The presence of carbon dioxide (CO2) and water in the fluid can cause severe internal corrosion in the pipelines. This study aims to observe corrosion behavior during the changes in flow rate and acidity conditions in order to obtain the relationship between the parameters by the measured corrosion rate. Corrosion rate measurements were performed for API 5L X52 steel material by using polarization method in 3.5% NaCl solution with saturated CO2 injection. Solution with different acidity were applied which has pH 4, 5, and 6 respectively. To simulate the flow rate, a Rotating Cylinder Electrode RCE was used at various rotation rates 0, 375, 750, 1500, and 3000 rpm, at room temperature (25 °C) and atmospheric pressure. Based on testing results, the changes in rotation converted to flow rate showed that the corrosion mechanism of API 5L X52 steel in NaCl solution with saturated CO2 content was mainly controlled by mass transport at pH=4 whereas chemically controlled involved both at pH=5 and pH=6 conditions.