Experimental and theoretical studies of aminothiophene derivatives inhibitors on carbon steel corrosion in perchloric acid medium

Abstract

The effect of two aminothiophene derivatives, namely (2-amino-4-phenylthiophene-3-carbonitrile) APTC and (2-amino-4-p-tolylthiophene-3-carbonitrile) ATTC, as carbon steel corrosion inhibitors in a perchloric acid medium was investigated. The study was performed by weight loss method, quantum chemical calculations (DFT) and Scanning electron microscope (SEM). The impact of the two aminothiophene derivatives as inhibitors was positively correlated with concentration, temperature, and exposure time. The value of the active energy of the inhibition corrosion reaction of carbon steel is greater than that obtained for the blank solution. All experimental data were consistent with the Langmuir adsorption isotherm, and the value and sign of the adsorption free energy obtained indicated that the inhibitor molecules were spontaneously adsorbed on the carbon surface by a mixed adsorption mechanism. The SEM surface analysis showed the formation of a protective organic film on the steel surface. The DFT supported the experimental results and showed that the inhibition effect is structure-dependent.