[Introduction] The formation mechanism of needle-like skip plating defect on the surface of high-strength steel bracket appearing in the modified Sendzimir continuous hot-dip zinc coating line was discussed and some corresponding control measures were proposed in this paper. [Method] The morphology and element distribution at the position of needle-like skip plating defect were analyzed by laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). [Result] The needle-like skip plating defects were randomly distributed as black pinholes on the surface of steel strip. A significant enrichment of alloy elements such as Cr and Mn was found on the subsurface of the skip plating position. These alloy elements underwent external oxidation on the surface of steel strip, leading to a decrease in the platability of its surface, resulting in skip plating finally. [Conclusion] The skip plating of steel strip can be effectively prevented by conducting pre-oxidation of steel strip during heating phase in open fire, as well as promoting the internal oxidation of alloy elements during annealing phase.
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