fire extinguisher powder removal

does anyone have a suggestion on getting aluminun and crome back to a normal appearance after using a fire extinguisher. White specs on crome does not want to come out have tried cleaners and also polish does not work very well

 

you let it set to long after we have been on fire we wash everthing the stuff in the bottles seems to eat at the metal..Dave

 

as the engine cools down
safe enough not to ignite up from headers
soak down with wd 40
wash and clean when back at shop/worked for me