Inhibition Effect of N-(Pyridin-2-yl-Carbamothioyl) Benzamide on the Corrosion of C-Steel in Sulfuric Acid Solutions

N-(Pyridin-2-yl-carbamothioyl)benzamide (PCMB) was newly synthesized and tested as a corrosion inhibitor for C-steel in 0.5 M H2SO4 using chemical and electrochemical techniques. Polarization measurements showed that the synthesized compound acted as a mixed inhibitor. The inhibition efficiencies obtained from the different methods were in good agreement. The inhibitive action of this compound is discussed in terms of blocking the electrode surface by adsorption of the inhibitor according to the Langmuir isotherm. The effect of temperature on the corrosion behavior in the absence and presence of 2.5 × 10−5 M of PCMB was studied (283–308 K). The associated activation energies (E a) and the thermodynamic parameters (ΔH*, ΔS*, K ads, ΔG°ads) for the adsorption process were determined. The ΔG°ads value is −36.55 kJ/mol, which indicated that the adsorption mechanism of PCMB on C-steel in 0.5 M H2SO4 solution was combined between physisorption and chemisorption processes.