Mechanisms for formation and disruption of surface oxides: Final report

Technical Report · Sat Aug 01 00:00:00 EDT 1987

OSTI ID:6049223

Lumsden, J B

Mill-annealed alloys 600, 690 and 800 were exposed to 10 and 50% caustic solutions containing 1% Na/sub 2/CO/sub 3/ to initiate IGA. IGA reproducibly occurred in all three alloys in the 10% caustic solution at 350/sup 0/C after a 240 h exposure and in the 50% caustic solution at 320/sup 0/C after a 120 h exposure. Reproducible IGA did not occur in the 10% caustic solution at 320/sup 0/C after a 120 h exposure. IGA was not observed in mill annealed plus thermally treated alloys 600 and 690 after exposure to any of the test conditions. IGA initiation was correlated with a dealloying mechanism in which the more active alloying metals, iron and chromium, selectively dissolve. Boric acid and calcium hydroxide additives were found to slow or prevent IGA by inhibiting dealloying. Titanates prevented IGA in alloys 600, 690 and 800, passivating the surface with a nickel titanate film.

• Research Organization: Rockwell International Corp., Thousand Oaks, CA (USA). Science Center; Electric Power Research Inst., Palo Alto, CA (USA)
• OSTI ID: 6049223
• Report Number(s): EPRI-NP-5368; ON: TI87920566
• Country of Publication: United States
• Language: English

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