Preparation and Corrosion Behavior of Calcium Phosphate and Hydroxyapatite Conversion Coatings on AM60 Magnesium Alloy

An attempt has been made to improve the poor corrosion resistance of magnesium alloys and make these materials much more suitable for implant application by forming a hydroxyapatite (Ca-10(PO4)(6)(OH)(2), HA) coating. It was deposited on AM60 magnesium alloy by a two-step chemical method, i.e., calcium phosphate (CP) coating was first formed through a modified phosphating process, and then transformed to HA coating via alkali-heat-treatment. The effect of the alkali treatment time on the coating morphology and corrosion resistance was investigated. Polarization curves, electrochemical impedance spectroscopy (EIS) and immersion tests were employed to evaluate the corrosion behavior of the coatings in simulated body fluid (SBF) solution. The results show that the HA coating obtained through treating in the alkali solution for 1 hour exhibited improved corrosion resistance and a new finer layer formed on the coating surface after SBF immersion. (C) 2013 The Electrochemical Society. All rights reserved.