In-situ Investigation of Chemical Deposition Process of Calcium Phosphate Coating on Magnesium Alloy and Corrosion Behavior of the Coating in Normal Saline

A calcium phosphate coating was prepared on AZ31 magnesium alloy surface by chemical deposition. The morphology and phase constitution of the coating was analyzed by scanning electron microscopy and X-ray diffractometer. The chemical deposition process and corrosion behavior of the coating in normal saline was in-situ investigated by electrochemical noise technique. The results showed that a compact calcium hydrogen phosphate dihydrate (DCPD) coating was formed on AZ31 substrate after deposition for 3 h. The corrosion rate of the coated sample was obviously less than that of AZ31 substrate. Localized corrosion occurred on AZ31 substrate in a short period and several pits were observed. It took relative long time for the coated sample to suffer localized corrosion. Corrosion developed along the grinding trace, meanwhile the initial corrosion area stoped to develop.