Corrosion resistance of zinc-magnesium-aluminium alloy coated steel in marine atmospheric environments

Abstract

In this study, a salt-spray accelerated experiment was conducted as a simulated corrosion test of hot-dip galvanised zinc-magnesium-aluminium-coated alloy steel under a simulated marine atmospheric environment. In addition, scanning electron microscopy, confocal microscopy, X-ray diffraction, and electrochemical workstations were used to conduct analyses on the macro-morphology, microstructure, corrosion product composition, etc. after the corrosion test. Furthermore, the role of Mg in the corrosion resistance of zinc-magnesium-aluminium alloy steel sheets was determined. The research results indicated that in a marine atmospheric environment, zinc-aluminium-magnesium alloy steel has excellent corrosion resistance, and its external coating provides protection to the substrate. In a marine atmospheric environment, the corrosion products of zinc-magnesium-aluminium alloy steel mainly include Al2O3, AlOOH, zinc hydroxychloride (Zn5(OH)8Cl2·H2O), layered bimetallic hydroxides (Mg6Al2(OH)16CO3·4H2O), ZnO, and MgCO3·H2O. The addition of magnesium to galvanised sheets facilitates the formation of insoluble corrosion products, which protect the iron substrate.