Deposition and initial stages of corrosion degradation in Hank’s solution of chitosan-phosphate coatings on WE43 Mg alloy

Chitosan-based coatings can be effectively used for tailoring degradation profiles of biomedical magnesium alloys. In this work, chitosan-phosphate coordinated coatings were for the first time deposited on WE43 magnesium alloy by the electrophoretic deposition approach. Scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and Fourier-transform infrared spectroscopy were employed to characterize the surface morphology and composition of the coatings, along with dynamic and classical electrochemical impedance spectroscopy were used to evaluate initial stages of their degradation profiles in Hank’s solution. The results demonstrated that incorporation of small amounts of phosphate ions into the chitosan matrix significantly modified the morphology of the coatings and improved their short- and long-time corrosion resistance, with impedance values up 2.0–3.5 times higher than in the case of phosphate-free coatings. Phosphate ions also contributed to the formation of a thin conversion phosphate layer on the surface of Mg substrate during the deposition of the coatings, which also plays important role on corrosion resistance. Obtained results allowed to propose detailed deposition and corrosion mechanisms of the obtained coatings.