Eco-friendly pyridine-derivatives for corrosion inhibition of carbon steel during acidic treatments: mechanistic insights from electrochemical, surface, and computational studies

Pyridine and urea derivatives have emerged as valuable corrosion platforms ascribed to exceptional coordination potential, and environmental friendliness. Two novel structures of pyridine-carbamides (MS30 & MS31) were synthesized and used as green corrosion inhibitors for the carbon steel in 1M HCl. Electrochemical measurements determined the increase in efficiency with concentrations, reaching 95.3% and 97.1% at 200 mg L-1 and 298 K for MS30 and MS31. Despite the reduced performance with increasing temperature to 303 and 313 K, results revealed improved inhibition at 323 K. At the highest temperature of 323 K, MS30 and MS31 proved their influence in maintaining 97.6% and 93.4% efficiency, highlighting their suitability for treatments in oilfield downhole regions. The adsorption of both inhibitors fitted the Langmuir model and was attributed to chemisorption, as inferred from thermodynamics. Corrosion kinetics and activation energy also verified the chemical interaction of the Fe-inhibitor complex. Spectroscopic surface evaluation interpreted the surpassed metallic dissolution by MS30 and MS31 through protective barrier formation, and X-ray photoelectron spectroscopy (XPS) determined the existence of the Fe-N bond. The sustained viability of human cells affirmed the nontoxic nature of MS30 and MS31 after treatment with 0.2 mg mL(-1) of MS30 and MS31 compounds. DFT calculations revealed that both inhibitors exhibited strong adsorption on the metal surface (-9.5 eV), classified as chemisorption. Overall, the experimental findings are well supported with surface and computational studies. These pioneering compounds are introduced herein to advance state-of-the-art inhibitors, providing high efficiency under challenging environments.