Hybrid chondroitin sulfate-tailored phosphate coatings for improved corrosion and wear resistance of WE43 magnesium alloy

Biodegradable magnesium (Mg) alloys are useful for bone screws, but their anti-corrosion and anti-wear coatings properties may be inadequate in vivo. Herein, a hybrid MgKPO₄·6H₂O (MKP)/chondroitin sulfate A (CSA) coating with a uniform and crack-free morphology is prepared on the WE43 Mg alloy by a hydrothermal treatment. The corrosion current density (4.219 × 10⁻⁶ A/cm²) of the MKP-CSA coating is an order of magnitude smaller than that of the bare Mg, and the hydrogen evolution rate (0.0005 mL·cm⁻²·h⁻¹) and corrosion rate (0.47 ± 0.01 mm/y) improve significantly as well. Tribologically, the coating shows an average friction coefficient of 0.239 ± 0.019 and a wear rate of 17.94 × 10⁻⁵ mm³/N·m, which are 35.6% and 46.4% less than those of the Mg alloy. Our study demonstrates that the complex formed by chelation of CSA with Mg²⁺ provides in situ nucleation sites for MKP. The enhanced corrosion resistance of the hybrid coating stems from the optimized structure, and the wear resistance can be attributed to the higher adhesion strength and hardness, and the combination of the relatively hard inorganic material of MKP and soft polymer of CSA. The results reveal a new strategy to fabricate hybrid inorganic-organic coatings on biodegradable Mg alloys with excellent corrosion and wear resistance for clinical applications. © 2025 Elsevier B.V.