The corrosion inhibition effect of two cyanothiophene derivatives, on carbon steel in an acid medium was studied using weight loss measurements, quantum chemical calculations (DFT), and scanning electron microscopy (SEM).

The inhibition efficiency of both compounds was found to increase with higher concentrations, temperature, and exposure duration. The activation energy of the corrosion inhibition reaction in the presence of the inhibitors was higher than that of the blank solution. The experimental data followed the Langmuir adsorption isotherm, and the free energy values indicated that the inhibitors were spontaneously adsorbed on the steel surface through a mixed adsorption mechanism. SEM analysis confirmed the formation of a protective organic layer on the steel surface, while DFT calculations further supported the experimental findings, demonstrating that the inhibition effect is dependent on the molecular structure of the derivatives.