Enhanced PVDF Coating via Zr-Based Pretreatment on AZ31 Magnesium Alloy

Magnesium alloys are promising biodegradable orthopedic implant materials, but their clinical translation is hindered by rapid, unregulated corrosion in physiological environments. Polyvinylidene fluoride (PVDF) coating has attracted substantial attention for addressing the issue above. However, it suffers from insufficient interfacial adhesion to Mg alloy substrates. In this work, we propose a Zr-based pretreatment strategy to enhance PVDF coatings. The pretreatment was performed via a chemical conversion deposition method, which fabricated a Zr-based film on AZ31 magnesium alloy and greatly promoted the adhesion of the following PVDF coating. Interface analysis showed that coating adhesion was improved from 0.44 MPa to 2.48 MPa. In light of this, corrosion protection performance was significantly improved. Electrochemical tests in simulated body fluid revealed the enhanced PVDF coating shifted the corrosion potential from −1.594 V to −1.392 V and reduced the corrosion current density by over five orders of magnitude. Immersion tests also showed stable pH level, low weight loss, and good hydrophobicity with the enhanced PVDF coating. In summary, the enhanced PVDF coating provides excellent corrosion protection for magnesium alloys, thus boosting their biomedical use.