Abstract The results of flow loop corrosion experiments carried out with 5 bar CO2, 0.5 bar H2S, 50% MEG and 60°C are presented and discussed in detail, with focus on development of localized corrosion attacks and the composition and morphology of corrosion product layers. The salinity and pH were adjusted to simulate either a pH-stabilized monoethylene glycol (MEG)/water phase or a non-treated MEG/water phase (baseline) containing some formation water. It was found that alkaline chemical treatment for corrosion control (pH stabilization) was inefficient against localized sour corrosion under these condition, and in some cases triggered development of large wide localized attacks. The findings are discussed based on recent knowledge on iron sulphide growth and breakdown mechanisms, and flow effects.