Corrosion in Tinplate Cans Used for Food Storage. Part 2: Characterization and Corrosion Phenomena in BPA-NI Coated Cans

Abstract

Corrosion phenomena associated with tinplate cans were investigated with aqueous solutions of different compounds commonly found in canned tomato products. After only a few weeks of storage at 49 °C, cans lined with a coating free of bisphenol A (BPA) displayed degradation of the coating. Storage of solutions containing chloride, nitrate, and thiosulfate ions in the BPA-NI coated cans resulted in extensive formation of blisters, which are attributed to cathodic delamination. Additionally, headspace blackening, which is sometimes found in packaged protein-containing foods, was also observed. Volatile sulfur-containing compounds produced during the sterilization process might be the origin of headspace blackening. In this study, the corrosion of tinplate cans exposed to different solutions at 49 °C for varying storage times was studied via optical microscopy, optical profilometry, X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The results showed a strong correlation between the presence of cysteine, an amino acid, and/or nitrate, and the degradation of the coating. Furthermore, cysteine was found to be a source of headspace blackening.