Synthesis and characterization of magnesium phytic acid/apatite composite coating on AZ31 Mg alloy by microwave assisted treatment

Highlights: • Microwave assisted apatite bilayer deposition on magnesium phytic acid coating • The pH value of microwave solution affected the structure of apatite coating. • The composite coating greatly improved the corrosion resistance of AZ31 substrate. • The composite coated sample showed rapid mineralization with moderate degradation. - Abstract: To improve the corrosion resistance and bioactivity of AZ31 magnesium alloy, a crack-free magnesium phytic acid/apatite composite coating was synthesized on AZ31 substrate via chemical conversion deposition and followed a rapid microwave assisted treatment. The influences of pH values of the microwave solution on the morphology, composition and corrosion resistance properties of the composite coating were investigated. An apatite coating with bilayer structure was completely covered the magnesium phytic acid conversion coating after microwave radiation in the solution of pH 6.5, which reached the thickness of ~7.0 μm. During the electrochemical and immersion tests in simulated body fluid (SBF), the samples with composite coating exhibited a remarkably improved corrosion resistance, slower degradation rate and rapid inducing of Ca-P apatite deposition, suggesting that the composite coating could provide a long-time protection for substrates and promote the bioactivity of AZ31 magnesium alloys. Moreover, after 5 days of incubation, the composite coating showed non-cytotoxicity, good osteoblast adhesion and proliferation.