| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for descaling a metallic strip using an electrolyte or treating liquid not containing a nitric acid. SOLUTION: The metallic strip S containing any of Fe, In, Ti and Cu as an essential component into the aqueous electrolyte L containing a hydrofluoric acid and sulfuric acid. An electric current is supplied between an electronic 43 and metallic strip S immersed into the aqueous electrolyte L through the aqueous electrolyte L while the polarity of the electrode 43 is inverted at prescribed periods, by which an electrolytic descaling process step is performed. Hydrogen peroxide water is continuously or intermittently added to an immersion treating liquid of 30 to 70 deg.C containing 25 to 250 g/L sulfuric acid, 1 to 25 g/L hydrochloric acid, 1 to 50 g/L hydrofluoric acid and >=5 g/L Fe<3+> ions and simultaneously air is continuously blown at >=10 m<3> /hr/m<3> into the immersion treating liquid. As a result, an immersion descaling process step of immersing the metallic strip S into the immersion treating liquid maintained of the Fe<3+> ions in the immersion treating liquid at 5 g/L is performed.
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