Tunable corrosion protection of calcium carbonate (CaCO3) coating on biomedical Mg2Zn0.2Ca alloy

Abstract

Too fast corrosion of magnesium(Mg)-based materials is one of main concerns prior to their applications as biodegradable biomaterials. In present study, a CaCO3 coating on Mg alloy is developed via hydrothermal method to control the corrosion of Mg2Zn0.2Ca alloy. The morphology and anti-corrosion property of the CaCO3 protective coating are adjusted by the concentration of MgSO4 in coating preparation electrolyte. The results reveal that the presence of MgSO4 stabilizes the precipitation of metastable CaCO3 crystalline (aragonite and vaterite) and affects the structure and growth rate of the middle calcite layer on Mg alloy surface, which leads to the transformation of cubic calcite into small rhombohedral aggregates in the middle layer as the concentration of MgSO4 increases. Consequently, the corrosion protection property of the coating is significantly enhanced due to the increased compactness of the coating as the concentration of MgSO4 increases from 0 mM to 20 mM. Whereas, with further increase of MgSO4 concentration, the spindle-shaped calcite crystalline formed in the middle layer provides more penetrable boundaries, leading to a lower resistance for Mg substrate. Long-term immersion tests indicate the transformation of CaCO3 into calcium phosphate, which exhibits a great prospect for Mg alloys as orthopedic implants.

Keywords

• Magnesium alloy
• Calcium carbonate
• Magnesium sulphate
• Crystalline
• Anti-corrosion property