Question regarding food expiration

[Moony]

I work in the (drinks) canning industry and can tell you all our cans (aluminium now, though we used to use steel ones as well in the old days), are coated with a 'lacquer' inside and out to prevent corrosion. The drink we can are also high in acids and the lacquer prevents this from literally eating through the body of the can while it sits on the shelf.

Dents in cans are a problem for 2 reasons.

1) They can cause the lacquer (inside or outside) to 'peel off' or blister, thus removing some of the protection it provides and increasing corrosion. If it's the internal lacquer obviously this will also be floating around inside the drink - though it won't poison you it isn't exactly ideal...

2) The cans are made air-tight with a lid which is bent carefully into shape around the rim, they aren't welded. So if the can gets dented it can push this seal out of shape and allow air in / your food to leak out. Typically this will only be a porblem with very bad dents or those near the rim of the can.