| 摘要 |
PURPOSE:To produce an electrogalvanized steel sheet having excellent corrosion resistance by subjecting a steel sheet to a cathodic electrolytic treatment in an electrogalvanizing bath added with a small amt. of Mg ions after degreasing and pickling. CONSTITUTION:The steel sheet is subjected to pretreatments such degreasing and pickling, then to the cathodic electrolytic treatment in the electrogalvanizing bath added with the Mo ions. The above-mentioned electrogalvanizing bath is the bath which contains zinc as an essential component and is added with elements such as Cr and Ni in addition to a pure galvanizing bath, for which a sulfuric acid system essentially consisting of, for example, ZnSO4 and chloride system essentially consisting of ZnCl2 are used. On the other hand, MgSO4, etc., are adequate for the sulfuric acid bath and soluble Mg compds. such as MgCl2 are adequate for the chloride bath as the above-mentioned Mg ion source. Such source is added at preferably about 0.02-10g/l. The electrogalvanized steel sheet having the excellent corrosion resistance is obtd. by the above-mentioned plating treatment and thereafter, the steel sheet is subjected to post treatments including oil coating, chromate treatment, electrolytic chromate treatment, phosphate treatment, etc., as necessary, by which the plated steel sheet product is obtd.
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