Ricinus communis leaves extract as a green corrosion inhibitor for carbon steel in hydrochloric acid solution

Abstract

The eco-friendliness of Ricinus communis leaves extract as an inhibitor for carbon steel (CS) corrosion was evaluated using weight loss (WL) as a chemical technique, and some electrochemical methods like AC electrochemical impedance spectroscopy (EIS), Tafel polarization (PP), and electrochemical frequency modulation (EFM). The data acquired showed that the higher the dose of the extract, the higher the protection efficiency (% IE), which increases with increasing temperature from 80.5 at 25 °C to 91.4 % at 45 °C. Using adsorption isotherms, adsorption factors were determined. Activation parameters were calculated and discussed based on Arrhenius and transition state principles. The adsorption procedure of Ricinus communis leaves extract on CS surface was found to be spontaneous and follows Langmuir's isotherm. This extract is a mixed type according to polarization data. Based on EIS data, it was shown that the extract of Ricinus communis leaves decreased the capacitance double layer (Cdl) from 539 to 74 μF cm−2 while enhancing the charge transfer resistance (Rct) from 70 to 430.5 Ω cm2. Surface analysis was done using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) to measure the degree of surface roughness, film formation, and adsorbed groups on the CS surface. According to these tests, a layer of extract molecules forms on the CS surface.