Corrosion inhibition properties of polyepoxysuccinic acid derivatives in acid media

Polyepoxysuccinic acid (PESA), as a green scale inhibitor, has good scale inhibition, but its corrosion inhibition is not so good. In order to enhance its corrosion inhibition ability, PESA was modified with L-cysteine and taurine as modifiers to obtain a polyepoxysuccinic acid derivative(PESA-Lcy-Sea). The structure of PESA-Lcy-Sea was characterized by infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance spectroscopy (NMR). The thermal stability of PESA-Lcy-Sea was studied by thermogravimetric analysis(TGA), the corrosion inhibition performance of PESA-Lcy-Sea was investigated by weight loss method and electrochemical method, and the morphology and surface changes of Q235 carbon steel samples after adding PESA-Lcy-Sea were analyzed by SEM and contact angle. The results showed that PESA-Lcy-Sea had the structural functional groups of PESA, L-cysteine and taurine, which was successfully synthesized and had good thermal stability. PESA-Lcy-Sea had good corrosion inhibition on Q235 steel in 0.5 mol/L HCl solution, and the highest corrosion inhibition rate could reach 81.23% when the dosage was 400 mg/L. The adsorption of PESA-Lcy-Sea molecules on the surface of carbon steel conformed to the Langmuir adsorption isotherm. The polarization curve proved that PESA-Lcy-Sea was a mixed corrosion inhibitor. SEM and contact angle analysis of the steel surface proved that a protective film was formed on the surface by PESA-Lcy-Sea, which effectively slowed down the corrosion of Q235 steel in acid solution.