Has anyone done a Cerakote finish right over a part that is finished in Black Phosphate? I want to refinish a linear muzzle brake that has a rough finish and I was wondering if this could work. 
 

Thanks in advance for any advice 

I’m not 100% - but I think they’ll strip the existing finish from the part before applying cerakote.

It's recommended to sand blast phosphated parts for 3-5 seconds then thoroughly clean with acetone before applying Cerakote.  The part does not need to be stripped down to bare metal.  The paint will stick to the phosphate, but the problem is with poorly applied phosphate coating flaking off, causing the Cerakote to flake off, causing many calls to Cerakote's customer support line.

4 hours ago, Scorpio64 said:

It's recommended to sand blast phosphated parts for 3-5 seconds then thoroughly clean with acetone before applying Cerakote.  The part does not need to be stripped down to bare metal.  The paint will stick to the phosphate, but the problem is with poorly applied phosphate coating flaking off, causing the Cerakote to flake off, causing many calls to Cerakote's customer support line.

I was imagining something like this, it makes sense. Thank you for your tip!