The effect of the surface roughness is believed to contribute on corrosion rate and on corrosive wear in CO2 gas system. Surface roughness affects the hydrodynamic and mass-transfer boundary layer which can influence electrochemical and mechanic-chemical behavior of a surface. Study effects of surface finish is important to predict corrosion rate that happen in the as-delivered internal pipe surface condition. In this research, the influence of surface morphology, represented by roughness, was used to study effect of surface roughness on corrosion rate in CO2 gas condition. The experiments used the specimens which were abraded using SiC abrasive paper of 60, 240, 400, 600, 800 and 1200 grit on the surface. The specimen used was carbon steel BS 970 (070M20). The specimen was tested at pH 5.5, 3 wt. NaCl, in static and turbulent flow solution saturated with CO2 gas condition. The corrosion rate was measured by the three corrosion measurements methods: Linear Polarization Resistance (LPR), weight loss and Electrochemical Impedance Spectroscopy (EIS). Experimental results showed that the corrosion rate increased with increasing surface roughness either in static or in turbulent flow condition. The corrosion rate in the turbulent flow was higher than in static condition for all surface finish.