Evaluation of Castor Bark Powder as a Corrosion Inhibitor for Carbon Steel in Acidic Media

Abstract

The inhibition effect of castor bark powder obtained from Ricinus communis on AISI 1020 carbon steel in acidic media (HCl 0.5 mol.L -1 ) has been studied by electrochemical impedance spectroscopy (EIS), polarization curves, scanning vibrating electrode technique (SVET) and weight loss measurements. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed as characterization techniques. The EIS and gravimetric results showed that the inhibitory efficiency increases with inhibitor concentration achieving 83%. Polarization curves indicated that the castor bark powder acts as mixed inhibitor. The adsorption of the powder components on the metal surface follows the Langmuir isotherm. The FTIR analyses indicate the presence of C, N and O heteroatoms, incorporated in functional groups mainly related to the presence of carboxylic acids as ricinoleic acid, which could be responsible for the inhibitory properties of the powder. SEM analyses showed that the corrosion process was retarded in the presence of inhibitor in the electrolyte, which was confirmed by SVET measurements. Therefore, the results indicate that castor bark powder has potential to be a corrosion inhibitor for carbon steel in acidic media.

Aqueous Extracts of the Castor Beans as a Corrosion Inhibitor of Mild Steel in HCl Media

“…This phenomenon could be attributed to the chemisorption involving the charge transfer from the aqueous castor beans extract molecules to the mild steel surface. This behavior is different from the one presented by Santos et al, 14 where they concluded that the interaction between the molecules of the castor bark powder and the metal surface was physical due the ΔG°a ds calculation, which is in our point of view inappropriate.…”

“…About the ΔG°a ds calculation performed by Santos et al, 14 in our previous works, 1,2,[10][11][12] we have shown that the determination of thermodynamic parameters such as ΔG°a ds was not possible, even when placing the water concentration in mg L −1 , due the unknown chemical nature of the adsorbed molecules.…”

“…Good inhibition efficiencies can be achieved, reaching 98% for corrosion of carbon steel in HCl solution using the garlic peel and sunflower bean hull extract. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] About the garlic peel extract, the authors 22 suggested based on headspace solid-phase microextraction-gas chromatography (HS-SPME-GC) analysis of the extract that sulfur compounds may play an important role in the inhibition process. In the sunflower bean hull study, 5 the authors suggest a complex between the functional groups present in the extract molecules (fatty acid, phenolic acid, amino acid, furfural, xylose and anthocyanin) and Fe 2+ ions as the adsorbed species responsible for the inhibitory action.…”

“…Santos et al 14 examined the effect of castor bark powder on the corrosion of 1020 carbon steel in 0.5 M HCl. Inhibition efficiency varied from 65 to 83%, and it was determined by gravimetric and electrochemical tests.…”

Uso de extratos naturais como inibidores de corrosão para o aço AISI 304

“…A erva mate (I. paraguariensis) é uma espécie vegetal nativa das regiões subtropicais e temperadas da América do Sul, o extrato desta erva e de outras folhas pode ser utilizado como inibidor de corrosão para aço inoxidável em soluções ácidas (Santos et al, 2017).…”