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

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.

本研究采用电化学阻抗谱（EIS）、极化曲线、扫描振动电极技术（SVET）及重量损失法，探究了从蓖麻（Ricinus communis）中获取的蓖麻树皮粉末对0.5 mol·L⁻¹盐酸酸性介质中AISI 1020碳素钢的缓蚀效果。研究采用傅里叶变换红外光谱（FTIR）与扫描电子显微镜（SEM）作为表征手段。电化学阻抗谱与重量法结果显示，缓蚀效率随缓蚀剂浓度升高而提升，最高可达83%。极化曲线测试表明，蓖麻树皮粉末属于混合型缓蚀剂。其组分在金属表面的吸附行为遵循朗缪尔吸附等温式。傅里叶变换红外光谱分析证实，粉末中存在碳、氮、氧杂原子，这些杂原子主要结合于与蓖麻油酸类羧酸相关的官能团中，该类官能团或为粉末缓蚀性能的来源。扫描电子显微镜分析显示，当电解液中添加该缓蚀剂时，碳钢的腐蚀过程受到抑制，这一结论得到了扫描振动电极技术测试结果的验证。综上，实验结果表明，蓖麻树皮粉末具备作为酸性介质中碳素钢缓蚀剂的应用潜力。