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Passivation usually requires the use of phosphate or chromate to treat the substrate, and the passivation methods mainly include spray type, immersion type, and coating type. With the increasing demand for uniformity of coating by users and the increasing attention paid to environmental protection, coating passivation methods have attracted great attention. The coating type passivation uses the roller coating method to apply the treatment solution to the surface of the strip steel, forming an isolation film between the metal and the coating. By using this method, the passivation process is easy to control and the film thickness is uniform, while there is little or no waste liquid, which is beneficial for environmental protection.