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Influence of H2S on the localised corrosion of 316L stainless steel: Part 1 - Coupon testing

Hesketh, J; Dickinson, E J F; McMahon, G; Martin, M; Turnbull, A; Hinds, G (2020) Influence of H2S on the localised corrosion of 316L stainless steel: Part 1 - Coupon testing. NPL Report. National Physical Laboratory. MAT 92

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Corrosion coupon immersion tests were performed on 316L SS in 50,000 ppm Cl- at 110 ºC to evaluate the effect of partial pressure of H2S on pit depth and density in a simulated oilfield
environment. The protective film formed in these environments was analysed by nanoSIMS and shown to consist of mixed metal sulphides and oxides, the former being considered to enhance chloride ion uptake leading to more ready passivity breakdown and pit initiation. H2S is deduced to be acting primarily as a chemical agent in supporting subsequent pit propagation, adsorbing on the pit surface and constraining the repassivation process. Pitting was most severe at intermediate partial pressures of H2S. At more elevated partial pressures, pitting was inhibited, which is attributed to blocking of the pit surface by dense sulphide phases that limited access of H2S to the pit surface. Surface finish was shown to be a critical factor in pit development with specimens machine-ground to a Ra< 0.2 µm showing extensive pitting but with specimens hand-ground to a P1200 finish (Ra<0.1µm) showing very limited pitting.

Item Type: Report/Guide (NPL Report)
NPL Report No.: MAT 92
Keywords: stainless steel, pitting corrosion, oil and gas
Subjects: Advanced Materials > Corrosion
Divisions: Electromagnetic & Electrochemical Technologies
Publisher: National Physical Laboratory
Identification number/DOI: 10.47120/npl.MAT92
Last Modified: 08 Jan 2021 15:33
URI: http://eprintspublications.npl.co.uk/id/eprint/9005

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