Volume 56

Study on corrosion behavior of X65 steel in supercritical CO2 based on in-situ EN measurement Liu Guangyu, Li Yuxing

Abstract

In the context of dual carbon goals, the transport of supercritical CO2 is a crucial component of Carbon Capture, Utilization, and Storage (CCUS) technology. However, the internal corrosion mechanisms and processes of these pipelines are complex. Due to the unique corrosion environment within supercritical CO2 pipelines, traditional electrochemical testing and in-situ electrochemical detection are challenging. Therefore, this study used in-situ electrochemical noise monitoring to investigate the corrosion behavior of X65 steel under various conditions of supercritical CO2. Corrosion rates were measured using the weight loss method, and microstructural characterization was performed. The results indicated that in the supercritical CO2 corrosion environment, electrochemical current noise (ECN) exhibited distinct pitting characteristics, suggesting that the corrosion behavior of X65 steel was primarily pitting corrosion. As the water content increased, the amplitude of ECN fluctuations also increased, indicating that the susceptibility to pitting corrosion in X65 steel increased with higher water content, making pitting initiation more likely. The high-frequency linear region slopes of the power spectral density (PSD) of the current noise were much less than -20 dB/dec, further confirming the pitting corrosion type. Corrosion rate calculations showed that the corrosion rate increased with higher water content. Microstructural characterization of the corrosion product films revealed that with increased water content, there was some delamination of the films and noticeable pitting, indicating that the primary corrosion behavior was localized corrosion. This study provides technical support for in-situ electrochemical detection in high-pressure thin liquid film environments within supercritical CO2.

Keywords CCUS; CO2 corrosion; EN