Experimental and theoretical investigation on corrosion inhibition of hexamethylenetetramine [HMT] for mild steel in acidic solution

This paper employs gravimetric, potentiodynamic polarization and SEM methods to study the corrosion inhibition of mild steel in 1 M solution of hydrochloric acid using hexamethylenetetramine as an inhibitor. The results show that inhibition efficiency increases with concentration up to 86% at 0.8 g L-1 inhibitor dosage. The data obtain are consistent with the isotherm proposed by Langmuir. The values of both activation and Gibbs free energy show that adsorption is physisorption and spontaneous. DFT quantum calculations also support a physisorption process which validates that nitrogen atoms are the most reactive and nucleophilic atoms, which is consistent with the experimental results. (C) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.