Uso do extrato de Jucá (Caesalpinia ferrea) como inibidor verde de corrosão frente ao aço 1020 em meio ácido

Abstract

The AISI 1020 steel is one of the most used in industry for manufacturing of metal machines and equipment. However, this steel has low corrosion resistance in acid medium. Natural inhibitors do not emit toxic or harmful components to the environment, they are renewable, may have a lower cost, besides guaranteeing environmental sustainability and the use of natural residues. Studies reveal that the Juca (Caesalpinia ferrea) found in the Amazon has excellent antioxidant capacity. Juca extract in different concentrations (0.1 to 2.0 g.L-1) was used on the study of green corrosion inhibitor. Electrochemical analyzes were performed in an electrochemical cell composed of a working electrode of AISI 1020 steel. Measurements of Open Circuit Potential (OCP), Resistance to Linear Polarization (RLP) and Electrochemical Impedance Spectroscopy (EIS) were performed. Electrochemical methods have equivalent results for comparison purposes. Results confirm that the Juca extract acts as a mixed inhibitor of corrosion in AISI 1020 steels, where the inhibition efficiency was 94.8% in the concentration of 2.0 g.L-1. The adsorption was described and characterized by the Isotherm of Langmuir’s Adsorption and the value of ΔGoads, which revealed the occurrence of adsorption by physisorption. SEM and FEG-SEM indicated that the surface morphology of the substrate, in the presence of the Juca extract is composed of a compact, uniform and amorphous film, after the electrochemical tests. UV-Vis analyzes confirm the reduction of iron ions transfer to the solution as the inhibitor concentration is increased, proving the effectiveness of the inhibitor.