The type of tinplate coating must be selected according to the contents of the can.
Phenolic resin coating: It has good coverage and has excellent corrosion resistance to chemicals. It has blocking properties against sulfide ions and cannot penetrate the coating, and is suitable for meat can, fish can, vegetables can,soups can. However, the adhesion to the tinplate surface is poor, especially when the thickness of the coating is greater than 3 to 4mm, the flexibility of the coating is poor. Its baking temperature generally does not exceed 190 ° C, otherwise the paint penetrates into the substrate through the pores of the tin plating layer and undergoes thermal degradation.
Sulfur-containing compounds occur naturally in animal and plant foods. During the hot processing of cans, these compounds will decompose to produce free sulfide and hydrosulfide ions, and will release hydrogen sulfide, forming sulfur spots on the abraded part (mechanical injury) of the inner wall of the can. When the pH value of hydrogen sulfide is less than 6, it will cause the iron sulfide at the top gap in the tank to fall off and pollute the contents of the can.