Where did this misconception come from? stainLESS steel... NOT stainPROOF steel. sufficient heat, caustic, or oxidizing substance will cause deterioration. While stainless steel is far more resistant to oxidation than "carbon" steel, if subjected to 1000+ degrees, and a blast of oxygen, sulpher, NOx... plus a few unburned hydrocarbons... it will rust. The headers on my drag boat are stainless steel... they will last 1 season... about 25 minutes of running... before oxidation eats holes in them... Our 15+ year old exhaust systems are going to show some rust. It's a credit to JZD that they lasted this long.