Abstract
Tinplate has been widely used for can container. However, as the can manufacturing method had been rapidly changed from soldered can to welded can, superior lacquer adhesion was strongly required to manufacture lacquered can body and can end.
A study about the cathodic treatment in the chromic acid and sulfuric ion bath was carried out to improve the lacquer adhesion of tinplate. It revealed the following facts:
The cathodic treatment greatly improves the lacquer adhesion of tinplate when the chromium coating weight exceeds 20mg/m2.
This fact results from the increase of chromate layer coverage on the tinplate surface, which was quantitatively measured by CMA mapping method.
As for the structure of chromate layer, the deposition of metallic chromium inside is essential to suppress the growth of tin oxide.
