CHROMATE TREATED COMPOSITION FOR GALVANIZED STEEL AND CHROMATE TREATED GALVANIZED STEEL EXCELLENT IN CHROMIUM ELUTION PROPERTY AND CORROSION RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide chromate treated galvanized steel excellent in corrosion resistance and blackening resistance and also extremely little or free from the elution of haxavalent chromium which is an environmental polution substance, and to provide a chromate treated composition having industrially sufficient bath stability.;SOLUTION: This composition contains partially reduced chromic acid, a phosphoric compound and a nitric compound as essential components, and in which the relations in the following inequalities of (I) to (IV) are satisfied between the chromium reduction ratio (X) of partially reduced chromium acid and the concentration of each component in the bath: 60%≤X≤100%...(I), 0.1≤HNO3/CrO3≤1.0...(II), and, in the case of Y=(HNO3/CrO3)+(H3PO4/CrO3), Y≤0.0002 X2-0.02 X+3.1...(III) and Y≥0.0005 X2-0.05 X+2.6...(IV).;COPYRIGHT: (C)2001,JPO