Sour corrosion of C1018 carbon steel and its inhibition by 1-benzylimidazole: electrochemical, SEM, FTIR and computational assessment

The sour corrosion of C1018 carbon steel in CO2-saturated 3.5% NaCl + 100 ppm H2S solution and its inhibition by a low-toxic molecule, 1-benzylimidazole (1-Benz), has been investigated. Electrochemical impedance spectroscopy (EIS) results reveal that 1-Benz can form a strongly-adsorbed and highly protective inhibitor layer on the steel surface. Potentiodynamic polarization (PDP) results confirm that 1-Benz is a mixed-type corrosion inhibitor with slightly more anodic tendency. An optimum concentration of 150 ppm provided up to 83% inhibition efficiency. Based on FTIR characterization, 1-Benz interacts with the steel surface using its nitrogen atom and C=C pi-electrons and it adsorbs following the Temkin isotherm. The adsorption reduces localized corrosion, according to SEM-EDX observations. Theoretical parameters confirm that the electron-rich imidazole N atoms and electron-deficient C atoms in the phenyl ring ensure easy electron transfer between 1-Benz and the steel surface.