Enhanced corrosion resistance,mechanical stability,and biocompatibility of AZ61 magnesium alloy via alumina-selenium composite coatings for biomedical implant applications

Abstract

This study successfully applied an alumina (Al₂O₃)–selenium (Se) composite coating to AZ61 magnesium alloy through dip coating, aiming for potential biomedical applications such as cardiovascular stents and implant devices. The corrosion resistance of the coatings was significantly enhanced, as demonstrated by electrochemical tests in simulated body fluid (SBF). The S4 sample (coated for 3 h) exhibited high corrosion resistance, with its corrosion current density decreasing from 2.10 × 10⁻⁷ A/cm² (bare) to 2.42 × 10⁻⁹ A/cm², representing a reduction of over 1.826 × 10⁻⁹ mpy in the Corrosion Resistance value after various immersion times. Mechanical tests confirmed increased surface hardness, rising from 35.4 HV in the bare alloy to 47.3 HV for S4, along with reduced porosity, reaching up to 0.1097. Microstructure analyses confirmed the formation of Al₂O₃ and Se phases, revealing a uniform coated morphology on the carbon support across all samples; the S4 sample displayed the fewest defects. Surface roughness increased from 0.140 µm (bare) to 3.675 µm (S4), and contact angle decreased from 85.4° to 25.2°, promoting hydrophilicity and cellular adherence. Biocompatibility tests indicated 86.01% cell viability (MTT assays) and 4.70% haemolysis, classifying the coated alloy as non-haemolytic and non-cytotoxic. Overall, the Al₂O₃–Se composite coatings on S4 demonstrated superior performance in corrosion resistance, mechanical strength, and biocompatibility, suggesting these coatings are promising for long-term, stable, safe, and bioactive Mg-based implants.