Nanostructured amorphous magnesium phosphate/poly (lactic acid) composite coating for enhanced corrosion resistance and bioactivity of biodegradable AZ31 magnesium alloy

•The uniform and crack-free nAMP/PLA nanocomposite were fabricated on AZ31 alloy.•The nAMP particles homogeneously distributed in PLA matrix.•The corrosion resistance of AZ31 alloy was markedly enhanced by nAMP/PLA coating.•The addition of nAMP promoted biomineralization of PLA film and AZ31 substrate. Due to the combination many interesting properties, magnesium alloys have attracted considerable interest as suitable metallic biomaterials for bioresorbable orthopedic implants. Nevertheless, their fast degradation in physiological environments pose challenge for their practical applications. Here, we report that spin coating of composites of nano amorphous magnesium phosphate (nAMP) and poly (lactic acid) (PLA) on AZ31 magnesium alloy. The idea is to use the nAMP/PLA composite film while tailoring the degradation and enhancing the bioactivity of magnesium alloys. SEM examinations show that as-deposited nAMP/PLA film is smooth, crack-free and the nAMP particles are well distributed in PLA matrix. The electrochemical test including potentiodynamic polarization and EIS associated with immersion test results reveal that the corrosion activities of nAMP/PLA coated AZ31 magnesium alloy in SBF are markedly suppressed. Furthermore, it is seen that massive bone-like apatite precipitates formed on surface of nAMP/PLA coated sample, which is indicative for the superior biomineralization capability achieved by nAMP/PLA nanocomposite coating. Thus, the nAMP/PLA composite coating has great potential to be employed as the protective and bioactive coating on biodegradable magnesium alloys for orthopedic applications.