I have been running stainless steel header pipes on my BMW Airhead for years, and a stainless steel muffler on my VFR800 also for years. Looks like chrome. No corrosion, no rust, no polishing needed. Never.
The BMW headers do go a light straw colour around the first bend where the heat is, but it is a lot less discoloration than chrome turning blue in the same situation.
Almost all BMWs end up with full stainless pipes and mufflers because they rot the chrome systems out even quicker than Honda Fours.
You can get stainless steel in a variety of grades, each with varying amounts of nickel and chromium in the steel to make it "stainless". The cheaper, lower grades are more prone to a little discoloration. But the higher grades polish up like chrome and stay that way forever.
Clear coating stainless would be pretty much a waste of time.
Stainless muffler on my VFR after 10 years use:
And Aussie company makes all their pipes and mufflers out of stainless, with no clear coat ever needed.
http://www.staintune.com.au/This is what they say they use:
"All Staintune products and hardware are made from 304 grade stainless steel which is one of the most durable materials to use and is impervious to all kinds of corrosion. 304 grade stainless steel can be polished to a mirror-like finish. Because of the nature of 304 stainless steel, at any stage of the product's life it can be buffed back to a deep as-new glow. Staintune motorcycle exhausts are made to outlast the competition. "