I don't ride much in the rain.. even if I do I could care less about the exhaust headers when I'm riding in the rain, I worry about staying upright on two wheel more.
I've had similar finish on the header pipes of my 1989 Honda CB-1 since Oct. 2003, some 13,000 miles ago. I've ridden my CB-1 in downpooring rain, salted roads, dirt/gravel roads, nothing seem to fade the finish of ceramic coated exhaust headers.
Besides, I've got two sets of header pipes now, if it does go bad because of water, I've got another set of headers to put back on.
Master your environment, and you will survive just fine.
Chances favor the prepared mind.