To improve the surface appearance, electrodeposition coating suitability, workability and chipping resistance of steel at a low cost, on the surface of a hot dip galvanized steel sheet after skinpass rolling, by forming an electrogalvanizing layer or an Fe-Zn alloy electroplating layer having a specified Fe content by specified coating weight.
One side or both sides of a steel sheet are applied with hot dip galvanizing at the thick coating weight of about 90 to 120 g/m2 per side. Next, the hot dip galvanized steel sheet is subjected to skinpass rolling, desirably at about ≥0.5% draft to smoothen the surface. After that, on the surface of the steel sheet, an electrogalvanizing layer of ≥1 g/m2 coating weight per side or an Fe-Zn electroplating layer of 1 to 10 g/m2 coating weight per side having 50 to 80 wt.% Fe content is formed. This galvanizing or Fe-Zn alloy plating is executed with an ordinary sulfuric acid bath, a chloride bath or the like. In this way, the hot dip galvanized steel sheet of thick coating weight good in surface appearance can be obtd.
SUGIMOTO YOSHIHARU
IMOKAWA TORU
SAGIYAMA MASARU
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