PROCESS FOR PRODUCTION OF TIN-PLATED STEEL SHEETS, TIN-PLATED STEEL SHEETS AND CHEMICAL CONVERSION TREATMENT FLUID

摘要

A chemical conversion treatment fluid which contains aluminum primary phosphate in an amount exceeding 18g/L and up to 200g/L and has a pH of 1.5 to 2.4; and a process for the production of tin-plated steel sheets which comprises forming an Sn-containing plating layer on at least one side of a steel sheet in a coating weight of 0.05 to 20g/m2 per side, subjecting the plated steel sheet either to dipping in the chemical conversion treatment fluid or to cathodic electrolysis in the chemical conversion treatment fluid at a current density of 10A/dm2 or below, and then drying the resulting steel sheet to form a chemical conversion coating.  The process involving the use of the treatment fluid can give, through low-cost chemical conversion treatment and even without using Cr causative of environmental problems, a tin-plated steel sheet wherein the surface appearance or the close adhesion of a coating is inhibited from being deteriorated by surface oxidation of the tin plating layer.