Sustainable corrosion mitigation of mild steel in 1 M HCl using pharmaceutical waste: The ELT approach

Expired Labetalol, a common beta-blocker, has a unique application beyond its original use: serving as an effective and sustainable corrosion inhibitor for mild steel in a 1 M HCl environment. This innovative repurposing of a discarded pharmaceutical contributes to industrial sustainability. A study using weight loss measurements found that this expired labetalol tablet (ELT) performs optimally at a concentration of 0.001 M and a temperature of 303 K. The anti-corrosion mechanism was confirmed through a variety of analyses. Thermodynamic and kinetic parameters, along with the adsorption isotherm model and FT-IR, demonstrated how the ELT system inhibits corrosion. The formation of a protective layer on the steel's surface was further verified by ac-impedance spectroscopy, SEM, EDAX, and AFM. Potentiodynamic polarisation studies revealed that ELT acts as a mixed-type inhibitor, influencing both the anodic and cathodic corrosion processes. The expired labetalol tablet (ELT) system was chosen as a corrosion inhibitor because of its several advantages. It's cost-effective and readily available, which makes it a practical choice. The system is also highly efficient at preventing corrosion. Additionally, its non-toxic and sustainable nature makes it an environmentally friendly option, aligning with modern industrial practices. Its solubility is also a key factor, ensuring it can be easily integrated into the corrosive environment. The research findings have potential applications in the pickling industry, where steel is treated with hydrochloric acid to remove rust.