Corrosion inhibition of carbon steel in hydrochloric acid by organic compounds containing heteroatoms

Abstract Three organic inhibitors containing heteroatoms, namely: undecenoic acid hydrazide (UAH); 2-mercaptobenzothiazole (MBT); and 2-hydrazinobenzothiazole (HBT) have been synthesised in the lab and their inhibiting action on the corrosion of carbon steel in 1N HCl was investigated by means of two different techniques, namely weight loss and potentiodynamic studies. The weight loss studies were conducted in 1MHCl at different temperatures (30, 45, and 60°C) using various concentrations (25–500 ppm) of the inhibitor, and the inhibitor with the highest efficiency (HBT) was also tested for different immersion times (1/2, 3, 6, and 24 h) at the optimum concentration (500 ppm) at room temperature (30°C). The results show that the inhibitor efficiency increases with increased temperature, from room temperature (30°C) to 60°C at the most effective concentration (500 ppm). Inhibitor efficiency (IE) also increases with increase in the inhibitor concentration from 25 to 500 ppm at a given temperature and time. The effect of immersion time on the inhibition efficiency (IE) for HBT was also studied, and the results show that the inhibition efficiency (IE) increases with immersion time. The potentiodynamic polarisation studies revealed that UAH is a mixed type of inhibitor whereas MBT and H BT are predominantly anodic inhibitors. The adsorption of these inhibitors on the metal surface obeys the Temkin adsorption isotherm.