Abstract
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•Eco-friendly and cost effective disposal of expired drug.•The studied inhibitors were synthesized from expired isoniazid.•They controlled the rate of corrosion by adsorbing on the mild steel surface.•Their adsorption was investigated by XPS and IR spectrum.•All the experimental results showed good agreement with DFT and MD study.
The severity of the problem of corrosion led Corrosion Scientists to do extensive work to find out a solution which can minimize the damage caused by corrosion. In this context corrosion inhibitors, has been offered a very promising solution for acidic corrosion. In view of it, some Schiff bases of Isoniazid with 5-substitute indole derivatives were synthesized and investigated for their corrosion hampering potential. The spectral characterizations (Fourier-Transform Infra-Red, 1H Nuclear Magnetic Resonance, elemental determination, i.e. CHN) were done to ensure their synthesis. This study reported results obtained from electrochemical impedance spectroscopy (EIS), polarization measurement, and weight loss, scanning electron microscopy equipped with energy dispersive x-ray analysis (SEM-EDX), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The experimental results were excellently complemented with the results obtained from density functional theory, i.e. DFT and molecular dynamics, i.e. MD. These hydrazones inhibited corrosion by adsorbing themselves on the metal surface which was confirmed by SEM-EDX and XPS results. All the synthesized inhibitors showed appreciable efficiency (> 90%) against corrosion of mild steel in 1 M HCl medium. The activation energy increased by the presence of inhibitors (76.1, 79.8, 77.3, and 67.0 kJ mol−1 for IICH, ICCH, IBCH, and IMCH respectively) compared to that in 1 M HCl solution only (32.8 kJ mol−1). All these compounds were found to act as a mixed type of inhibitor as confirmed by shifting range of corrosion potential (30 mV, 35 mV, 18 mV, and 36 mV for IICH, ICCH, IBCH, and IMCH respectively).