[sammyg2]

What type of coating is it? Many times on exhausts they use an aluminium-oxide type of coating and call it ceramic.

We have boron-duffusion coating done to machine parts faily often for erosion resistance, it makes the parent metal very, very hard but the coating is only a few mils thick. I'd be interersted to see if they use the same process.

If it's the same as what I'm familiar with, basically they clean a part and put it in an oven and gradually take it up to a prescribed temperature, then introduce a hot vapor of a desired metal or substance and allow the hot vapors to permeate the object and stick at the molecular level and then they do a controlled cool down.
The prep, the time in vapor, the temperature controls, all affect the quality of the coating.

Damn, now I might have to do research today instead of watching Andy Griffith.