What material is tinplate

Tinplate is a type of alloy that we often refer to now. The chemical properties of alloys are very good, and they can combine the advantages of two or more metals. Tin has stable chemical properties and is not easily corroded. Iron has unstable chemical properties and is prone to oxidation, but it has high hardness and good formability. People often coat tin on top of iron sheets to prevent rusting. This type of tin clad iron sheet is commonly known as "tinplate". One ton of tin can cover over 7000 square meters of iron sheet, so tinplate is very common and cheap. The customer of tinplate is the canning industry. If protected, tinplate can be used for more than ten years without rusting. However, once the tin "clothes" are accidentally damaged, the iron sheet is quickly corroded (electrochemical corrosion), and soon the entire sheet of tinplate is covered with reddish brown rust spots. So, when using tinplate, care should be taken not to damage the tin layer, nor to let it get damp or heated. Before liberation, due to imperialist aggression, our country had to rely on foreign imports for even tinplate. The name "tinplate" is derived from the fact that it was imported from Makou in Ali, Xizang (from Makou in Britain via India).

[Tinplate - Characteristics and Advantages]

1. Opacity. In addition to causing food deterioration reactions, light can also cause changes in proteins and amino acids. Vitamin C is more likely to interact with other food ingredients when exposed to light, resulting in significant loss. According to research analysis, the loss of vitamin C in transparent glass bottles of milk is 14 times higher than that in dark bottles. Light can also cause milk to produce oxidative odors, as well as the breakdown of nuclides, methionine, and other nutrients, resulting in a loss of nutritional value. The opaque nature of tin cans increases the retention rate of vitamin C.

2. Good sealing and the barrier properties of packaging containers to air and other volatile gases are crucial for the preservation of nutritional content and sensory quality. Comparing various fruit juice packaging containers proves that the oxygen permeability of the container directly affects the browning of fruit juice and the preservation of vitamin C; Metal cans, glass bottles, aluminum foil adhesive layers, and paper boxes with low oxygen permeability have better preservation of vitamin C, among which iron cans are used.

3. The reduction effect of tin, the tin on the inner wall of the tinplate will react with the oxygen remaining in the container during filling, reducing the chance of food components being oxidized. The reducing effect of tin has a good preservation effect on the flavor and color of light colored fruits and juices. Therefore, juice cans packaged in unpainted iron cans have better nutritional preservation than juice cans packaged in other materials, with slight brown changes and better acceptance of flavor quality. As a result, the storage period is extended.

4. Provide an effective source of iron. Tin cans are used to store food, and except for a few light colored fruit and juice cans, most empty cans with internal paint are used to improve the corrosion resistance of the container; Due to the electrochemical effect of metals, a small amount of iron will dissolve from canned food during storage, existing in the form of divalent iron in sealed canned food, which is easily absorbed by the human body, with a content of about 1 to 10 ppm. In terms of fruit and vegetable products, the raw materials themselves do not contain much iron. For iron can products, if the iron content is calculated as 5 ppm per 350 ml beverage can, each can can can provide 1.75 mg of iron, which is about one tenth of the daily intake of 18 mg for the human body. If the above-mentioned fruit and vegetable juice beverage cans contain abundant vitamin C, iron is more easily absorbed. Therefore, iron canned food and beverages are a good source of iron, and their nutritional significance for iron canned food is even more profound. Due to these properties, tin cans provide a closed system that completely isolates environmental factors in addition to heat. They prevent colored foods from deteriorating due to light, oxygen, and moisture, and do not become lighter due to the transmission of fragrance or contamination by environmental odors. The stability of food storage is better than other packaging materials, and the retention rate of vitamin C is high, as well as the preservation of nutrients.