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Powder coat melts at 400 degrees. Not good on exhaust system stuff.I'd recommend blasting the parts and coating them in Norrells moly resin. That gets baked at 350 degrees and is then resistant to even higher temps. It is made to finish guns and is very durable. Comes in many colors too. Totally chemical resistant too. Acetone just cleans it. Only way to remove it is blasting.I keep a bottle of semi gloss black in the shop to do small parts with.