[en] The pre-oxidation condition with low concentration of nitric acid permanganate and conventional high concentration alkaline permanganate for steam generator material Inconel 690 and 600 oxidation decontamination is discussed. Experiments in three parts have been performed. They are chromium release, measurements of corrosion potentials and polarization curves in NP and AP solutions for Inconel 690 and 600. The results show that AP is more effective than NP at releasing chromium from Inconel 600 oxides while the reverse applies to Inconel 690 oxides. The corrosion potential of Inconel 600 moves in a positive direction when the acidity becomes high NP while the reverse occurs for Inconel 690 and corrosion increases when the acidity and alkalinity becomes high as can be seen from polarization curves of Inconel 690 and 600 in NP and AP