| 摘要 |
PURPOSE:To obtain a satisfactory blackened steel sheet by applying an anodic treatment to the steel sheet having an Ni alloy plated layer contg. Ni of a specified quantity or more as the uppermost layer, under a specified condition in a bath contg. the specified quantity of NO<->3 ion. CONSTITUTION:The steel sheet as a material to be treated, has the Ni alloy plated layer contg. >=5wt% Ni (especially >=8wt%) as the uppermost layer. The steel sheet is treated electrolytically by using the plated sheet as an anode under the condition of 10-800coulomb/cm<2> electrical quantity, in the bath contg. 3-500g/L No3<-> ion. If >= one kind amond SO4<2->, Cl<->, Br<->, F<->, CN<->, PO4<3->, as anion are further added into the bath by 5-300g/L in total, blackened degree is further increased. It is further desirable to form a chromate film having 5-200mg/m<2> expressed in terms of Cr quantity and an organic resin film having 0.2-4mu thickness on the plated layer surface blackening treated.
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