Hmm. I've never used Cerakote but been told it's the biz for calipers etc as it's thin but really tough. Popular with the gun crowd.
Maybe there's different grades under the same name, or its hard to apply correctly? but I guess time will tell what is the real story.
I'm currently getting a bunch of stuff done in powder for our military grade products. There is a lot said about powder but the truth is always a bit more complex. It is an industrial coating so getting a consumer grade finish is difficult. Many places will coat your stuff in an open plant next to garden furniture and wrought iron gates. Grit can be introduced in the oven.
That said for cases they don't have to be perfect and the masking is easy, however be clear what you want masked as you will be unhappy if you can't fit the water pump anymore.
Durability is a factor of preparation. Stories of it flaking off are due to oil contamination. But consideration should be given to the chromate conversion. Older non Rohs treatments were more tolerant and keyed better. Newer friendly versions can work well but cleaning process is far more involved if you want good adhesion. I've seen people try to just swap treatments with no other changes and paint flaking becomes an issue. One that many customers probably don't care or notice.
Cases would need some real good cleaning as thread holes can bleed oil in the oven which will cause blotches and adhesion issues. I wonder how porous cast magnesium alloy is?
Your painter may deal in motor parts and armed with a few sharp questions you should be able to work out if they are the chaps for you or to try someone else.
But then again, maybe don't listen to me, I seem to have a history of misinformation.
