N-methyl-2-hydroxyethylammonium oleate ionic liquid performance as corrosion inhibitor for mild steel in hydrochloric acid medium

The aim of the present study is to evaluate the performance of N-methyl-2-hydroxyethylammonium oleate ([m-2HEA][Ol]) as a corrosion inhibitor for mild steel in a 0.1-mol/L hydrochloric acid solution and also investigate the role of chloride in the inhibition mechanism. This protic ionic liquid (PIL) has formerly shown a high efficiency as a corrosion inhibitor in a neutral chloride medium. Electrochemical and weight loss measurements, surface contact angle determination, scanning electron microscopy, and Raman spectroscopy were used to understand the factors that influence the response of the studied inhibitor. Results revealed that [m-2HEA][Ol] behaves as a mixed-type adsorption inhibitor, by blocking cathodic sites and by modifying the activation energy of the anodic reaction, and it can reach up to 94-97% of inhibition efficiency. PIL adsorption was enhanced by the excess of positive charge of the mild steel. The effect of inhibitor molecule has been discussed to propose a mechanism that explains the inhibitory action of the corrosion inhibitor, pointing out the role of chloride in the inhibition mechanism.