Avaliação da eficiência de inibição de líquidos iônicos próticos como inibidores de corrosão para o aço A36 em ambientes com variação de temperatura e saturado em CO2

Abstract

ASTM A36 steel is a widely used low-carbon steel, with one of its most common applications being in oil and gas pipelines due to its good mechanical properties and availability. However, the presence of corrosive agents like CO2 and NaCl can significantly accelerate its degradation. To mitigate this process, a primary strategy employed is the use of corrosion inhibitors that are nontoxic, low-cost, and environmentally friendly. In this context, protic ionic liquids have emerged as potential inhibitors due to their versatility and ease of chemical synthesis. In this study, two protic ionic liquids were evaluated for their inhibitory efficiency: ethanolamine with carboxylic acid and diethanolamine with carboxylic acid. Tests were conducted in a simulated corrosive medium consisting of a 3.5% NaCl solution saturated with CO2 gas. Inhibitor concentrations (250, 500, and 1000 ppm) and temperature (25, 40, and 60 °C) were varied. Weight loss tests, Open Circuit Potential, and Electrochemical Impedance Spectroscopy were used to assess corrosion inhibition efficiency. Additionally, Optical Microscopy and Atomic Force Microscopy analyses were performed for surface characterization. The results from weight loss and electrochemical tests demonstrated that the protic ionic liquids used were effective in reducing the corrosive process, achieving efficiencies greater than 80% under the best conditions evaluated. Surface characterization also showed the effectiveness of the inhibitors compared to the sample without inhibitor.