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.
Highlights
Metals and alloys are widely used in industrial applications such as automobiles, petroleum refining, architecture and others
One of the by-products generated during castor oil production is the bark, and the aim of the present work is to investigate the potentiality of castor bark (Ricinnus communis) powder as corrosion inhibitor for AISI 1020 carbon steel in acidic media (HCl 0.5 mol.L-1) using electrochemical techniques and weight loss measurements
Absorption peak at 2923 cm-1 can be assigned to C-H and its low intensity indicates that only short chain compounds are detected[27,28]
Summary
Metals and alloys are widely used in industrial applications such as automobiles, petroleum refining, architecture and others. Carbon steel has an important place due to its low cost, good mechanical properties and workability, thermal conductivity, etc. This material has low corrosion resistance in acidic media, which can lead to economic losses. One of the proposed inhibitory mechanisms consists in the adsorption of the molecules to the metal surface, creating a barrier between the metal and the electrolyte, blocking active sites and reducing the metal dissolution and/or reduction reactions[3] Many of these inhibitors are organic molecules containing nitrogen, oxygen, sulphur, and phosphorous heteroatoms in their structures, which can adsorb into active sites of the metal surface through conjugated bonds[4]
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