Tinplate tin plating effec
* 来源: * 作者: tinworld * 发表时间: 2019/03/26 9:32:45 * 浏览: 592
Tinplate tin plating effect
Q:
Canned food is mostly made of tinplate, but why should it be tinned on both sides of the iron?
For the protection of food, please explain with chemical knowledge.
What if the tin plating on the outside is damaged?
A:
Best answer: Iron exposed to the air reacts with oxygen and water vapor in the air to form rust (Fe2O3•xH2O).
The cans of metal cans are made of iron sheets, and in order to prevent the metal pieces from rusting, a layer of tin is plated on the pieces of iron. The tin layer separates the iron sheet from the oxygen and water vapor in the air. Since the iron piece is not exposed to oxygen and water vapor in the air, the iron piece does not rust. Therefore, the tin plating is to prevent the iron sheet from rusting and indirectly protect the food in the tank, rather than any direct effect on the food in the tank.
However, there is a big disadvantage in that it is rust-proof by plating a tin layer. Since tin is less active than iron, when tin plating is damaged, a small part of iron is exposed to the air, iron is preferentially corroded (ie, rusted), and the rate of iron rust is lower than that of tin without tin plating. Much faster.
Although tin plating has the above disadvantages, tin and its compounds are not toxic. Since the food contained in the tank is food, it is safe to avoid poisoning when eating or tin plating. Other metals that are often plated on iron sheets to prevent rust, such as zinc and aluminum, are somewhat toxic.
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