Smudge on tinplate steel sheets and the effects of cathodic dichromate treatment

Smudge is black granules that scatter on tinplate sheet; it was formed during the process of plating and storing, and seriously affected the function and appearance of tinplate sheet. Reflowing and cathodic dichromate treatment (CDC) are two major phases in which smudge is produced. In this paper, the appearance and component of smudge was analyzed by means of whiteness meter, SEM and EDS quantitatively. Factors of CDC conditions was studied. Results of tests showed that whiteness measurement is convenient to evaluation of the degree of smudge and the effects of CDC on it , quantitatively.