Comparison of the synergistic inhibition mechanism of two eco-friendly amino acids combined corrosion inhibitors for carbon steel pipelines in oil and gas production

The combination of corrosion inhibitors is a significant method to enhance the inhibitive effects of inhibitors owing to their synergism. In this work, the inhibition synergism of two eco-friendly amino acids (L-histidine, L-cysteine) and thiourea on the corrosion of N80 carbon steel in CO2-containing environment was studied by electrochemical tests and surface analysis. The results indicate that the combination of L-histidine/L-cysteine and thiourea could synergistically boost the inhibition performance of L-histidine/L-cysteine and thiourea, i.e., present a remarkable inhibition synergism. Moreover, the synergism mechanism is in-depth revealed by theoretical calculations. The stronger interaction between L-histidine and thiourea accounts for the better synergistic inhibition effect.