METHOD OF PRODUCING TIN-FREE STEEL SHEETS HAVING IMPROVED RESISTANCE TO RETORTING TREATMENT

摘要

Tin-free steel sheets exhibiting improved retorting resistance with respect to paint adhesion are produced by chromium plating a steel sheet through cathodic electrolysis in a chromium ion-containing solution, reversely electrolyzing the sheet by a successive anodizing treatment in said solution, and subjecting the sheet to an electrolytic treatment in an aqueous chromate solution. The SO4-- concentration of the chromate solution used in the electrolytic chromate treatment should be limited to the range of 0.01 to 0.10 gram per liter of the solution.