Pterocarpus santalinoides leaves extract as a sustainable and potent inhibitor for low carbon steel in a simulated pickling medium

The crude extract of Pterocarpus santalinoides leaves (PSLE) extracted using water, ethanol, and methanol as the extraction solvent has been studied as inhibitor for low carbon steel in 1 moL/dm³ HCl solution using electrochemical approaches at 25 °C and 60 °C. The results obtained reveal that, PSLE extract has the capacity to effectively suppress the dissolution of the studied substrate. The inhibition performance of PSLE is a function of concentration, temperature, and extraction solvent. Corrosion inhibition is in the order: ethanolic extract > methanolic extract > aqueous extract. With 0.7 g/L PSLE, inhibition efficiency of >90% has been obtained at 60 °C. Based on calculated values of adsorption parameters and UV–vis results, it is proposed that PSLE molecules chemically interacted with the substrate surface. PSLE extract suppressed both the rate of cathodic and anodic reactions according to the PDP results. However, aqueous PSLE extract inhibited anodic corrosion reactions predominantly while ethanolic and methanolic extracts mainly inhibited the cathodic corrosion reactions. Surface characterization studies via SEM, EDAX, and AFM provide experimental evidence to the claim of interaction and presence of PSLE molecules on the studied substrate surface.