Steve beat me to it. Always-ALWAYS clean first. Any contaminant on the surface can be driven into the metal's pores by abrading, whether it's sandblasting or sanding. Once it's in the pores it can be difficult to get out. You've just learned a lesson you'll remember for a lifetime.
Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.
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