Optimization of Hybrid PEO/P(L/G/TMC) Coatings on WE43B Magnesium Alloy: Effect of Polymer Layer Number on Surface Properties

Magnesium alloys are promising materials for orthopedic applications due to their biodegradability and mechanical properties compatible with bone. However, their rapid degradation in physiological environments limits clinical use. In this study, WE43B magnesium alloy was coated with a PEO layer followed by a P(L/G/TMC) polymer applied via ultrasonic spraying. The influence of polymer layer number (10, 20, 30) on coating properties was systematically investigated. Scanning electron microscopy (SEM) analysis revealed an approximately fourfold reduction in porosity after polymer deposition, with progressive pore filling at higher layer numbers, while Fourier transform infrared spectroscopy (FT-IR) mapping indicated uniform polymer coverage. Compared to PEO alone, polymer-modified samples exhibited an approximately 7-fold increase in water contact angle, a ~50% reduction in surface roughness, and improved adhesion. Degradation-related analyses, including ion release, post-immersion SEM, and scanning acoustic microscopy (SAM), indicated that increasing polymer thickness effectively limited degradation processes. Ion release decreased by ~40–50% for the 30-layer coating compared to PEO, with the most pronounced reduction observed between the uncoated PEO and polymer-modified samples. These results demonstrate that the number of polymer layers plays a key role in controlling the barrier properties and stability of hybrid PEO/polymer coatings under simulated physiological conditions.