Statistical design of the parameters involved in the obtainment of a biodegradable phytate coating over AZ31 alloy for possible endoprosthetic temporary applications

Abstract Phytic acid has been used to generate phytate conversion coatings on magnesium and magnesium alloys, in order to improve their corrosion resistance without jeopardizing their biocompatibility and biodegradability. In the present work, statistical designs were used to determine the optimal levels of the parameters for the formation of a conversion coating on AZ31 Mg alloy, with the aim of using it for further endoprosthetic temporary applications. Both parametric and non-parametric statistical tests were used to determine the optimum processing parameters of the coating on the AZ31 magnesium alloy, which are: phytic acid concentration of 0.5%v/v, pH = 5, treatment time of 30 min and treatment temperature of 29 °C. The surface morphology, chemical nature and corrosion resistance of the coatings were examined by SEM, EDS, XFR spectroscopy and electrochemical measurements: potentiodynamic polarization curves and polarization resistance. The pH = 5 phytate coatings showed less micro-cracks and more uniformity than those obtained at pH = 2. The coatings' thickness increased with treatment time. Besides, the statistical analysis demonstrated there is a significant effect of the phytic acid concentration over R p , and that this effect depends on treatment time.