Polysubstituted Pyrazoles as Corrosion Inhibitors for SAE 1020 Steel in 1 M HCl

Most efficient corrosion inhibitors are heterocyclic compounds containing oxygen and nitrogen atoms, which act by adsorbing onto metal surfaces and donating electron pairs. Ketene dithioacetals are important building blocks in organic synthesis and have been widely used for the preparation of diverse heterocyclic compounds. In this work, ketene dithioacetals were used to synthesize polysubstituted pyrazoles that exhibited the ability to inhibit the corrosion of SAE 1020 carbon steel in 1 mol L^-1 HCl. Theoretical calculations made it possible to correlate physicochemical properties with the different inhibition efficiencies observed experimentally and suggested that intramolecular hydrogen bonding may contribute to the differences in corrosion inhibition performance. The compound with the highest inhibition efficiency was further evaluated at different concentrations and maintained a corrosion inhibition efficiency above 90%, even at substantially lower inhibitor concentrations. Its adsorption behavior was well described by the Langmuir adsorption isotherm, indicating the coexistence of both physisorption and chemisorption on the SAE 1020 steel surface. These findings demonstrate that ketene dithioacetals provide an efficient synthetic route to functionalized pyrazoles with excellent potential as corrosion inhibitors for carbon steel in acidic media.