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Corrosion Investigations of Steels in Pb-Bi at FZK J. Konys, G. Müller, J. Knebel

Corrosion Investigations of Steels in Pb-Bi at FZK J. Konys, G. Müller, J. Knebel. Content. Materials Materials and test parameters for corrosion investigation Test equipment Stagnant liquid metal test stand COSTA Liquid metal loop tests Results Corrosion in stagnant liquid lead

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Corrosion Investigations of Steels in Pb-Bi at FZK J. Konys, G. Müller, J. Knebel

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  1. Corrosion Investigations of Steels in Pb-Bi at FZK J. Konys, G. Müller, J. Knebel Content • Materials • Materials and test parameters for corrosion investigation • Test equipment • Stagnant liquid metal test stand COSTA • Liquid metal loop tests • Results • Corrosion in stagnant liquid lead • Discussion of corrosion in stagnant Pb • Differences between corrosion effects in Pb and Pb-Bi • Corrosion in flowing lead • Comparison results obtained under stagnant and flowing conditions • Conclusions

  2. Materials and test parameters for corrosion investigation in lead Stagnant Lead Tests: Materials: 1.4970, OPTIFER IVc, MCrAlY coatings, surface alloyed 1.4970 and OPTIFER IVc, Dimension: small specimens 2 x 10 x 20 mm, Temperature: 550 °C, Oxygen concentr.: 8•10-6 at% Loop Tests at IPPE: Materials: 1.4970, 1.4948, OPTIFER IVc, EM10 Dimension: rods  8mm x 110 mm Temperature: 400 °C and 550 °C Oxygen concentr.: 5•10-4 at% Flow velocity: 2 m/s

  3. alloyed layer bulk 10µm Structure of 1.4970 after surface alloying with Al (GESA treatment ) Cross section of alloyed layer Structure analysis

  4. Stagnant liquid metal test stand COSTA

  5. Conceptual Scheme of CM-2 Lead Loop (IPPE, Obninsk)

  6. Results of tests in stagnant Pb!

  7. Pb corrosion layer bulk material 100 µm 100µm Protective layer formation on steel in lead with controlled oxygen concentration Cross section of the typical structure of a test specimen after 3000 h in liquid Pb at 550 °C. Lead in the upper part contains SiC grains from grinding.

  8. Original and GESA Al-alloyed 1.4970 after 3000 h • in stagnant lead at 550°C and an oxygen content of 810-6 at% Original Al-alloyed by GESA Concentration profiles

  9. Original and GESA Al-alloyed OPTIFER IVc after 3000 h • in stagnant lead at 550°C and an oxygen content of 810-6 at% Original Al-alloyed by GESA Concentration profiles

  10. Pb MCrAlY 100 µm Corrosion Investigation of GESA treated MCrAlY Coating in stagnant Pb after 3000 h at 550°C and an oxygen content of 810-6 at% No measurable corrosion attack after 3000 h!

  11. OPTIFER IVc after 470 h at 550 °C in the gas atmosphere with H2/H2O = 0.4 (= 10-25 bar) element concentration

  12. Structure analysis of OPTIFER IVc after 500 h at 550 °C in the gas atmosphere (H2/H2O = 0.4) OPTIFER IVc OPTIFER IVc Al alloyed by GESA

  13. Structure analysis of 1.4970 after 500 h at 550 °C in the gas atmosphere (H2/H2O = 0.4) 1.4970 Al alloyed by GESA 1.4970

  14. Discussion of corrosion in stagnant lead Growth of spinel and diffusion zone as a function of time at 550 °C Oxide layer formation scheme spinel

  15. Comparison of Pb and Pb-Bi corrosion at 550 °C, 8•10-6 at% Oxygen OPTIFER IVc after 800 h in stagnant Pb-Bi OPTIFER IVc after 800 h in stagnant Pb-Bi OPTIFER IVc after 800 h in stagnant Pb Pb-Bi Pb corrosion layer oxide layer bulk bulk The higher solubility in Bi may cause higher dissolution attack of Pb-Bi. Increase of oxygen activity!

  16. Results of tests in flowing Pb!

  17. 50 µm Exposure to flowing Pb EM 10 3000 h at 550 °C OPTIFER IVc 2000 h at 550 °C 50 µm

  18. EM 10 for 3000 h in flowing Pb at 550 °C

  19. 50 µm 50 µm Exposure to flowing Pb Optifer IVc 2000 h at 400 °C Optifer IVc 3000 h at 400 °C

  20. Exposure to flowing Pb 1.4948 2000 h at 550 °C 1.4948 3000 h at 550 °C 50 µm 50 µm

  21. Exposure to flowing Pb 1.4970 3000 h at 550 °C 1.4970 2000 h at 550 °C 50 µm 50 µm

  22. Exposure of specimens in flowing Pb (IPPE loop) at 550 °C

  23. Comparison of oxide scale growth in stagnant Pb (8•10-6 at% Oxygen) and flowing Pb (5•10-4 at% Oxygen) at 550 °C

  24. Conclusions • Oxide layers can effectively prevent the steel from leaching of the alloy components. • To maintain the oxide layers over long exposure time it is necessary to control • the oxygen concentration in lead. • By this procedure corrosion is changed from that of solution attack to that of oxidation. • Thus, it is needed to find materials that form stable protective oxide scales • under oxygen control in liquid lead. • No corrosion attack at all is observed if Al is alloyed into the surface. • Oxide scale formation in liquid lead obeys the same principle mechanisms • as in controlled gas atmosphere. • There are no principal differences between results of tests in stagnant and flowing lead.

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