Surface anodization of Ti-containing high entropy alloy to improve poly (methyl methacrylate) coating performance in phosphate buffered saline

This study investigates the influence of anodized surface interfaces on the performance of poly (methyl methacrylate) (PMMA) coatings deposited onto a newly developed high entropy alloy (HEA) in a phosphate-buffered saline (PBS) environment. Electrochemical anodization was performed at varying voltages (10–30 V) to optimize oxide layer formation for improved interfacial bonding. Anodization at 20 V produced a compact, homogeneous porous oxide film that significantly enhanced the corrosion resistance of the HEA substrate. The corrosion current density was reduced from 6.659 µA/cm² (bare HEA) to 0.1209 µA/cm² (HEA20V), while the charge transfer resistance increased markedly from 115.7 to 11,158.0 kΩ·cm² for PMMA-coated anodized samples. Mechanical characterization revealed a substantial improvement in micro indentation hardness, increasing from ∼0.8 MPa (PMMA/Bare) to ∼1.25 MPa (PMMA15/HEA20V), and ∼1.4 MPa for PMMA20/HEA20V. Scratch resistance also improved significantly, with acoustic emission signals indicating near-complete suppression of interfacial failure in anodized samples. These findings demonstrate that surface anodization not only promotes superior adhesion and film uniformity but also enhances the corrosion protection and mechanical robustness of PMMA coatings. The synergistic interface between the anodized HEA and PMMA coating offers great promise for orthopedic implant applications.