The thickness of the coating is determined according to the contents of the can.
For acid foods, such as asparagus, bamboo shoots in clear water, broccoli, etc., the coating on the inner wall of the tin can can be printed using the "composite coating layer" process. These plants have high protein content. In the process of canning and sealing and heating and sterilization, the sulfur-containing amino saddles have more hydrogen sulfide, which has a strong sulfidation corrosion on the can wall. The "composite coating layer" is the method of "three coatings and two baking" in the printing process. That is, firstly print a layer of base oil with strong adhesion and plasticity based on epoxy resin and xylene resin on the surface of tinplate. After baking and curing, recoat the epoxy resin and phenolic resin coating twice. (The bottom and lid of the can can be turned immediately after the second application). After the "three coatings and two bakings" printing, the total thickness of the coating reaches 10-13 g / m2, which increases the denseness of the coating and the porosity almost disappears. The coating not only has good adhesion, but also has good flexibility and ductility, and has good can-making properties.
(To be continued)