I got the cylinder barrel and exhaust ceramic coated. After a couple of hundred miles, I could scrape the coating from the barrel with my nails. The exhaust was rustier than it had been. 
I took the bike back to show them. I stripped the parts off and they recoated them. 
Less than a year later, the barrel is still fine, but the exhaust is a mess again. They said that they will do the exhaust again. 
Has anyone else had any experience with Ceramic coating, I think it is called Cerakote. 

At this point, I have only used VHT Ceramic coating which comes in a spray can. You can get the VHT exhaust coating by the quart and spray with a gun, but I have not did that yet. Mine has held up OK, I have done a turbo but have yet to put it back on the bike to see how it holds up. The clean, prep, spray, and cure process is very important. If not done properly, durability will not be achieved.

I have researched Cerakote, and seen some finished product in car shows and such. It is very durable. However, it is even more important with Cerakote to follow the application process. It has a very high oven cure temperature and most standard ovens can not reach that temperature, so the person doing the application has to have all the right equipment.

Also, there are a few different classes of Cerakote. Some is air dry, Some is low temperature cure, and some is the very high temperature cure. Are you sure that that they are using the proper version of CERAKOTE for your exhaust? At this point, based on what you have said, I am more inclined to believe that the business doing the coating is either not using the right product for your exhaust and/or is not following the manufacture application process.

If they are, you should contact the CERAKOTE company directly and see if they have an explanation why the coating is not holding up.

I have used lots of Cerakote coatings. I used silver Ice on a set of Aprilia tuono exhaust which glowed red and got white hot under sustained acceleration ( which i did quite allot of ).It made a scruffy stock badly stained stainless pipe stand out and look really nice and suffer no deterioration.
 
I had it on my TDR 250 cases, two which were plastic , as everything else i used migrated South at the first sight of any petrochemical products . I thought the finish was okay by comparison but only for a road bike as compared to the finish on the exhaust, it was dull and textured finish. However, neither failed despite relentless sustained heat and weather.
Don't know why the finishes come out that way, one obviously smooth and shiny and the other has to be flat and shot prepped surface.
I would be taking them back to the people who applied it and asking them to redo the parts as the finish is supposed to be guaranteed from deterioration. That's it's selling point.