Synthesis and evaluation of omeprazole-based derivatives as eco-friendly corrosion inhibitors for Q235 steel in hydrochloric acid

The application of expired drugs as corrosion inhibitors is a low-cost, cost-effective and environment-friendly alternative to the expensive degradation process. Against this background, the corrosion inhibition performance and mechanism of imidazole drugs omeprazole (OMP) and its by-products omeprazole sulfide (OMP-1) and omeprazole sulfonate (OMP-2) on Q235 steel in 1 M HCl is investigated by weight loss experiment, electrochemical technology, surface analysis methods (SEM and XPS), quantum chemical calculation and molecular dynamics simulation. The results demonstrate that OMP, OMP-1 and OMP-2 are effective corrosion inhibitors for Q235 steel in 1 M HCl. The inhibition efficiency above 95% is achievable at 298 K with 0.2 mM inhibitor concentration. The test results and fitting data show that they are mixed-type corrosion inhibitors, which comply with Langmuir adsorption isotherm. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) further confirmed these three inhibitor molecules playing the role of corrosion inhibition by adsorbing on the surface of Q235 steel to form a film barrier. The corrosion inhibition mechanism of omeprazole on metal surface is also discussed.