Corrosion resistance mechanisms of spin-coated superhydrophobic coatings on AZ31B Mg alloy

Abstract Magnesium (Mg) alloys possess high specific strength and low density but suffer from poor corrosion resistance, which restricts their broader application in marine and biomedical environments. To overcome this limitation, a superhydrophobic epoxy/polytetrafluoroethylene (PTFE) nanocomposite coating was developed on AZ31B Mg alloy using a spin-coating process. This study aims to clarify how coating architecture and uniformity influence corrosion resistance and long-term durability. Electrochemical analyses revealed that the uniformly coated specimens had a significantly lower corrosion current density (1.85 × 10 –6 A cm −2 ) and higher polarization resistance (3.55 × 10 4 Ω·cm 2 ), resulting in a corrosion rate of only 0.022 mm/year, nearly 94% less than that of the bare substrate. Complementary electrochemical impedance spectroscopy (EIS), salt-spray, and outdoor exposure tests confirmed that the bilayer coating effectively suppresses electrochemical degradation and maintains hydrophobicity over time. These findings demonstrate the necessity of developing architecture-optimized superhydrophobic coatings to achieve durable and scalable protection strategies for lightweight Mg alloys.