Corrosion Characteristics of Gas–Liquid Two-Phase Flow in Horizontal Pipelines

In CO2 gas–liquid two-phase flow environments, corrosion behavior within low-pressure gathering pipelines is complex and severe. Conventional corrosion monitoring techniques struggle to accurately capture its dynamic and nonuniform characteristics due to low spatial resolution and response lag. This paper develops a ring array electrical resistance probe corrosion monitoring system capable of synchronous multipoint circumferential monitoring along pipelines to investigate the corrosion behavior of 20# carbon steel at different locations under four CO2 partial pressures (20–150 kPa) and three flow patterns (stratified flow, wave flow, and slug flow). Research findings indicate that flow pattern is a key factor governing corrosion rates. Under slug flow conditions at a partial pressure of 150 kPa, the initial corrosion rate reached 2.0 mm/year, approximately 1.7 times that observed under wave flow conditions and five times that under stratified flow conditions. The corrosion rate increased with rising CO2 partial pressure. More pronounced differences were observed at the gas–liquid interface and within the liquid phase compared to the gas phase. Under wave flow conditions, raising the CO2 partial pressure from 20 to 150 kPa increased the corrosion rate at the gas–liquid interface by approximately 80%, whereas the gas phase showed only a 15% increase. This study quantitatively elucidates the coupled effects of flow pattern, CO2 partial pressure, and phase distribution on corrosion behavior, providing direct evidence for real-time corrosion risk assessment and protection of low-pressure gathering pipelines in CCUS/EOR systems.