1. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Corrosion Investigations of Steels in Pb-Bi at FZK J. Konys, G. Müller, J. Knebel 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 Content

2. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 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.:810 -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.:510 -4 at% Flow velocity: 2 m/s

3. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Structure of 1.4970 after surface alloying with Al (GESA treatment ) 10µm bulk alloyed layer Cross section of alloyed layer Structure analysis

4. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Stagnant liquid metal test stand COSTA

5. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Conceptual Scheme of CM-2 Lead Loop (IPPE, Obninsk)

6. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Results of tests in stagnant Pb!

7. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 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. 100 µm bulk material corrosion layer Pb

8. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 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. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 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. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 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% 100 µm MCrAlY Pb No measurable corrosion attack after 3000 h!

11. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft OPTIFER IVc after 470 h at 550 °C in the gas atmosphere with H 2 /H 2 O = 0.4 (= 10 -25 bar) element concentration

12. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Structure analysis of OPTIFER IVc after 500 h at 550 °C in the gas atmosphere (H 2 /H 2 O = 0.4) OPTIFER IVcOPTIFER IVc Al alloyed by GESA

13. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Structure analysis of 1.4970 after 500 h at 550 °C in the gas atmosphere (H 2 /H 2 O = 0.4) 1.4970 1.4970 Al alloyed by GESA

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

15. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Comparison of Pb and Pb-Bi corrosion at 550 °C, 810 -6 at% Oxygen OPTIFER IVc after 800 h in stagnant Pb-Bi OPTIFER IVc after 800 h in stagnant Pb The higher solubility in Bi may cause higher dissolution attack of Pb-Bi. Increase of oxygen activity! Pb-BiPb bulk corrosion layeroxide layer

16. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Results of tests in flowing Pb!

17. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Exposure to flowing Pb EM 10 3000 h at 550 °C OPTIFER IVc 2000 h at 550 °C 50 µm

18. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft EM 10 for 3000 h in flowing Pb at 550 °C

19. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Exposure to flowing Pb Optifer IVc 3000 h at 400 °C Optifer IVc 2000 h at 400 °C 50 µm

20. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Exposure to flowing Pb 1.4948 3000 h at 550 °C 1.4948 2000 h at 550 °C 50 µm

21. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Exposure to flowing Pb 1.4970 3000 h at 550 °C 1.4970 2000 h at 550 °C 50 µm

22. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Exposure of specimens in flowing Pb (IPPE loop) at 550 °C

23. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Comparison of oxide scale growth in stagnant Pb (810 -6 at% Oxygen) and flowing Pb (510 -4 at% Oxygen) at 550 °C

24. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 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.