• carbon steel;
  • corrosion inhibitor;
  • Croton cajucara Benth;
  • microemulsion system;
  • saline corrosion


Application of corrosion inhibitors is one of the most common practices for the protection of steel structures and their alloys in industry. Since metallic corrosion is a major cause of economic losses in the oil industry, the use of natural inhibitors is an alternative for sustainable technological development. In the present study the effectiveness of the hydroalcoholic extract of the plant species Croton cajucara Benth (CC) dissolved in a microemulsion system (MES-CC) as well as in dimethyl sulfoxide (DMSO-CC) was evaluated as corrosion inhibitor on carbon steel AISI 1020 in saline medium. Surface tension measurements of the MES-CC confirmed micelle formation, and rheological data showed that viscosity varies with temperature. According to potentiodynamic technique and Tafel extrapolation, maximum inhibition efficiencies were effective (93.84% for MES-CC and 64.73% for DMSO-CC) with predominant control of cathodic reaction. The adsorption of MES-CC on carbon steel surface obeys Langmuir adsorption isotherm, while DMSO-CC was found to follow the Frumkin isotherm.