[Archie T. Hogan]

Seems that the chemical in an A B C class fire extinguisher contains,

"monammonium phosphate"

which is "highly corrosive to aluminum".

Should one be discharged ,

it "flows into cracks an crevices and can't be washed out".

"To avoid corrosive destruction, the vehicle must be disassembled to manually clean the surfaces right down to the rivets."

advice is a B-C type extinguisher ,

the chemicals can be washed out.