Evaluation of Corrosion Inhibitors Synthesized from Fatty Acids and Fatty Alcohols Isolated from Sugar Cane Wax Available to Purchase

Saturated waxy fatty acids (WFAc, 3b) and waxy fatty alcohols (WFAl, 4) were isolated from sugar cane wax. The former were used for the synthesis of the corrosion inhibitors 1-(2-aminoethyl)-(1c) and 1-(2-hydroxyethyl)-2-alkyl-2-imidazolines (1d), and the later were used to prepare waxy phosphate esters (WPE, 6). The inhibiting action of compounds 1c and 1d on carbon steel corrosion, using 1 M hydrochloric acid (HCl) and hydrogen sulfide brine as corroding solutions, was evaluated by the weight-loss method and polarization techniques. In order to know the effect of the alkyl chain length on the inhibition efficiency (IE), compounds 1c and 1d were compared with the structurally analogous imidazolines (1a and 1b), which were obtained from the commercially available fatty acids tall-oil (3a). The imidazolines 1c and 1d showed outstanding IE and low corrosion rate (CR) at 250 ppm. Imidazoline 1d showed a synergic effect with the addition of 6.