Corrosion Inhibition Performance of Biomolecules Isolated from Salsola imbricata for N80 Steel in 15% HCl Acidizing Environment

This study investigated the efficacy of two fatty fractions (referred to as HF2 and HF5) obtained through chromatographic analysis of the n-hexane extract of the Saudi-origin plant Salsola imbricata in inhibiting corrosion of N80 steel in a 15% HCl solution, under both static and hydrodynamic conditions. The full identification of the phytochemical components in the two fractions was accomplished through gas chromatography–mass spectrometry (GC–MS) analyses. The influence of inhibitor concentration and the temperature of the acid medium was taken into account, and the outcomes were assessed through weight loss, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP). The results demonstrated that the efficacy of the purified fatty mixtures increased as the concentrations increased, reaching its maximum potency of 76.69 and 91.46% for HF2 and HF5, respectively, at a temperature of 40 °C. Fraction HF5 exhibited exceptional performance, achieving maximum efficiency at 500 ppm at 40 °C. It exhibited superior performance compared to HF2 in all tested conditions. Remarkably, the efficiencies of both fatty mixtures exhibited an upward trend with temperature reaching 40 °C and subsequently declined as the temperature continued to rise up to 90 °C. The main process of corrosion inhibition was determined to be the adsorption of isolated molecules in the two fractions onto the steel surface which was confirmed by surface assessment utilizing scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), atomic force microscopy (AFM), and optical profilometry (OP).