The integrity of CO₂ transport infrastructure is a critical component of the carbon capture and storage (CCS) value chain. Appropriate material selection is essential to ensure safe containment of captured CO₂, particularly as large-scale CCS deployment is required to achieve meaningful progress toward net-zero targets. However, pre-treatment of CO₂ to meet stringent specifications remains both technically challenging and economically costly. The presence of moisture and other impurities can significantly exacerbate corrosion of metallic components, especially carbon steel, through the formation of carbonic acid and stronger acids such as sulfuric and nitric acids. Dense-phase CO₂ also affects the performance of non-metallic materials, including elastomers and polymers, through mechanisms distinct from metallic corrosion, such as plasticisation and rapid gas decompression.

In this study, semi-crystalline polymers were investigated following exposure to supercritical CO₂. Tensile testing and dynamic mechanical analysis (DMA) were used to evaluate changes in mechanical and thermal properties relative to pristine samples. Post-exposure the samples exhibited an increase in elongation at break of more than 67%, accompanied by a reduction in glass transition temperature from 53.3 °C to 19.7 °C, indicating significant plasticisation. Scanning electron microscopy revealed morphological damage in the polymer after exposure to supercritical CO₂. In parallel, carbon steel X56, commonly used as a pipeline material, was exposed to supercritical CO₂ under varying moisture contents to assess the severity of corrosion.

The findings highlight critical gaps in understanding the long-term performance of both metallic and non-metallic materials in CCS applications, particularly with respect to the role of CO₂ impurities. These insights are also directly relevant to the assessment and qualification of existing infrastructure for repurposing in CO₂ service, where legacy materials may exhibit behaviour distinct from that of pristine materials.