Abstract: The in-service chemical decontamination of reactor systems, equipment and components is essential for reducing individual and collective dose levels, which can compensate for the shortcomings of conventional radiation protection measures. The optimized chemical decontamination process was quickly selected by Cr-substituted magnetite oxide dissolution test and pre-oxidized film corrosion test. The decontamination factor is 3.08 in the practical application of the test in decontamination of a nuclear power plant primary loop elbow, while the corrosion depth of Z2CN18-10 base metal is much less than 1 μm.