Heat treatment will have a great impact on the corrosion resistance of steel, mainly in the following points:
1. Heat treatment can change the microstructure and grain structure of steel, thereby affecting its corrosion resistance. Generally speaking, a fine and uniform grain structure and a defect-free organizational structure are beneficial to improving corrosion resistance. The coarse grain structure that needs to be wrapped by oxides and the segregated structure will reduce corrosion resistance.
2. Heat treatment can cause changes in the chemical composition and content of steel, which directly affects the corrosion resistance. For example, carbon segregation will occur during the annealing process of carbon steel, which will increase the carbon content on the surface, which will reduce the corrosion resistance. Carburizing and carburizing can form a carbon-rich layer on the surface to improve corrosion resistance.
3. The residual stress generated by heat treatment will also affect the corrosion resistance of steel. For example, the residual compressive stress generated by annealing can improve corrosion resistance, while the tensile stress generated by tempering can reduce corrosion resistance. The effect of stress is more significant on small-grain and high-purity steels.
4. Heat treatment will change the surface state of the steel, such as surface roughness, properties of the oxide film, etc., thereby affecting its corrosion resistance. Generally speaking, a smooth surface and a dense oxide film are beneficial to improving corrosion resistance.
In summary, heat treatment greatly affects its corrosion resistance by changing the microstructure, chemical composition, residual stress, and surface state of steel. Reasonable selection of heat treatment processes and parameters can effectively improve the corrosion resistance of steel.

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