| 摘要 |
PURPOSE:To produce easily and inexpensively a blackened steel sheet having high quality by treating a steel sheet having a plating layer consisting of Ni, alloyed Ni, alloyed Co, etc. with a treating liquid contg. nitric acid then treating immediately the sheet with an aq. alkali soln. of NaOH, etc. CONSTITUTION:A plated steel sheet 1 having an Ni plating layer, alloyed Ni plating layer or alloyed Co plating layer 2 as the uppermost layer is primarily treated 3 with a treating liquid of nitric acid or mixed acids consisting essentially of nitric acid or a liquid prepd. by adding sulfate or nitrate as an additive to the mixed acids or a soln. consisting essentially of an oxidizing agent such as hypochlorous or the like. The primarily treated steel sheet is then secondarily treated 4 with an aq. alkali soln. of NaOH, KOH, Ca(OH)2, etc. in succession thereto without rinsing and thereafter the sheet is rinsed 5 to stop progression of the reaction. The treated steel sheet is dried 6. The blackened steel sheet having the blackened film 7 which has good adhesion, is dense and has no interference colors is thus obtd. |
