A PASSIVATION PROCESS OF A STEEL TINPLATE, PASSIVATED TINPLATE AND COATED PASSIVATED TINPLATE

摘要

The present invention relates to a process for passivating a tinplate comprising the following steps: a. subjecting the tinplate to at least one cathodic electrolytic treatment in an aqueous solution containing at least one sulphate of an alkali metal to form a tin oxide surface layer having a thickness of less than 6 mC/cm2; b. subjecting the tinplate from step a to at least one cathodic electrolytic treatment in an aqueous solution containing at least sulphate ions and zirconium ions to form a passivation layer containing zirconium on said tin oxide surface layer, the amount of zirconium in the passivation layer being 12 mg/m2 at most; c. subjecting the passivated tinplate from step b to an oxidation treatment to form an oxidized passivation layer, said oxidation treatment comprising at least one step selected from: c1. contacting the tinplate with an aqueous oxidising solution; c2. subjecting the tinplate to an anodic electrolytic treatment.