Technically, you won't find it at all because electrical area classification is for the purpose selecting and installing electrical equipment only. This doesn't mean you don't have a valid concern, simply that specifying shop prime coats is out of electrical area classifications scope.
In your case, the key is knowing why the area is classified in the first place; i.e., what flamable material is present that leads to classifiying the location. You will then need to review the reactance and concentration of the material against the prime coat.
The odds a very high that there will be no effect at all, but it is worth the minor review to assure yourself.