Abstract: In oil and gas production environment, CO2, H2S and Acetic Acid (HAc) have become a main source that affect corrosion to the carbon steel and cause failures on the facilities. In order to minimize the failures, there must be a tool to predict those failures. This research proposed a prediction model incorporated with H2S and HAc in CO2 environments using a set of experiments. The experiments were conducted in the 3% NaCl solution saturated with 300 ppm of H2S in CO2 gas. LPR and EIS methodology were used to study corrosion mechanism and to calculate carbon steel corrosion rate. The results revealed that effects of H2S and HAc in CO2 environment have contributed in increasing corrosion rate. Those effects were caused by additional of cathodic activation reactions in the system as described by scan polarization. Analyzing through EIS showed that combined effect of CO2 and H2S promote to form film formation indicated by Warburg diffusion spectra. Although interaction of CO2 and H2S gas has a capability to produce film formation, the film can not inhibit corrosion reaction that may relate to the presence of HAc in the solution.