Electrochemistry at steel/ acid interface: Adsorption and corrosion inhibition effect of chemically modified expired amantadine drug

Development of environmentally sustainable corrosion inhibitors for alloy steels is a major industrial challenge. Considering the huge costs involved for exploration, design and synthesis of novel organic molecules, the use of left-over or expired drugs could provide a suitable alternative. Herein, grinding-assisted microwave is used with 4-nitrobenzaldehyde to chemically functionalized expired amantadine (AD) in one step. Green chemistry metrics to the synthesis are illustrated. AD-NPMI, a Schiff base compound, inhibited mild steel corrosion in 1 M HCl. The expired medication and Schiff base had highest inhibitory efficiency of 92.61% and 97.71% for AD and AD-NPMI at 500 mg L −1 . Results showed that increasing inhibitory concentration increased corrosion inhibition efficiency. Gravimetric studies demonstrated high efficiencies of >95% even at elevated temperatures. EIS studies showed charge transfer control of the electrochemical process, while PDP experiments showed a mixed inhibitor effect with anodic behavior. EIS and PDP supported that the synthesized Schiff base provided a superior inhibition compared to the unmodified drug. Schiff base adsorption on mild steel surface inhibited corrosion using the Langmuir model by mixed physical and chemical adsorption. DFT calculations showed that protonated inhibitors strongly adsorb on metal surfaces. Schiff base inhibitors adsorb better on metallic surfaces than parent molecules. Results indicate that developed formulations can reduce corrosion during industrial pickling. This work provides a potential alternative to costly and toxic corrosion inhibitors conventionally used in the industries. • Schiff baseof expired drug amantadine prepared synthesized using 4-nitrobenzaldehyde. • Green Chemistry aspects to the synthesis evaluated. • A novel and green techniques of grinding-assisted microwave irradiation. • Schiff basewas tested as inhibitors for corrosion of mild steel in 1H HCl at various temperatures. • High inhibition of ~95% was obtained with a mixed type behavior and anodic predominance.

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