NEW ENVIRONMENTALLY FRIENDLY COMPOSITIONS AS INHIBITORS OF METAL CORROSION

Abstract

The development of effective and safe corrosion inhibitors of metal constructions remains an urgent problem. The aim of the present study is evaluation of inhibitory action of new compositions based on synthetic and biogenic surfactants, waste glycerol (a by-product of biodiesel) and low-toxic biocides-thiosulfonates, on the corrosion of St3 steel in different concentrations of sodium chloride aqueous solutions, at various temperatures. It was shown, that at 20 °C in medium NaCl (0.1 and 1.0 wt %) the best protective properties have mixtures of biosurfactant BS-1 with Tween-80 (1:5 and 1:3, w/w) – protection degree in 0.1 % NaCl was 69 and 61 %, respectively. With temperature increased to 50 °C, the protection degree decreased to 63 and 48 %. Waste glycerol (5 g·dm-3) in 1% NaCl also proved effectiveness, increasing St3 steel protection up to 86 %. When using biosurfactants and waste glycerol, the film on the metal surface formed due to hydrogen bonds between inhibitors functional groups and iron ions probably decreased the corrosion rate of steel. Compositions of biosurfactant BS-2 with thiosulfonates TS-1, TS-2 (ratio 0.5 and 0.25 g·dm-3) at 20 °C contribute to steel protection 99 %. Thus, action synergism was observed, therefore for effective steel protection it is advisable to use additional synergists into composition. The results indicate new prospects of compositions of biosurfactants, products of biotechnology, for new "green" corrosion inhibitors.

Keywords

• biosurfactants
• corrosion inhibitors
• rhamnolipids
• thiosulfonates
• trehalose lipids
• waste glycerol.