Sage extract as potential tinplate corrosion inhibitor

Tinplate is one of the most common materials in food packaging. Acidic or alkaline effects of such products cause corrosion, but also loss of their organoleptic characteristics. In recent years, due to the growing interest and attention of the world towards environmental problems and towards the protection of the environment, therefore synthetic and toxic inhibitors that are widely used in industrial processes should be replaced with new environment-friendly inhibitors. The sage (Salvia officinalis L.) is rich in biologically active compounds, especially polyphenols, and represent a potential source of, so-called, green inhibitors. Sage leaves were extracted with 30 % ethanol and high hydrostatic pressure (HHP) under operating pressure of 600 MPa and temperature 60 °C for 300 s. The inhibition efficiencies of sage extract calculated from electrochemical impedance spectroscopy (EIS). The measurement was carried out in 3 % sodium chloride solution at 25 °C in presence and absence in different concentrations (0.2 – 2.0 g/L) of sage extract. EIS techniques have shown that sage extract acts as a good inhibitor (93 %), at temperature 25 °C, and concentration of 0.6 g/L. This results confirm that sage extract exhibits good inhibitive performance for tinplate in 3 % NaCl solution, and it is more efficient to inhibit the corrosion of tinplate at the addition of 0.6 g/L than higher concentrations of sage extract. The results of ATR – FTIR analysis of the hydrophobic film modified on the tinplate surface after exposure to the 3 % NaCl solution with additions of 0.6 g/L sage extract was utilised to confirm the presence of some functional groups with O, N and S atoms adsorbed on tinplate surface. Sage extracts present good inhibition properties for tinplate corrosion because of their chemical composition and their high share of phenolic compounds whose attachment to adsorption sites on tinplate surface is responsible for the inhibition process. Modern green extraction techniques, HHP tend to be eco - friendly in terms of polyphenols extraction efficiencies from plants. Thinking long-term, the results of this research could facilitate the development of new products, by implementing plant extracts in the alkaline medium during tinplate food packaging or tinplate coating, which would reduce or completely replace the use of synthetic solutions.