Product News

What causes tin cans to rust?

June 20 , 2023

What kind of material is tinplate? It is actually a kind of steel. Under normal circumstances, the surface of iron exposed to the air will have active chemical properties, oxygen in a humid environment will continue to oxidize with water in the air, that is to say, iron in contact with the air will react chemically with oxygen in the air, when the oxygen in the air is dissolved in water, the molecules on the surface of iron will be transformed into iron oxide, which is what we often say is rust. That's why iron rusts. 



1, often contact with water or long-term in the air humid environment.

2. The exterior protective layer is damaged or scratched.

3. Contact with corrosive substances.


All kinds of iron boxes and cans of iron materials are easy to rust because of improper use, storage or other reasons, which affects the appearance and overall performance. But the tin made of tinplate is a special case, some tinplate box finished products will be tinned and coated with anti-rust gloss before printing, coupled with the protection of ink, the tinplate has been cut off from the air, and rust will not occur easily under normal use.


Doesn't the production of iron cans mean that the surface has been coated with light oil? Isn't that what the varnish does to prevent rust? Yeah, why would an iron can with protective gloss still rust?   Here's why:


1. Tinning and glazing on the surface of tinplate can effectively prevent rust. However, some smaller manufacturers have not established a complete set of quality management system. In the production process, due to the improper operation of the workers, the scratch was caused, and the protective layer of the light oil was scratched, so the broken part will chemically interact with the oxygen in the air.


2. The problem of matching the tightness between the lid and the body of the tin can. In general, in order to prevent moisture in the internal products, the tightness will be tighter. Every time after opening the lid to take out the food, then close the lid, the contact surface between the lid and the can body will be worn, the more times the lid is opened, the greater the wear surface will be, the longer the time, the protective layer of the contact surface will be erased. Therefore, this wear surface will also have the possibility of rust.




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