Influence of flow on corrosion mechanisms of API 5L X65 carbon steel in CO2 environments (RIP2026-00096)

Carlos Vieira Masalla, RHUAN SOUZA, Luan Carrera Santos, Mário Luis Ferreira da Silva, Guillermo Vilalta-Alonso, Jose Antonio Da Cunha Ponciano Gomes , Alysson Helton Santos Bueno

Universidade Federal de Sao Joao del-Rei, Universidade Federal de São João del-Rei, Universidade Federal de Sao Joao del-Rei, Universidade Federal de São João del-Rei, Labcorr – Universidade Federal do Rio de Janeiro, Universidade Federal de São João del-Rei

Internal corrosion in pipelines is influenced by various physicochemical and hydrodynamic factors that act simultaneously on the steel surface. Variations in flow, temperature, CO₂ pressure, and the presence of contaminants such as salts and organic acids can affect the formation, stability, and adhesion of FeCO₃ films, impacting both uniform and localized corrosion. In this work, the corrosion behavior of API 5L X65 carbon steel was evaluated under static and dynamic autoclave conditions in order to assess the influence of flow on corrosion mechanisms in CO₂-containing environments.
For the static conditions, immersion tests were performed in an autoclave by varying temperature, CO₂ pressure, and acetic acid concentration, allowing comparison of different conditions of corrosion product formation and film adherence. The results indicated that increasing temperature and CO₂ pressure led to higher corrosion rates, even in the presence of FeCO₃ films. The addition of acetic acid further increased the corrosion rate due to medium acidification and the impairment of the formation of a protective film.
To simulate flow conditions, an autoclave system equipped with a rotating cage was employed, in which samples containing artificial defects of different diameters were tested to investigate the propagation of localized corrosion. Through this methodology, it was observed that introducing flow resulted in elevated corrosion rates, partial detachment of FeCO₃ films at specific surface regions, enlargement of the artificial defects, and the formation of natural pits.
In addition, Computational Fluid Dynamics (CFD) analyses were carried out to determine the distribution of wall shear stress on the specimen surface, enabling correlation between flow effects, corrosion product film behavior, and the intensification of metal dissolution.
Therefore, it is verified that the interaction between physicochemical parameters and hydrodynamic effects plays a critical role in increasing corrosion rates and influencing the stability of FeCO₃ films, directly affecting the aggressiveness of both uniform and localized corrosion in CO₂-rich environments.