Mesomorphic cyanobiphenyl appended thiols as anti-corrosive materials: Electrochemical and theoretical investigations

Cyanobiphenyls are well-known for their liquid crystalline organization. The molecules that can undergo self-assembly on the surface of metal, offer potent corrosion inhibition properties. Herein we report five such cyanobiphenyl derivatives as potential anti-corrosion films on the surface of mild steel immersed in 1M HCl medium. The electrochemical impedance measurements and potentiodynamic polarization measurements reveal that the cyanobiphenyl derivative with shortest chain length out of the five inhibitors under consideration (i.e., 4′-((6-mercaptohexyl)oxy)-[1,1′-biphenyl]-4-carbonitrile) exhibited up to 98% efficiency for the drop cast volume of 25 µL of 1 mg/mL of stock solution as compared to increased chain length molecules. The surface characterization of the corroded and protected mild steel surface was done by using a scanning electron microscope and energy-dispersive X-ray spectroscopic methods which affirms the presence of protective film on the surface of mild steel after exposure to acid medium. The theoretical calculations support experimental observations with respect to trends in the efficiency of short-chain and long-chain functionalized cyanobiphenyls.

Graphical Abstract

Five different chain-length cyanobiphenyls appended thiols as anti-corrosive materials on the surface of mild steel in an acidic medium were investigated by electrochemical, theoretical and surface characterization methods. The efficacy of the molecule was as high as 98–99% at a very small drop cast volume of 25 µL.