What are the main components of metal oxide surface protective film?

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Based on the background of the previous water-cooled reactor system, the main components of the metal oxide surface protective films generated by different commonly used materials in water-cooled reactors are different.: FeCrAl alloy: The core component is dense Al₂O₃, and also contains Fe-Cr-Al spinel oxide, which will form a stable and continuous Al₂O₃ protective layer after long-term service. Austenitic stainless steel/nickel-based alloy: The protective film of austenitic steel is mainly composed of iron-chromium spinel oxide, while the nickel-based alloy forms a chromium-rich spinel-type oxide layer, which has excellent resistance to intergranular corrosion. Zirconium alloy cladding: The oxide film is mainly composed of two crystal forms of zirconium oxide, the monoclinic phase m-ZrO₂ and the tetragonal phase t-ZrO₂, and is the core protective barrier of the cladding. Carbon steel/low alloy steel: The protective film uses Fe₃O₄ (magnetite) as its main component and is a typical iron-based passivation oxide film.