Corrosion inhibition of API X120 steel in a highly aggressive medium using stearamidopropyl dimethylamine

Abstract

The inhibition efficiency of the stearamidopropyl dimethylamine (SAPDA) surfactant for the corrosion of API X120 steel in a 0.5 M HCl solution at different temperatures was investigated using different electrochemical and microscopy techniques. The kinetics and thermodynamic parameters were discussed. The overall results showed that SAPDA significantly decreased the corrosion rate of API X120 steel with an inhibition efficiency of approximately 99% at an inhibitor concentration of 136 μmol L− 1. It was revealed that the adsorption of the SAPDA surfactant on the API X120 steel surface followed Langmuir's adsorption isotherm. Polarization studies indicated that SAPDA is chemi/physisorbed on the steel surface. Quantum chemical calculations, using the density functional theory, were applied to better understand the relationship between the inhibitor efficiency and its molecular structure.