EVALUATION OF PROLONGED EXPOSURE OF LACQUERED TINPLATE CANS TO A CITRATE BUFFER SOLUTION USING ELECTROCHEMICAL TECHNIQUES

Four lots of tinplate cans, internally coated with water- and organic solvent-based epoxyphenolic lacquer, were studied. A 0.1 M citric-citr ate test buffer solution (pH 3.5) was packed at 90 degrees C, sterilis ed at 121 degrees C and stored at room temperature. A full opened can was used as the working electrode and electrolytic cell. Electrochemic al a.c. and d.c. experiments were conducted after different time perio ds up to 280 days. The dissolution of tin and iron was determined by a tomic absorption analysis up to 365 days. Lot C, whose lacquering was the thickest and the least porous, showed the greatest corrosion resis tance to the citrate solution. Excellent agreement was obtained betwee n the three experimental techniques utilized, The electrochemical impe dance spectroscopy method supplies accurate information on the behavio ur of the tinplate-lacquer-electrolyte system. (C) 1997 Elsevier Scien ce S.A.