Inhibition of the corrosion of carbon steel in hydrochloric acid solution by bisquaternary ammonium salt

The effectiveness of bisquaternary ammonium salt N,N′‐Bis(dodecyldimethyl)‐3‐oxa‐1,5‐ pentanediammonium dichloride used as corrosion inhibitor for carbon steel in 1.0 M HCl was investigated by weight loss and electrochemical techniques. Surfaces were characterised by scanning electron microscopy. The performance of the bisquaternary ammonium salt was also compared with that of urotropine, a commercial corrosion inhibitor for acid media in industry practice. The results showed good inhibiting action of the inhibitor. The inhibition efficiency increases with the inhibitor concentration but is temperature–independent. N,N′‐Bis(dodecyldimethyl)‐3‐oxa‐1,5‐pentanediammonium dichloride acts mainly as a mixed‐type inhibitor. The inhibition of this bisquaternary ammonium compound was assumed to occur via adsorption of the inhibitor molecule on the metal surface without affecting the corrosion mechanisms. The adsorption of the inhibitor on the metal surface in HCl solution was found to obey Frumkin's isotherm.