The performance of SAE 1010, API K55 and API N80 steels were evaluated in terms of resistance to corrosion with the use of two CO2-saturated saline solutions (NaCl and CaCl2, both at the concentration of 0.5 M) and wet supercritical CO2 at a temperature of 90°C under 15 MPa for 07 days. Mass loss tests were performed to determine corrosion rates and the films of corrosion product evaluated by scanning electron microscopy and potentiodynamic polarization technique. Lower corrosion rates were obtained in a wet supercritical CO2 medium. The degree of protection offered by corrosion products films depended not only on the steel but also on the corrosive medium and kind of salt present.

Two types of polymeric coating were applied on an AISI 1020 steel, where one of them was reinforced by carbon nanotubes, with the objective of protection against corrosion in a medium containing saline solution, NaCl 3% wt satured with CO2, at 75 bar and tested at 50oC and 75oC for 360 hours. Electrochemical techniques, such as Linear Polarization Resistance, (LPR), Electrochemical Impedance Spectroscopy (EIS), Tafel curves and weight loss method, were used for coating evaluation performance. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were used to determine both the morphology and chemical composition of the layer formed on the analyzed surfaces. The coating adhesion to metallic surface was evaluated using pull-off test according to ASTM D4541-09. For the studied conditions, the results obtained showed that there was no adequate coating protection, occurring failures and indicating that both coatings may not be used in the tested conditions.