New Hydroxylated Cationic Gemini Surfactants as Effective Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Medium

Inhibitory action of hydroxylated cationic gemini surfactants on corrosion of mild steel [MS] in 1 M hydrochloric acid medium is studied by gravimetric, electrochemical polarization and electrochemical impedance spectroscopic (EIS) techniques. The results obtained reveal that these compounds are very efficient inhibitors. The inhibitory action of surfactants increases with the concentration and chain length. Concentration as low as 10−5 M of 16–4–16 MEA could show 99% inhibition whereas 12–4–12 MEA showed 93% inhibition at 10−4 M concentration. The inhibition efficiency versus concentration curves show an S-shape plot indicating adsorption of surfactants on metal surface as a three steps process. From Arrhenius plots corrosion rate of MS was observed to decrease at any given temperature with inhibitor concentration due to the increase in the degree of surface coverage. In contrast, at constant inhibitor concentration, the corrosion rate increases with temperature. EIS measurements show increase in the charge transfer resistance with the inhibitor concentration.