A method for mitigating recontamination of a decontaminated carbon steel surface in a water-containing system or component of a nuclear reactor, comprising: performing decontamination of an oxide-containing carbon steel surface in the water-containing system or component, comprising: removing the water-containing system or component from operation; adding to the water-containing system or component a decontamination solvent to contact the oxide-containing carbon steel surface, the decontamination solvent comprising a chelating agent; and removing oxide from the oxide-containing carbon steel surface to produce the decontaminated carbon steel surface; following the decontamination and prior to returning the water-containing system or component to operation, using the decontamination solvent that is remaining from the decontamination in a subsequent passivation process; conducting the passivation process, comprising: cooling the water-containing system or component and the decontamination solvent to a passivation temperature of about 60°C (140°F) to 71°C (160°F); adding caustic and oxidant to the decontamination solvent remaining to form a passivation solution; inducing passivation of the water-containing system or component with the passivation solution; and forming a passivation film on the decontaminated carbon steel surface; returning the water-containing system or component to operation; and as a result of the passivation film, reducing the re-growth of oxide on the decontaminated carbon steel surface, wherein the chelating agent is present in an amount that constitutes from about 0.5 g/l to about 2.0 g/l of the passivation solution. performing decontamination of an oxide-containing carbon steel surface in the water-containing system or component, comprising: removing the water-containing system or component from operation; adding to the water-containing system or component a decontamination solvent to contact the oxide-containing carbon steel surface, the decontamination solvent comprising a chelating agent; and removing oxide from the oxide-containing carbon steel surface to produce the decontaminated carbon steel surface; removing the water-containing system or component from operation; adding to the water-containing system or component a decontamination solvent to contact the oxide-containing carbon steel surface, the decontamination solvent comprising a chelating agent; and removing oxide from the oxide-containing carbon steel surface to produce the decontaminated carbon steel surface; following the decontamination and prior to returning the water-containing system or component to operation, using the decontamination solvent that is remaining from the decontamination in a subsequent passivation process; conducting the passivation process, comprising: cooling the water-containing system or component and the decontamination solvent to a passivation temperature of about 60°C (140°F) to 71°C (160°F); adding caustic and oxidant to the decontamination solvent remaining to form a passivation solution; inducing passivation of the water-containing system or component with the passivation solution; and forming a passivation film on the decontaminated carbon steel surface; cooling the water-containing system or component and the decontamination solvent to a passivation temperature of about 60°C (140°F) to 71°C (160°F); adding caustic and oxidant to the decontamination solvent remaining to form a passivation solution; inducing passivation of the water-containing system or component with the passivation solution; and forming a passivation film on the decontaminated carbon steel surface; returning the water-containing system or component to operation; and as a result of the passivation film, reducing the re-growth of oxide on the decontaminated carbon steel surface, wherein the chelating agent is present in an amount that constitutes from about 0.5 g/l to about 2.0 g/l of the passivation solution.