Evaluation of Interaction of Lacquer Coated Cans with Melon Cubes by Electrochemical and Other Methods

Abstract

Electrochemical measurements, visual appearance and estimation of dissolved iron were applied in order to assess the performance of lacquered tinplate cans filled with melon cubes and stored at 15,25,35 and 45°c. Visual appearance rating was found to relate well with polarisation resistance, indicating for a heavily attacked can a low visual score and a low resistance value. Corrosion potential values of the lacquered cans changed little with change in storage time and temperature, apparently due to the small dissolved metal concentration in this product. Corrosion currents, as obtained from potentiodynamic measurements, were found to increase linearly with time, and Q₁₀ values of about 1·8 were calculated for the metal exposure rate. An equation relating current density with time and temperature, which enables the prediction of shelflife of the food-lacquered can system, was found. Corrosion currents obtained from linear polarisation and potentiodynamic measurements were found to be related, indicating that linear polarisation, which is a fast and simple method, may be used for estimating corrosion currents. A relationship between current density and dissolved iron was also found and either or both of these values can be used as a criterion for the shelflife of the product itself.