Corrosion resistance of a super-hydrophobic dodecyltrimethoxysilane-based polypropylene coating on magnesium alloy AZ31

Corrosion resistance remains a significant challenge for magnesium (Mg) alloys, particularly in aggressive environments. To address this issue, the application of super-hydrophobic surfaces has emerged as a promising strategy. A composite coating was developed to enhance the corrosion resistance of AZ31 magnesium alloy by sequentially applying a dodecyltrimethoxysilane (DTMS) layer, followed by a polypropylene (PP) layer. The PP layer, composed of micro-scale spherical particles, exhibited exceptional super-hydrophobicity and chemical stability. Notably, the DTMS layer significantly improved the adhesion between the PP coating and the AZ31 substrate. Scratch tests indicated a critical load of 1482 mN for the DTMS/PP composite coating. Furthermore, the corrosion current density of the composite coating decreased to as low as 1.13 × 10⁻⁷ A·cm⁻², representing a two-order-of-magnitude reduction compared to the bare AZ31 substrate. Electrochemical impedance spectroscopy revealed a high charge transfer resistance of 5.47 × 10⁵ Ω·cm² for the DTMS/PP composite coating, underscoring its superior corrosion resistance. These results highlight the effectiveness of the newly developed coating in both mitigating corrosion and enhancing the durability of AZ31 magnesium alloy in aggressive environments.