Developing two amino acid derivatives as high-efficient corrosion inhibitors for carbon steel in the CO2-containing environment

Abstract

During the oil and gas exploitation, the corrosion of carbon steel pipes causes great economic loss, heavy casualties, environmental pollution, and waste of resources. The development of highly efficient and stable corrosion inhibitors is of great significance for the corrosion protection of carbon steel in oil and gas exploitation. L-cysteine is widespread in various plants (e.g. onion, cauliflower, and cabbage sprout). As a corrosion inhibitor, it usually has low inhibitive efficiency in most corrosive environment. Chemical modification is the most efficient method to solve this issue. Herein, two synthetic amino acid derivatives (2-phenylthiazolidine-4-carboxylic acid (PTCA) and 2-(thiophen-2-yl)thiazolidine-4-carboxylic acid (TTCA)) were investigated as high-efficient corrosion inhibitors to deal with the corrosion issue of carbon steel in the CO2-containing environment. The anti-corrosion property of the amino acid derivatives was investigated by electrochemical experiment, surface technique and theoretical calculations. The electrochemical results show that PTCA and TTCA present high corrosion inhibition efficiencies at the concentration of 0.8 mM: PTCA (99.1%) and TTCA (99.3%). The inhibitive mechanism of PTCA and TTCA on carbon steel surface is revealed by theoretical calculations. It is found that the PTCA and TTCA adsorb at the steel/solution interface by forming Fe-O bonds. Compared to PTCA, TTCA exhibits stronger adsorption on carbon steel surface by forming shorter Fe-O bonds with a more negative adsorption energy, which accounts for the better inhibitive performance of TTCA.