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Characteristics of oxide films formed on 304 stainless steel under alternately changing Ni(2+) concentrations in oxygenated high temperature water were examined. Oxides preformed under low Ni(2+) concentration evolve from hematite to spinel after subsequent immersion under high Ni(2+) concentration. Meanwhile. Ni content in the surface layer of oxide rises up while Fe content drops. Oxide films preformed under high Ni(2+) concentration show little change in phase composition after subsequent immersion under low Ni(2+) concentration. Fe contents in surface layer rise up while the change of Ni contents depends on the original phase composition and whether residual Ni(2+) is present. (C) 2011 Elsevier Ltd. All rights reserved.