Abstract
A functional composite coating system was developed on VW75 magnesium alloy to address the trade-off between corrosion resistance and electrical conductivity. A micro-arc oxidation (MAO) inner layer incorporating Ta2O5 particles was first fabricated, followed by the deposition of an epoxy resin topcoat doped with PEDOT: PSS and cobalt (Co) powder. The microstructure, phase composition, and electrochemical properties of the composite coatings were systematically characterized. The results indicated that the incorporation of Ta2O5 particles significantly enhanced the compactness of the MAO layer, with optimal corrosion resistance achieved at a Ta2O5 concentration of 6 g/L. When the concentration of Ta2O5 is 6 g/L, the pore size distribution of the coating is moderate, which can form a strong bonding force with the epoxy coating. The subsequent application of the modified epoxy topcoat further augmented the protective performance via a pore-sealing effect. Notably, the corrosion resistance was positively correlated with the content of dopants. Furthermore, the PEDOT: PSS and Co fillers facilitated the formation of a conductive percolation network within the epoxy matrix, thereby imparting excellent electrical conductivity to the composite. These findings demonstrate the potential of this dual-layer coating strategy for protecting magnesium alloys in harsh marine environments.