Influence of the lacquer and end lining compound on the shelf life of the steel beverage can

Beverage cans, made from tinplate, need to be applied with double spray lacquering as coating to avoid iron pick-up. This work aims to evaluate the influence of two different lacquer systems (internal can area) and two different sealant compound systems during the end seaming operation (can closing) on the iron pick-up from the steel beverage can after storage with a cola soft drink. Analyses of iron pick-up and measurements of electrochemical impedance, during the period of storage of the cans were carried out. The experiments were undertaken with the cans in the normal position during 6 months at 37 °C. A full opened can with electrolyte was used as the working electrode and electrolytic cell. Scanning electron microscopy (SEM) was also carried out on the surface of the tinplate and cup, before and after the draw and wall ironing (DWI) process. The electrochemical impedance spectroscopy (EIS) and atomic absorption spectroscopy (AAS) results show the optimal system (lacquer/compound) to be used as coating for steel beverage can. The SEM images revealed areas of exposed iron on the surface of the cup formed after DWI process.