a good powdercoater will not only tank it to clean but also dip it for a zinc phosphate coating. My brother is a coating engineer and he has lots of experience with powdercoating systems and development and for a top notch result it's the best way to go. Chances are that if you deliver your parts blasted they will clean adn dip it. But, do not use anything that comes in a can.
When powdercoating galvanized parts the zinc phosphate is an absolute must.