Hi Ed! - My muffler is stainless and although it will discolor to a brownish color, I've seen zero rust/corrosion. I'm in mid-east Tennesse, and we have rather mild winters, but plenty of rain and humidity. My 750 is hangared and I have a preheater (very low output electric heater with fan) on a timer that blows warm, dry air up into the cowl each a.m., so everything stays dry, the oil and battery are warm, and it cranks instantly on the worst winter day! I suppose that would keep any corrosion down, too.