DEVELOPMENT OF SAGA (ABRUS PRECATORIUS) SEED EXTRACT AS A GREEN CORROSION INHIBITOR IN API 5L GRADE B UNDER 1M HCL SOLUTIONS

The critical role of newly green corrosion inhibitors shows the disruption of cathodic and anodic reactions at the metals and solution interface. The object of this study is the development of Saga as a corrosion inhibitor to mitigate the effect of corrosive HCl 1M оn mild steel. The inhibitor was extracted using methanol to prepare various concentrations. Fourier transform infrared (FTIR) spectroscopy was used to determine the functional group of the inhibitor. The electrochemical impedance spectroscopy aided by the potentiodynamic polarization was utilized to evaluate the inhibitor’s effectiveness. Optical emission spectroscopy (OES) was implemented to determine the percentage of elements in mild steel. Based on the FTIR results, C=O, -OH, C=C, benzene, and C-O are accountable for the inhibitor to donate its lone pair of an electron to the 3-d orbital of iron metal. Increasing the inhibitor concentration decreases the capacitive double layer to elevate the inhibitor resistance. The higher inhibitor resistance of 29.33 Ω cm^-1 increases as the concentration increases due to the depression of Cdl 420.16 μF cm² at 10 ml inhibitor solution. Parallelly, it increases the inhibition efficiency at 65.58 %, slightly lower than the PP measurement of nearly 88 %. The higher value of adsorption/desorption constant, Kads, at 2.9 L mol^-1 shows the strength of the inhibitor, which lowers the value of Gibbs free energy (ΔGads). The Saga inhibitor is considered a chemisorption inhibitor ΔGads –36.87 kJ/mol. The value demonstrates the formation of dative covalent bonding, which promotes the transferred electron from the inhibitor to the substrate. On the other hand, the Saga inhibitor abides by the Langmuir adsorption isotherm as the R² value is 0.99