A metasilicate-based ceramic coating formed on magnesium alloy by microarc oxidation and its corrosion in simulated body fluid

We report a strategy to prepare biocompatible metasilicate-based ceramic coatings by microarc oxidation (MAO) on AZ91D magnesium alloy in sodium silicate solution with Ca(H2PO4)2 additive. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to assess the phase composition and microstructure of the coatings. The corrosion behavior of the coated samples was evaluated by electrochemical and immersion tests in simulated body fluid (SBF). The results show that the corrosion resistance of AZ91D alloy is significantly improved due to the formation of dense coatings with biocompatible CaSiO3, CaMgSiO4 and Mg2SiO4 phases. Increasing Ca(H2PO4)2 content in the based sodium silicate leads to better corrosion resistance of AZ91D alloy. The results suggested a promising method for surface modification of degradable magnesium alloy as biomedical applications.

► The effects of Ca(H2PO4)2 in the sodium silicate based electrolyte on MAO coatings were investigated.
► Biocompatible MAO coating with CaSiO3, CaMgSiO4 and Mg2SiO4 phases was prepared.
► Corrosion resistance of the MAO coatings was improved due to the addition of Ca(H2PO4)2.