Avaliação de inibidor anticorrosivo em meio contendo cloreto e CO2 para sistemas de aço carbono utilizados na indústria petroquímica: efeito da temperatura e da contaminação por O2

Abstract

Carbon steel is widely used in industrial production equipment, such as cooling tower systems, storage tanks, and transmission ducts. However, despite its excellent tensile and yield strengths, steel can exhibit low corrosion resistance depending of its alloying elements. To prevent deterioration, corrosion inhibitors are used to adsorb on the surface in a chemical, physical, or mixed manner, leading to the formation of an inhibitor film layer and reduction of the corrosion rate, making it an economical and useful option. This study investigated the influence of temperature and the presence of oxygen on the behavior of a tertiary amine-based inhibitor in low carbon steel. Potentiodynamic polarization and electrochemical impedance spectroscopy analyses were conducted at 25 ºC and 60 ºC in a saline solution of 3.5 % w/w NaCl saturated with CO2 and with the presence of oxygen (CO2 + 500 ppb O2), with different concentrations of the inhibitor. Surface characterization of this tertiary amine derivative was performed using Optical Microscopy. The results show that the adsorption of the inhibitor on the steel surface follows the Langmuir adsorption isotherm and that the mechanism involve both chemisorption and physisorption. The efficiency obtained from the inhibitor at a temperature of 25 ºC shows little discrepancy between environments with and without O2, reaching values around 90 %. With higher current densities and lower capacitive arcs, the results indicate that the highest efficiency of this inhibitor occurs at 60 ºC, achieving up to 95 % efficiency for a concentration of 25 ppm.