EFFECT OF PASSIVATION TREATMENT AND STORING ON ADHESION AND PROTECTIVE PROPERTIES OF LACQUERED TINPLATE CANS

Tinplate cans internally coated with three commercial lacquer systems were studied. The relationship found between lacquer adhesion, metalli c chromium (CrM), chromium oxide (CrOx), and total chromium (CrT) exis ting in the passivated layer was: adhesion = CrM+10 (CrOx/CrT). The st udy was completed by conducting electrochemical impedance spectroscopy (EIS) and direct current (DC) polarization experiments up to 410 days . A dilute acetic acid-sodium chloride solution was used as electrolyt ic and a full opened can was used as the working electrode and an elec trolyte cell. Iron dissolution was determined by atomic absorption spe ctrophotometry (AAS). The EIS, DC, and AAS techniques gave similar res ults. Passivation treatment did not substantially affect the porosity results.