Characterization of corrosion scale formed on 3Cr steel in CO2-saturated formation water

The evolution of the corrosion scale formed on 3Cr steel was investigated by scanning electron microscopy (SEM) and X-Ray Diffraction (XRD). The inner layer was characterized by Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis differential scanning calorimetry (TG-DSC). The results show the inner layer is an amorphous-like structure containing some nano-quasicrystalline and nanocrystalline grains which is more uniform and less porous than the crystalline FeCO3 layer. At the 2nd stage, the transition of cathodic reactions was found, and the growth of the FeCO3 phase in the inner layer dramatically decreased the film porosity, resulting in the passivation. (C) 2016 Elsevier Ltd. All rights reserved.