The powder in an A,B,C type
extinguisher is very corrosive and difficult to remove from cars once
applied. That's where there is additional damage in the long term through
rust.

Bjorn,
corrosive to an aluminum engine?
any idea which stuff would be affected most?
(yikes, copper wires!)
any idea what it takes to clean an engine up after using an ABC in there?

thanks,
Bill