Examining expired clopivas experimentally and theoretically as a corrosion inhibitor for mild steel in an acidic environment

Abstract

The repurposing of Clopivas, an expired multipart pharmaceutical drug, as a durable and efficient corrosion inhibitor for mild steel in 0.5 M H₂SO₄ is reported for the first time in this work. The use of an expired medication with several active ingredients (clopidogrel and aspirin), whose synergistic adsorption behavior improves corrosion protection and addresses pharmaceutical waste management, is what makes this work unique. Weight loss measurements, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), adsorption isotherm analysis, Fourier transform infrared spectroscopy (FTIR), and density functional theory (DFT) calculations were used to assess the corrosion inhibition performance. According to experimental findings, expired Clopivas exhibits exceptional inhibitory efficiency, surpassing 94% at 3000 ppm, with efficiency steadily increasing with inhibitor concentration. According to PDP investigations, the inhibitor suppresses both cathodic hydrogen evolution reactions and anodic metal dissolution reactions, hence functioning as a mixed-type inhibitor. The creation of a protective adsorbed coating on the mild steel surface is confirmed by the EIS results, which demonstrate a notable improvement in charge transfer resistance and improved capacitive behavior. The Langmuir isotherm is followed by the adsorption of the inhibitor, indicating monolayer adsorption. Functional groups including heteroatoms (N, O, and S) are confirmed to be involved in surface adsorption by FTIR analysis, and strong interactions between inhibitor molecules and the iron surface are supported by DFT simulations. Expired Clopivas reduces mild steel corrosion by a synergistic adsorption mechanism including both chemical and physical interactions, according to the combined experimental and computational results. This study offers a workable waste-to-value approach for corrosion protection in acidic environments by introducing expired multipart prescription medications as a novel and promising class of environmentally benign corrosion inhibitors.

Graphical abstract