Some foods require some tin in the can to dissolve and form free tin ions to maintain the appearance and flavor of the food in the can. Without free tin ions, the color of light-colored foods tends to be dark, and the color of green vegetables will change. In the state of lack of oxygen in the can, tin ions and food produce tin-chromium compounds to remove sulfides in the food. These effects will enable canned food to be stored, sold, and eaten for a long time.
Tin can is dissolved in canned food, so the thickness of the coating on the inner wall of the tinplate can is generally between 3.5 and 6.0 g / m2. Within this thickness range, the coating has a certain porosity. The liquid in the can content penetrates the surface of the tin layer through these pores, and the tin is slowly dissolved to form tin ions, thereby achieving the purpose of extending the shelf life of the can.