Water wetting is a crucial issue in carbon dioxide (CO_2) corrosion of multiphase flow pipelines made from mild steel. This study demonstrates the use of a novel benchtop apparatus, a horizontal rotating cylinder, to study the effect of water wetting on CO_2 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 CO_2 corrosion measurements in single-phase water flow. CO_2 corrosion measurements were subsequently performed using a water/hexane mixture with water cuts varying between 5 percent and 50 percent. 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.
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