured on the sample surface.