Corrosion behaviors in physiological solution of cerium conversion coatings on AZ31 magnesium alloy

In this paper, a non-toxic Ce-based conversion coating was obtained on the surface of bio-medical AZ31 magnesium alloys. The micro-morphology of the coating prepared with optimal technical parameters and immersed in physiological solution (Hank's solution) in different time was observed by scanning electron microscopy (SEM), composition of the cerium conversion coating and corrosion products in Hank's solution were characterized by X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), respectively. In addition, the corrosion property in Hank's solution was studied by electrochemical experiment and immersion test. The results show that the dense Ce-based conversion coating is obtained on the surface of AZ31 magnesium alloys in optimal technical parameters and the conversion coating consists of a mass of trivalent and tetravalent cerium oxides. The cerium conversion coating can provide obvious protection of magnesium alloys and can effectively reduce the degradation speed in Hank's solution. Also the degradation products have little influence on human body.

► We obtained the compact cerium conversion coating with tiny and thick cracks on biomaterial AZ31 magnesium alloys. ► The coating is made of CeO2, CeO, Ce2O3, MgO, Mg(OH)2 and Al2O3. ► The conversion coating can slow down the degradation of magnesium alloys immersed in Hank's solution for 24 h. ► The degradation elements were the essential element and a platform for forming a natural bone. ► Cerium conversion coating had better corrosion resistance than bare sample via electrochemical tests in Hank's solution.