PRODUCTION OF TIN-FREE STEEL PLATE

PURPOSE:To obtain a Cr film which has a uniform film construction and good retort resistance in the stage of applying an electrolytic chromic acid treatment on a steel plate by subjecting the steel plate to the 1st electrolytic chromic acid treatment contg. a simple salt type fluoride as an assistan...

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Hauptverfasser: TSUGAWA SHIYUNICHI, ICHIDA TOSHIROU, HARADA SHIYUNICHI, KOBAYASHI HIDEO, OGATA HAJIME
Format: Patent
Sprache:eng
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Zusammenfassung:PURPOSE:To obtain a Cr film which has a uniform film construction and good retort resistance in the stage of applying an electrolytic chromic acid treatment on a steel plate by subjecting the steel plate to the 1st electrolytic chromic acid treatment contg. a simple salt type fluoride as an assistant and to the 2nd electrolytic chromic acid treatment contg. a complex salt type fluoride as an assistant. CONSTITUTION:Cr plating is applied on a steel plate in a Cr plating bath, whereafter the steel plate is reverse electrolyzed in the Cr plating bath to elute a part of the hydrated oxide film of Cr formed in the stage of the Cr plating and the anions of the assistant codeposited on the hydrated oxide film of Cr. The steel plate is then thoroughly washed in an aqueous washing bath. Further, the steel plate is subjected to the 1st electrolytic chromic acid treatment in an aq. chromic acid treatment bath contg. chromic anhydride and a compd. of >=1 kind of chromate and dichromate as a base component and a simple salt type fluoride as an assistant. The treated steel plate is subjected to the 2nd electrolytic chromic acid treatment in an aq. chromic acid soln. contg. a complex salt type fluoride as an assistant.