Eliane D’Elia

Synthesis of Thiourea Derivatives and its Evaluation as Corrosion Inhibitor For Carbon Steel

GRAPHICAL ABSTRACT Abstract The inhibitory effect of thiourea-based compounds was evaluated using carbon steel body specimens in hydrochloric acid media. Thiourea derivatives, N-(pyrimidin-2-ylcarbamothioyl)benzamide and N-(6-methylpyridin-2-ylcarbamothioyl)benzamide, were synthesized using a simple route with good yields of approximately 70%. The inhibitory efficiencies were obtained by means of weight-loss experiments and electrochemical techniques (e.g., polarization curves and electrochemical impedance spectroscopy). The presence of a methyl functional group showed a better inhibitory efficiency compared with the derivate inhibitor without such modification. Analyzing Langmuir isotherms, ΔG0ads values indicate the chemical adsorption of thiourea-based compounds. The ECorr values obtained for the thiourea derivative with the methyl functionality was cathodically shifted by approximately −0.08 V, with an inhibition efficiency of 81%.

Electrochemical behavior of the cistein and diphosfonate for stainless steel in media of HCl 1 mol L-1

Amino acids and self assembled monolayers (SAMs) have been studied as to their inhibiting action on the corrosion of metallic materials. The objective of this work is to study the electrochemical behavior of the cisteincisteine, the diphosfonate and the mixture of both in inhibiting the action of corrosion on stainless steel 304 in HCl 1 molL-1. As the following techniques were used: open circuit potential (OCP), potenciostatic anodic polarization (AP), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) and optical microscopy (OM). The results of CA showed that cisteine has a double effect, catalytic and inhibiting, in function of the immersion time of the metallic part in the electrolytic solution. AP curves have shown lesser current density for the system containing cisteine + diphosfonate, suggesting an inhibiting synergic action. These results have been confirmed by EIS and OM.