Influence of Fe content and Cl⁻ concentration on the microstructure and electrochemical properties of Al-8Si-xFe coating alloys

Hot-dip aluminising technology is widely used in modern engineering, but Fe dissolution into the alloy during production degrades coating quality and performance. This study investigated the influence of Fe on the microstructure and corrosion resistance of Al-8Si coating alloys using SEM, TEM, EBSD and electrochemical methods. With increasing Fe content, specific phases precipitated sequentially: at 0.3 wt.% Fe, FCC Al, the Si phase, and the ternary eutectic Al₉Fe₂Si₂ formed; at 1 wt.% Fe, the primary Al₉Fe₂Si₂ phase emerged. As the Fe content increased, the corrosion current density first decreased but then increased. A lower Cl⁻ concentration significantly elevated the electrode potential: in low Cl⁻ solutions, a dense oxide film formed on α-Al, while Al₉Fe₂Si₂ underwent preferentially oriented corrosion and fragmentation. This study reveals the coupling mechanism of Fe-rich phase evolution, micro-galvanic corrosion and passivation film stability, providing a theoretical basis for optimising hot-dipped Al alloys resistant to Cl⁻ corrosion.