Pomelo leaves extract as a green corrosion inhibitor for carbon steel in 0.5 M HCl

Abstract

The current work presents a simple, low-cost, and eco-friendly method for carbon steel corrosion retardation in 0.5 M HCl in a temperature range of 293–313 K. The pomelo plant, which is widespread all over the world, is regarded as a rich source of phytochemical compounds. The maceration method was adopted for pomelo leaf extraction (PLE) and n-hexane was used as a solvent (HPLE). The extract components were identified using Gas Chromatography–Mass Spectroscopy (GC-MS) and Fourier transform infrared spectroscopy (FTIR). These characterization methods confirm that HPLE is a rich source of phytochemicals such as alcohols, esters, ethers, alkenes, and ketones. The corrosion investigation was accomplished by electrochemical measurements and scanning electron microscopy (SEM). Potentiodynamic polarization curves for different inhibitor concentrations (0, 25, 50, 75, and 100 ppm) showed that HPLE behaves as a mixed type inhibitor with a maximal inhibition efficiency of about 82% at 100 ppm. The metal surface study was carried out by scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). The data obtained from SEM and EDX data are compatible with those obtained from the electrochemical experiments. Metal surface studies proved the presence of a protective film that is constructed by adsorption of inhibitor molecules on the metal surface. Thermodynamic adsorption isotherm calculations show that the adsorption of HPLE on the mild steel surface obeys the Langmuir adsorption isotherm.