Utilizing Some Indole Derivatives to Control Mild Steel Corrosion in Acidic Environments: Electrochemical and Theoretical Methods

Ethyl 3-formyl-1H-indol-2-carboxylate (FIC) and 2-(4-methoxyphenyl)-2,4-dihydropyrrolo [3,4-b]indol-3-ol (MPI) were synthesized as indole derivatives. The chemical structures of FIC and MPI were established through analytical and spectroscopic
techniques. The inhibitory impacts of FIC and MPI on mild steel (MS) in an acidic environment (0.5 M H2SO4) were investigated by employing methodologies including open
circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP). As the studied indole derivatives adsorbed on the surface of MS,
they created a barrier to mass and charge movement, shielding the MS from dangerous
ions. It was observed that the inhibitory efficiency (%EF) values increased with the molar
concentration of indole derivatives (FIC and MPI). At all concentrations, the two indole
derivatives being studied, FIC and MPI, had high efficiency values. The highest efficiencies
at 90 ppm were 81.2% with MPI and 76.2% with FIC. The polarization curves also clearly
showed that MPI and FIC function as mixed-type inhibitors. Additionally, this study used
density functional theory (DFT) and molecular dynamics (MD) simulations to investigate
how well the two indole derivatives prevented mild steel corrosion.