I have ceramic coated..twice.
First time was a chrome type finish.
It lasted 4 years.
Second time was a black "turbo" finish as above. (Still going well after 3 yrs)
This black finish will handle higher temps but the Rotax exhaust pushes the limits of it, as it is thin walled and gets hotter than comparable auto exhausts.
I do not think it reduces radiated heat. I applied it to reduce rust/corrosion and for "looks".
It is far far cheaper to ceramic coat every 5 years or so than replace the exhaust.....
Cost for all pipes and muffler, about $200 usd.....blasting/priming/top coat.