The corrosion behavior of 13Cr-martensitic stainless steel was investigated in CO2-H2S-Cl− environments typical of oil and gas wells under different CO2 and H2S partial pressures, with an NaCl content of 50 g/L, pH = 2.7 and 4.8, T = 80°C.

The 13Cr was highly corrosion resistant to CO2-induced phenomena (general corrosion and carbonate stress corrosion cracking [SCC]), while the presence of H2S resulted in high sulfide stress corrosion cracking (SSCC) susceptibility and high corrosion rates. Moreover, the CO2 in CO2-H2S-Cl− systems inhibited general corrosion and SSCC phenomena by favoring the formation of a protective film. X-ray photoelectron spectroscopy (XPS) analysis of the films grown in different environmental conditions revealed:

  • CO2 favors the growth of a Cr oxide-rich protective film with a low Fe oxide-sulfide content;

  • the presence of H2S favors the formation of less protective Fe sulfide- and Fe oxide-rich layers.

An index of protectiveness Ip = Cr3+/(Cr3+ + Feox) was defined and related to the environmental parameter EH2S,CO2=pCO2/pH2S+pCO2 and to the actual corrosion rates.

Subject
Scanning electron microscopy, Films, Corrosion rate, Protective films, Chromium, Sulfide films, Oxide films, Iron, Micrography, X-ray spectroscopy, Film formation, Sputter deposition, Samples
Keywords:
13Cr stainless steel, CO2-H2S-Cl− environments, corrosion, stress corrosion cracking, XPS analysis
National Association of Corrosion Engineers
1989
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