Estudo da suscetibilidade à corrosão de aços carbono em meio de NaCl 3,5% utilizados como armaduras de tração em risers

Abstract

This study aimed to evaluate the corrosion susceptibility of carbon steels used as tensile reinforcements in flexible risers, which are critical structures in offshore operations within the oil and gas industry. The research focused on two types of carbon steel, with carbon contents of 0.27% and 0.80%, under simulated exposure conditions to corrosive environments using sodium chloride (NaCl) solution with and without carbon dioxide (CO₂), and subjecting the samples to temperatures of 25 C and 40 C. To this end, electrochemical tests were conducted, including Open Circuit Potential (OCP), Electrochemical Imp edance Spectroscopy (EIS), Potentiodynamic Polarization (PP), and Electrochemical Frequency Modulation (EFM), along with microstructural analysis before and after testing. The results showed that the steel with higher carbon content (0.80%C) exhibited greater susceptibility to corrosion, especially in the presence of CO₂, due to the formation of unstable corrosion products and lower resistance to current flow. In contrast, t he 0.27%C steel demonstrated superior performance, as evidenced by larger semici rcles in Nyquist plots and lower corrosion current density. Microstructural analysis supported the electrochemical data, revealing greater degradation on the surfaces of the higher carbon specimens. These findings underscore the importance of selecting app ropriate carbon content in steels used in aggressive environments, contributing to corrosion mitigation strategies and enhancing the durability of structural components.