The Effects of B on the Microstructure and Corrosion Resistance of Zn–6Al–3Mg Alloy Coating

Abstract

Hot dip galvanized zinc‐aluminum‐magnesium steel plates are widely used in fields such as power communication, automotive manufacturing, and marine engineering due to their excellent corrosion resistance. The use of microalloying can further improve their corrosion resistance. The effects of B on the microstructure and corrosion resistance of Zn–6Al–3Mg (ZAM) alloy coatings are systematically examined. Data indicates that the eutectic structure of the coating progressively refines as B content increases, concomitant with a reduction in the thickness of the Fe2Al5 inhibition layer owing to the augmented formation of an Al‐rich phase at the surface. When the addition of B reaches 0.12%, the microstructure of the alloy coating is minimized, and there is no further reduction in the thickness of the Fe2Al5 inhibition layer. Moreover, the presence of B diminishes the corrosion current density and bolsters corrosion resistance. Optimal corrosion performance, indicated by maximal density and uniformity of surface corrosion products and the lowest corrosion current density, is achieved at a B addition of 0.12%. The judicious selection of B content is pivotal for enhancing the microstructural and anti‐corrosive properties of ZAM alloy coatings. Therefore, adding 0.12% B to ZAM alloy can effectively improve the microstructure and corrosion resistance of the alloy coating.