Yep, when the federal reserve note goes to zero, coins will still have value as united states money.
I wouldn't think they would go below their melt value.
Pre-1982 pennies, and all nickels, have more metal value than face value.
Quarters and nickles are worth about .06usd in scrap.

I hoard coins because, if you remember, the banks were crying about change not circulating, every dollar of coins in your pocket is a dollar out of the fed's pocket.
If you put it all in nickles and pre-1982 pennies you get some treasury value, too.