Corrosion behaviors of different metal-coated steel sheets after resistance spot welding
[Introduction]The effect of spot welding on corrosion behavior of steel sheets with different coatings is worthy of study.[Method]Resistance spot welding was conducted on the surfaces of Zn-coated steel and Zn-Al-Mg alloy-coated steel sheets.The morphology and element distribution at and around the welded spots were analyzed by scanning electron microscopy and energy-dispersive spectroscopy.The corrosion behaviors of Zn-coated steel and Zn-Al-Mg alloy-coated steel before and after resistance spot welding in the same environment were studied by neutral salt spray test and electrochemical impedance spectroscopy.[Result]There were many bumps and pits at the edge of welded spots for Zn-coated steel,but not for Zn-Al-Mg alloy-coated steel.The substrates at the welded spots of the both steel sheets were partially exposed due to the volatilization of zinc element during welding.Regardless of spot welding or not,the corrosion resistance of Zn-coated steel in neutral salt spray test was not as good as that of Zn-Al-Mg alloy-coated steel.[Conclusion]Resistance spot welding can easily lead to partial damage of the coatings on steel sheets and affect their corrosion resistance.
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