Comment Re:Better rescue the coke machine (Score 5, Informative) 269
True. Most metal cans (the kind used for packaging, anyway) are coated with a layer of plastic to prevent interaction with the Al/Sn in the metal of the substrate itself. Particularly with acidic contents (tomatoes are the ones that come most readily to mind.) Can *ends* are manufactured separately and joined to the can bodies themselves after filling. Some can ends are coated with plastic over the majority of the surface, but others have perforations and other 'gaps' that allow for proper sealing/seaming between the can and the can end, and for tabs to break through, etc. Any place the plastic coating is missing and an acidic ingredient can come into contact with the metal, corrosion can occur (though slowly).
Source: I'm a market researcher specializing in food/beverage packaging in the US.
Source: I'm a market researcher specializing in food/beverage packaging in the US.