Influence of an annealing heat treatment on the microstructure, ductility, and corrosion resistance of a chromated 55 wt.% Al-Zn coated steel sheet

The effect of an annealing heat treatment on both the ductility and corrosion resistance of a chromated hot-dip 55 mass% Al-Zn coated steel sheet is investigated. The present results suggest that the heat treatment improves coating ductility but impairs the overall corrosion resistance due to a decrease in the protective effect of the passivation layer and possibly due to the decrease in the amount of interdendritic zinc. Based on these results, it is concluded that the benefits of the heat treatment to improve ductility have to be carefully assessed with reference to the intended application due to its adverse effect on the corrosion resistance.