Causes of pitting defects on hot-rolled galvanized steel sheet were studied by means of systematic surface examination,detailed microstructure analysis and precise chemical composition testing.The results show that aberrant dew point conditions within the annealing furnace lead to an insufficiently reducing atmosphere,which induces the oxidation and formation of iron oxide on the surface of the steel sheet,so that the surface wettability of hot-rolled substrate is insufficient during galvanizing,thereby impeding the formation of the Fe-Al inhibition layer and leading to pinhole leakage in the zinc coating.These pinhole leakages disrupt the flow of the zinc liquid after the steel sheet is discharged the zinc pot,eventually manifesting as visible pitting defects on a macroscopic scale.
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