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Abstract

A process of pickling surfaces of a steel-based metallic material containing iron, carbon and chromium at a high speed wherein the surfaces of the metallic material are pickled at a high speed by dipping and then pickling the surfaces of the metallic material in an aqueous solution of hydrochloric acid or an aqueous solution of hydrochloric acid-nitric acid mixture while at least one kind of ion selected from a group comprising a platinum ion, a palladium ion and a rhodium ion is contained in a hydrochloric acid having a temperature of 50.degree. to 110.degree. C. and a concentration of 100 to 450 g/l with NO.sub.3.sup.- ion contained therein by a quantity of 300 g/l or less, as desired, or pickling treatment in the aforementioned aqueous solution by feeding a direct current between two electrodes at an electric current density of 5 to 200 A/Dm.sup.2, one of the electrodes being an anode composed of the metallic material and the other one being a cathode electrode disposed opposite to the anode, or an anode and a cathode comprising one pair of electrode plates disposed at both sides of a surface of the metallic in the aqueous solution, and feeding a direct current between the anode and the cathode at an electric current density of 5 to 200 A/Dm.sup.2, to thereby dissolve off a scale formed on the surface of the metallic material in the aqueous solution by an indirect feeding of the direct current.

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