Composition and morphology of oxide films formed on PT-7M titanium alloy in high temperature water

• S.N. Orlov^1,2, N.A. Glukhoedov¹, A.A. Zmitrodan³, O.N. Pestova¹, A.S. Mereshchenko¹, N.A. Bogachev¹ and M.Yu. Skripkin¹

¹ Institute of Chemistry, Saint-Petersburg State University, 7/9 Universitetskaya Embankment, 199034 St. Petersburg, Russian Federation
² Institute of Nuclear Industry, Peter the Great St. Petersburg Polytechnic University (SPbPU), 29, Polytechnicheskaya Street, 195251 St. Petersburg, Russian Federation
³ Federal State Unitary Enterprise “Alexandrov Research Institute of Technology”, 72, Koporskoe Shosse, 188540 Sosnovy Bor, Russian Federation

Abstract: The structure of the oxide film on PT-7M titanium alloy used in the construction of the first circuit of Russian small nuclear power plants (SNPP) is considered. The experiment was carried out in stainless-steel autoclaves with PPL liners at a temperature of 240°C. Deoxygenated water and solutions containing salts of metals that are components of stainless steel were used as the aqueous phases. Samples of titanium alloy after heating in autoclaves were examined by high-resolution X-ray diffraction and X-ray fluorescence analysis and by scanning electron microscopy. According to the results of the study, the oxide film consists of a crystalline modification of titanium dioxide – anatase – and includes two layers: a dense one consisting of neat titanium dioxide and a loose one, which may include corrosion products of steel. A film with a thickness of about 100–120 nm is formed after 24 hours of the experiment and reduces the rate of titanium influx into the aqueous phase. After 336 hours (14 days) of heating, the thickness of the solid film is about 200 nm, while the sizes of the crystallites that make up the loose layer are 0.5–4 μm.

Keywords: titanium alloy, first circuit, protective oxide film, small nuclear power plants

Int. J. Corros. Scale Inhib., 2023, 12, no. 3, 1275-1291
doi: 10.17675/2305-6894-2023-12-3-26

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