Corrosion inhibition with different protective layers in tinplate cans for food preservation.

Background: In this work the influence of essential onion oil (EOO) on the protection of tinplates was compared with dioctyl sebacate oil (DOS) and epoxy phenolic lacquers, which are frequently used in the food canning industry.

Results: When EOO as the protective layer instead of DOS oil was used, tinplate porosity, measured electrochemically (7.58 ± 1.97 µA cm(-2) and 23.0 ± 1.3 µA cm(-2), respectively), and iron coating mass, calculated from AAS data (1.52 ± 0.15 mg m(-2) and 3.14 ± 0.42, respectively), was much lower indicating better corrosion protection. At higher storing temperature (36 °C) the addition of EOO to canned tomato purée enhanced the formation of hydrogen with time. The increasing volume fraction of H(2) (from 34.0 to 90.9% for cans without nitrates, and from 33.8 to 89.2% for cans with nitrates) is an indicator that corrosion takes place.

Conclusion: As the use of EOO improves the protection of tinplate compared with DOS oil, and is almost as effective as epoxy phenolic lacquer, the addition of EOO can be recommended due to lower cost of canned food production and enhanced organoleptic properties, but the storage temperature has to be lower then 36 °C.