Partially phosphorylated poly(vinyl alcohol) - A promising candidate in corrosion protection of magnesium for the biomedical industry?

Partially phosphorylated poly(vinyl alcohol) (PPVA) as anticorrosive coating for AZ31 magnesium alloy was investigated in Hank's Balanced Salt Solution (HBSS). Four phosphoric acid levels were used to modify PVA, resulting in four PPVA products. They were characterized using thermogravimetric analysis (TGA), water contact angle (WCA), and swelling test. PPVA-coated Mg alloys were evaluated using hydrogen evolution, cathodic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). TGA indirectly revealed crosslinked regions in the PPVA structure that increased with acid content. WCA and hydrogen evolution tests suggested that PPVA is a promising polymer for biomedical applications. Corrosion tests showed that the PPVA with 10% acid addition significantly improved the impedance modulus and lowered the cathodic kinetics compared to uncoated samples. The findings of the study suggested that the acid addition in PVA must be at least 10 % to guarantee improved corrosion resistance in HBSS, which indicates this material has potential for biological applications.