Polarization and impedance methods in corrosion inhibition study of carbon steel by amines in petroleum-water mixtures

Inhibition effects have been carried out on carbon steel in solutions containing different amines. These compounds were dissolved in some petroleum-water corrosive mixtures containing of acetic acid and NaCl. Corrosion inhibition afforded by ethylenediamine (EDA), hexylamine (HA). butylamine (BA), tert-butlamine (t-BA), propylamine (PA) and iso-propylamine (i-PA) has been studied by cyclic polarization (CP), electrochemical impedance spectroscopy (EIS) and optical micrography with a carbon steel rotating disk electrode at 25 degreesC. The best corrosion inhibition was obtained for the 4% of EDA, which is able to act as polarizing agent on the carbon steel surface. Thus, analysis of the change of inhibitor structure and its concentration in the Solution allowed us to find the optimum parameters for obtaining the best inhibition. The observed difference in behavior of the additives can be attributed to the differing of solubility in various solvents ratio and to the differing of strict hindrance of the compounds to metal surface. (C) 2002 Elsevier Science Ltd. All rights reserved.