Variations in the open-circuit potential, AC impedance, type of semiconductivity, thickness, and chemical composition of oxide films formed on alloy 600 in lithiated water containing dissolved hydrogen were recorded over the 25 to 350°C temperature range. Between 150 and 250°C, each measured property of the oxide film was found to change drastically. Up to about 200°C, alloy 600 exhibited a mixed electrode potential, but behaved as a hydrogen electrode at 250 and 350°C. At 200°C and above, the inner layer of the oxide film was composed of MeO, while the outer layer contained mostly MeOOH or Me(OH)2. AC impedance underwent significant changes above 150°C. Film thickness increased moderately between 25 and 200°C, but more significantly at higher temperatures. At about 250°C, semiconductivity changed from p-type to n-type.

Subject
Composition, Oxide formation, Oxide layers, Impedance, Oxide films, Impedance measurements, Film formation, Sputter deposition, Alloys, Mixed potential, Polarization resistance, Electrodes, Electrode potential
Keywords:
alloy 600, AC impedance, Auger electron spectroscopy, oxide films
National Association of Corrosion Engineers
1990
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