Corrosion studies of tinplate cans by means of electrochemical techniques

Abstract

The suitability of electrochemical techniques for the evaluation of food can corrosion was studied. The electrochemical measurements were carried out using three experimental systems: (1) The open filled can as both the working electrode and the electrolytic cell; (2) electrolytic cell of double electrode developed specifically to measure the corrosion resistance of tinplate – Massini’s cell, which has been modified by introducing a reference electrode; (3) ASTM cell modified to test tinplate samples. Plain tinplate food cans and lacquered ones filled with a model solution were studied. The determination of corrosion current and cathodic Tafel slope for the lacquered cans as both electrolytic cell and working electrode and for samples from plain tinplate cans is the modified Massini’s cell was possible by using the Large Potential Approximation Method conjugated with a theoretical method to compensate the IR-drop of these systems. The electrochemical parameters obtained for the lacquered cans were very consistent, and the corrosion current was in good agreement with the concentration of iron and tin dissolved during shelf life studies. Regarding the plain tinplate cans and the ASTM cell the Large Potential Approximation Method could not be used mainly due to the ratio between the exposed areas of tin iron, wich cause the oxygen reduction as the main cathodic reaction in the large of the applied potential, thus occurring concentration polarization. The tests carried out with the modified Massini’s cell and samples from plain tinplate cans did not lead to consistent results.


Reference
FARIA, E.V.; KAJIMOTO, Z.P.; SILVA, R.D.; DANTAS, S.T.; NISIDA, A.L.A.C., Ensaios para avaliação da corrosão de folhas-de-flandres para latas de alimentos. In:INTERNATIONAL CONGRESS FOR SURFACE FINISHING, 1992, São Paulo. Anais… São Paulo: ABTS, 1992. v. 2, p. 921-938. (IPT Publicação, 2114)

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