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I. Core Functions and Objectives: The metal chemical oxidation treatment for water-cooled reactor systems aims to form a stable and dense protective oxide film on the metal surface, thereby significantly reducing the corrosion rate of materials in high-temperature and high-pressure water environments. It also helps to minimize the release of corrosion products into the coolant, while suppressing the increase in the radiation field caused by activated corrosion products, thus ensuring the long-term safe and stable operation of the reactor. II. Principle of oxide layer formation: In the high-temperature water environment of water-cooled reactors, structural materials such as stainless steel and zirconium alloys undergo a controlled oxidation reaction between the atoms on the metal surface and oxygen in water, resulting in the formation of an initial oxide layer ； Subsequently, through the regulation of hydrochemical conditions (such as hydrogen reduction and oxygen passivation), a dual-layer oxide film is gradually formed: the outer layer consists of a porous iron-based oxide, while the inner layer is a dense chromium/zirconium-based oxide, which effectively prevents corrosive agents from penetrating into the substrate. III. Typical Processes and Control Methods: Hydrogen reduction process – Hydrogen at a concentration of around 1.25 mg·kg⁻¹ is injected into the coolant to suppress the dissociation of water and the formation of free oxygen, thereby facilitating the stable growth of an oxide film in an environment with low dissolved oxygen levels. This is the mainstream method for film formation control in pressurized water reactors. Oxygenation passivation condition: The dissolved oxygen level is controlled at a specific stage; dissolved oxygen is utilized to promote rapid passivation of the metal surface and the formation of a uniform oxide film, which is suitable for film formation treatment of certain candidate materials for supercritical water-cooled reactors. Zinc injection process: Zinc ions at a concentration of 5–35 μg/L are injected into the primary loop coolant to replace the cobalt and nickel ions in the existing oxide film, thereby forming a stable zinc-containing protective layer that can reduce the overall dose to the system by more than 20%.