PEDOT: PSS/MAO@Co organic composite coating: Enhancement of corrosion resistance and conductivity properties of VW75 magnesium alloy

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 Ta 2 O 5 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 Ta 2 O 5 particles significantly enhanced the compactness of the MAO layer, with optimal corrosion resistance achieved at a Ta 2 O 5 concentration of 6 g/L. When the concentration of Ta 2 O 5 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.