Unless you drive it through a giant shredder, it shouldn't be inflammable. All metals want to revert to their ores or oxides - steel/iron rusts, ally and mag do the same but at higher speeds especially when finely divided. Sheet metal and cast shapes should be fine.
At least you'd know straight away, unlike the new Chevrolet Volt which keeps you guessing for three weeks after a crash and then goes up........
http://www.autoblog.com/2011/12/07/house-to-hold-investigative-hearings-on-chevy-volt-fire-silence/ 
