Modeling of the corrosion process in the interaction of tinplate with vegetable canned food

Abstract

When choosing metal packaging for canned vegetables, it is advisable to take into account their corrosivity, because the inner surface corrosion is one of the factors affecting product quality during storage. To rationalize the corrosion tests of metal packaging materials, it is advisable to replace food with model media – organic acids solutions. The aim of this work was to study the corrosion kinetics of electrolytic tinplate in model media–aqueous solutions of oxalic (mass fraction 0.25–1.00%) and citric (mass fraction 0.25–1.50%) acids, as well as their compositions. The uniform corrosion rate was measured by the linear polarization resistance method, pitting corrosion–zero resistance amperometry method. The tests were carried out using the “Expert-004” corrosion-meter, according to a two-electrode scheme. For oxalic acid solutions with a mass fraction of 0.25% and 0.50% and for all citric acid solutions, the process is characterized as uniform corrosion – the pitting corrosion rates average steady values are 7–11 times less than the corresponding uniform corrosion rates values (1.52–3.93 µm/year and 17.42–26.56 µm/year, respectively). The most aggressive with respect to tinplate are oxalic acid solutions with a mass fraction of 0.25 and 0.50% and citric acid solutions with a mass fraction of 0.25 and 0.50%. On this basis, two-component solutions of the following composition were chosen: 0.25% citric acid + 0.25% oxalic acid; 0.25% citric acid + 0.50% oxalic acid; 0.50% citric acid + 0.25% oxalic acid; 0.50% citric acid + 0.50% oxalic acid. For these solutions, the process is characterized as uniform corrosion — the pitting corrosion rates average steady values are 7–10 times less than the corresponding the uniform corrosion rates values (2.04–3.85 ?m/year and 19.56–26.93 ?m/year, respectively). For two-component solutions, an additive effect is observed–the uniform and pitting corrosion rates average experimental steady values correspond to the calculated additive values. By mathematical processing of experimental data, it was found that the uniform corrosion steady rate maximum value the corresponds to a two-component solution containing 0.40% citric acid and 0.30% oxalic acid. This is confirmed by experimental data–the uniform corrosion rate average steady value for this solution is 28.18 ?m/year. According to the research results it was found that as a model corrosive medium that simulates canned vegetables, it is advisable to use a solution containing 0.40% citric acid and 0.30% oxalic acid, because it is the most aggressive.