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To clarify the corrosion control effect of Zn injection into hydrothermal environments, the oxide films on Alloy 690 in the deaerated borated and lithiated water have been investigated using potentiodynamic polarization curves, electrochemical impedance spectra at 300 degrees C and ex-situ X-ray photoelectron spectroscopy. With Zn injection in the solution, ZnCr(2)O(4) and ZnFe(2)O(4) were formed in the inner and outer layers of the oxide films on Alloy 690, respectively, through exchange reactions between Zn(2+) and Fe(2+)/Ni(2+). A simple model for oxide film structure change and the mechanism of corrosion inhibition by Zn injection is proposed and discussed. (C) 2011 Elsevier Ltd. All rights reserved.