| CPC C23F 1/28 (2013.01) | 18 Claims |

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1. A roughening treatment method for roughening a surface of stainless steel, the method comprising:
roughening the surface of the stainless steel that contains copper or a metal having an ionization tendency larger than copper by contacting a first aqueous composition with the surface of the stainless steel in a roughening treatment, and
performing a post-treatment by contacting, under an acidic condition, a second aqueous composition comprising a peroxide with the surface of the stainless steel that has been roughened in the roughening treatment,
wherein the first aqueous composition comprises, based on a total amount of the first aqueous composition:
0.1% to 20% by mass of hydrogen peroxide;
0.25% to 40% by mass of copper ions; and
1% to 30% by mass of halide ions.
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