Experimental and Quantum Chemical Studies on Corrosion Inhibition Effect of Synthesized Organic Compounds on N80 Steel in Hydrochloric Acid

The inhibition effect of synthesized 2,4-bis­(phenyl)-1H-benzodiazepine (BPBD) and 2,4-bis­(methoxyphenyl)-1H-benzodiazepine (BMBD) on corrosion of N80 steel in 15% HCl solution was investigated using weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques. The experimental results show that the inhibition efficiency of studied inhibitors increased with an increase in inhibitors concentration but decreased with an increase in temperature. Corrosion inhibition efficiency of 95.6 and 93.4% were obtained with 200 ppm of BMBD and BPBD, respectively at 303 K. The potentiodynamic polarization measurements indicated that both of the inhibitors are of mixed type. The adsorption of these inhibitors was found to obey Langmuir adsorption isotherm. The mechanism of the inhibition process was discussed in the light of the chemical structure and quantum chemical calculations of the investigated inhibitors. Scanning electron microscopy was used to characterize the surface morphology of the N80 steel specimens in the presence and absence of inhibitors.