STEEL SHEET PLATED ON ONE SURFACE AND HAVING EXCELLENT CHEMICAL CONVERTIBILITY AND ITS PRODUCTION

摘要

PURPOSE:To provide a steel sheet having an unplated surface with which an excellent chemical conversion treatment is easily accomplished by specifying respectively the amt. of the oxide film on the unplated surface of the steel sheet subjected to electroplating on one surface and the automatic reducing time thereof. CONSTITUTION:The unplated surface (surface S) of a steel sheet which is electroplated on one surface is subjected to an anodic electrolysis and is then subjected to a cathodic electrolytic reduction treatment in the region of 1-120A/ dm<2> current density and 0.5-150C/dm<2> quantity of electricity. The same bath used for the anodic electrolysis treatment may be used for the treating bath in this case and the similar result is obtd. with all the treatments as far as conductive liquids contg. NO2SO4, Na2CO3, etc. are used. The pH of the bath is preferably in a neutral region of 4-10. The amt. of the oxide film on the surface S obtd. by the treatment is 0.05-4.0mC/cm<2> and the automatic reduction time is 1.0-200sec. The excellent chemically converted film is stably obtd. on the surface S with any kind of steel and in any chemical converting bath according to the above-described method.