Evaluation of prolonged exposure of lacquered tinplate cans to a citrate buffer solution using electrochemical techniques

Abstract Four lots of tinplate cans, internally coated with water- and organic solvent-based epoxyphenolic lacquer, were studied. A 0.1 M citric-citrate test buffer solution (pH 3.5) was packed at 90 °C, sterilised at 121 °C and stored at room temperature. A full opened can was used as the working electrode and electrolytic cell. Electrochemical a.c. and d.c. experiments were conducted after different time periods up to 280 days. The dissolution of tin and iron was determined by atomic absorption analysis up to 365 days. Lot C, whose lacquering was the thickest and the least porous, showed the greatest corrosion resistance to the citrate solution. Excellent agreement was obtained between the three experimental techniques utilized. The electrochemical impedance spectroscopy method supplies accurate information on the behaviour of the tinplate-lacquer-electrolyte system.