Water-wetting is a crucial issue in CO2 corrosion of multi-phase flow pipelines made from mild steel. This study demonstrates the use of a novel benchtop apparatus, a horizontal rotating cylinder, for study of the effect of water wetting on COa corrosion of mild steel in two-phase flow. The setup is similar to a standard rotating cylinder except for its horizontal orientation and the presence of two phases - typically water and oil. The apparatus has been tested by using mass transfer measurements and CO2 corrosion measurements in single-phase water flow. CO2 corrosion measurements were subsequently performed using a water/hexane mixture with water cuts varying between 5 and 50%. While the metal surface was primarily hydrophilic under stagnant conditions a variety of dynamic water wetting situations was encountered as the water cut and fluid velocity were altered. Threshold velocities were identified at various water cuts when the surface became oil-wet and corrosion stopped.