If it is actually "tin" rather than aluminum - beware. It will not weather well, and you will have extremely large amounts of metal contaminants in your water. Most tins like you mention are food grade, which means the tin plating over the steel will not rub off on your food... but that's not considering adding heat and liquids. Over time (and likely not much time) the heat applied will cause a separation of the tin plating from the steel underneath. As soon as that happens, you'll have rust everywhere.
But then, maybe it's aluminum. Distinguishing between the two can be awfully difficult. I suppose, if, for $0.50 you can get another you might want to cut it or drill some holes through it and submerge it. Let it sit outside for a while an see what happens.