According to the characteristics of the contents, packaging containers made of tin plate strip usually need to be coated with a certain coating on the inner surface of the container to prevent the contents from eroding the container wall and contaminating the contents, which is conducive to long-term storage. For tin plate strip candy boxes, in order to prevent post-processing curling and exposed tin bottom tin plates from scratching and rusting, a layer of decorative coating is also needed to increase the appearance. For the performance of coatings in food cans, not only have corrosion resistance, good adhesion, flexibility, non-toxic, odorless, meet food hygiene and safety requirements, but also have post-processing such as high-frequency resistance welding heating, internal repair coating Local high temperature heating, and high temperature cooking at 121 ℃ after canning without discoloration and loss of light. Generally, phenolic resin coatings, epoxy-phenolic resin coatings, acrylic resin coatings, and aluminum powder coatings are coated on the tin plate cap inside. Usually, the type of coating and thickness of the coating are selected according to the characteristics of the contents.