A thermodynamical, electrochemical and surface investigation of Bis (indolyl) methanes as Green corrosion inhibitors for mild steel in 1Â M hydrochloric acid solution

The influence of three Bis (indolyl) methanes (BIMs) namely, 3,3′-((4-nitrophenyl) methylene) bis (1H-indole) (BIM-1), 3,3′-(phenyl methylene) bis (1H-indole) (BIM-2) and 4-((1H-indol-2-yl)(1H-indol-3-yl) methyl) phenol (BIM-3) on the mild steel corrosion in 1 M HCl was studied by weight loss, electrochemical, scanning electron microscopy (SEM), and dispersive X-ray spectroscopy (EDX) methods. Results showed that BIM-3 shows maximum inhibition efficiency of 98.06% at 200 mg L−1 concentration. Polarization study revealed that the BIMs act as mixed type inhibitors. Adsorption of BIMs on the mild steel surface obeyed the Langmuir adsorption isotherm. The weight loss and electrochemical results were well supported by SEM and EDX studies.