A rapid electrochemical test for the assessment of the delamination of lacquered tinplate*

Abstract

External cathodic polarization of lacquered tinplate specimens immersed in solutions of different organic acid anion types and pH was employed to study the delamination produced around a deliberately introduced defect in the coating. Attempts were made to utilize this technique as the basis for a rapid, simple and reproducible method for the evaluation and prediction of the suitability of lacquered tinplate samples exposed to different food media. Results of experiments conducted with three types of lacquers on tinplate in citric, malic, oxalic, tartaric, fumaric, lactic and acetic acids at pH's ranging from 2.5 to 6.0, showed good reproducibility as well as good agreement with results from an accelerated immersion test and with those from actual cases of canned foods.

A tentative evaluation of the potentiokinetic polarization technique in studies of localized corrosion of lacquered tinplate

“…In the past decade much work has been expended by many laboratories on devising rapid corrosion tests employing electrometric methods in an effort to obtain more information about the mechanism of protection of metals by organic coatings, to select materials best suited to particular cases as well as to avoid the very long exposure periods needed in direct tests. General techniques used have included the measurement of potential-current and potential-time relationship (Wormwell & Brasher, 1949;Pourbaix, 1965), polarization resistance measurements (Bird, Jones & Warner, 197 1 ;Kleniewski, 1975), cathodic polarization of scratched lacquered specimens (Gonzalez, Josephic & Oriani, 1974;Albu-Yaron, Semel & Berzin, 1977) related to passivation film characteristics (Sherlock, 1976) or measurements of the coating impedance of a polymer coated steel as a function of time and coating thickness (Kending & Leidheiser Jr. 1976). Wolstenholme (1 973) reviewed and summarized most of the work done between 1936-70 with comments on some special problems associated with electrochemical measurements on painted steel.…”