Among the various corrosion processes in steels, it is well recognized that the presence of carbon dioxide and water can promote CO2 corrosion. This type of corrosion is most commonly found in pipelines and wells of the oil and gas industry. The intensity and occurrence of this type of corrosion are dependent on factors such as solution pH, temperature, and pressure. Therefore, the probability of forming an oxide layer (FeCO3), which can be either protective or not is dependent on its conditions formation. This dissertation aimed to evaluate the thermodynamics involved in the precipitation of FeCO3 layer, by varying the time and temperature and verifying the influence on the ionic strength and Fe2 plus and CO32 minus concentration. The species (H plus, OH minus, HCO3 minus, CO32 minus, and CO2(aq)) chemical concentration were calculated from mass and ionic equilibrium balance of the CO2 dissociation in ionic aqueous solutions. In corrosion tests, steels were immersed in a solution of 3 per cent NaCl for periods of 7, 15, 21 and 30 days and temperatures of 25 Celsius degrees, 50 Celsius degrees and 75 Celsius degrees in an atmosphere of CO2 and N2 75 bar. The FeCO3 layer formed on the surface of steel can reduce the corrosion rate by hindering the diffusion of the species involved. Thus, surface and cross section morphologies of FeCO3 layers formed were characterized by scanning electron microscopy (SEM), and the techniques of X-ray fluorescence energy dispersive (EDS) and spectroscopy. X-ray photoelectron (XPS) were used to study the chemical composition and configuration of the layer. The result of this characterization showed the formation of FeCO3 for temperatures studied. However, in terms of morphology at 50 Celsius degrees the layers showed the greatest thickness and at 75 Celsius degrees were smallest corrosion rates.