The nature of corrosion scales formed on super 13Cr stainless steel surface after exposure in formate completion fluid in the presence of various aggressive substances was investigated by a combination of surface characterization techniques such as SEM/EDS, XRD, Raman, etc. The results indicated that the corrosion products mainly comprised Fe3O4 for super 13Cr exposed to KCOOH at 180°C under N2 environments. However, the addition of CO2 progressively increased the general corrosion rate, suggesting that the calculated high corrosion rates were attributed to the presence of CO2 in the system tested. The formation of FeCr2O4 and Cr(OH)3 were detected in the inner corrosion product layers and the precipitation of blade-shaped iron carbonate (FeCO3) was detected in the outer layer on the super 13Cr stainless steel surface. The results suggested that the outer corrosion product layer showed less corrosion protectiveness compared to the formation of nano-polycrystalline FeCr2O4 and Cr(OH)3 inner layers, based on its less compact and observed gaps between crystals from the SEM images. The presence of Sulfur on the metallic surfaces in both N2 and CO2 environments caused the increase in material degradation.

Subject
X-ray diffraction, Steel surfaces, Materials, Corrosion rate, Formates, Corrosion detection, Corrosion products, Corrosion scales, Anodic reactions, Fluids, Scale formation, Immersion, Stainless steel
Keywords:
Potassium formate, super 13Cr stainless steel, high temperature, CO2, sulfide
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2021
Association for Materials Protection and Performance (AMPP)
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