Microstructural and Corrosion Resistance Evaluation of Hot-Dipped Al-Zn-Si Alloy-Coated Steel

The article describes a novel Al-Zn-Si alloy hot-dip coating on steel, coating characterization and performance evaluation. Cross-sectional SEM micrographs showed that the coating consists of two layers- thick Al-Zn-Si alloy layer on the top and a thin Al-Fe-Si intermetallic layer underneath toward the interface. The outer Al-Zn-Si alloy layer is composed of primary aluminum-rich (α-Al) dendrites along with uniform distribution of Si. EDS and XRD analysis identified Al-Fe-Si intermetallic layer as Al 8 Fe 2 Si phase. Potentiodynamic polarization study displayed superior corrosion properties of the coating compared to commercial aluminized steels. Corrosion rate (in mpy) was found to be six times lower compared to galvanized coating with a similar corrosion potential. Furthermore, salt spray test life of coating more than 2000h confirmed superior corrosion properties than GI coating.