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, G 0 ads values indicate the chemical Downloaded by [University of Sherbrooke] at 15:32 12 April 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 adsorption of thiourea-based compounds. The E Corr values obtained for the thiourea derivative with the methyl functionality was cathodically shifted by approximately −0.08 V, with an inhibition efficiency of 81%.

Corrosion inhibitors have been used to preserve the integrity of metal components of plant facilities under severe corrosive conditions that would lead to failure or reduction of the operating cycle of essential units. These include risers, columns, wells, pipelines, pressure vessels and distillation towers structures. Several compound classes have been studied as corrosion inhibitors for metallic materials. In special, organic compounds have been tested and applied industrially as corrosion inhibitors due to their low toxicity. Taking into account recent recommendations for eliminating the use of toxic inorganic inhibitors there was a significant increase in studies on the use of natural products as corrosion inhibitors. Natural products are considered environmentally suitable corrosion inhibitors for use on a large scale. Recent studies have shown that black pepper extract is rich in a mixture of alkaloids substances that have excellent anti-corrosion properties in acid conditions. The aim of this study was to investigate the carbon steel corrosion inhibition efficiency of black pepper crude extract and purified piperine (major alkaloid present in the extract) in highly corrosive environment by weight loss measurements. For this reason, weight loss tests were carried out to study the inhibition efficiency. The inhibition efficiencies of different concentrations of the black pepper crude extract was higher than the efficiencies of the same concentrations of pure piperine. The efficiencies were about 97 % for the crude extract and 70 % for the pure piperine.

No abstract

No abstract

No abstract