Corrosion inhibition of low-carbon steel in hydrochloric acid environment using a Schiff base derived from pyrrole: gravimetric and computational studies

• A. Alamiery, E. Mahmoudi and T. Allami

Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment, University Kebangsaan Malaysia (UKM), P.O. Box: 43000, Bangi, Selangor, Malaysia

Abstract: Corrosion inhibitors are used to decrease the corrosion process of metals in acid and/or basic solutions. Corrosion inhibitors are organic molecules containing polar sites such as phosphorous, sulfur, oxygen, and/or nitrogen atoms in addition to heterocyclic and aromatic rings and conjugated p-systems. A new Schiff base derivative from pyrrole, namely N´-(1-phenylethylidene)-4-(1H-pyrrol-1-yl)benzohydrazide (N–PB), was synthesized from acetophenone and 4-(1H-pyrrol-1-yl)benzohydrazide. The chemical structure of the newly synthesized inhibitor molecule was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopical techniques in addition to CHN (carbon, hydrogen, and nitrogen) micro-elemental analysis. It was studied as a low-carbon steel corrosion inhibitor in 1 M hydrochloric acid solution by the weight loss and scanning electron microscopy (SEM) methods. The inhibition efficiency of the synthesized inhibitor (N–PB) reached a maximum of 94.5% at 500 ppm concentration. The presence of N–PB inhibitor decreases the corrosion rate (C_R) due to the formation of a protective adsorption layer on the surface of low-carbon steel. The adsorption of N–PB molecules obeys the Langmuir adsorption isotherm model. The density functional theory (DFT) evaluated parameters such as HOMO (highest occupied molecular orbital), LUMO (lowest occupied molecular orbital) and the energy gap (ΔE=E_HOMO–E_LUMO) (indicate the excellency of the corrosion inhibitor. The gravimetrical, SEM, and theoretical findings are in harmony.

Keywords: phenylethylidene, corrosion inhibitor, DFT, LUMO, Langmuir, low carbon steel

Int. J. Corros. Scale Inhib., 2021, 10, no. 2, 749-765 PDF (755 K)
doi: 10.17675/2305-6894-2021-10-2-17

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