Painting Evaporators

[vendo81d]

What is the best way to get a long lasting paint job on evaporators?  I have been having a big problem with my Vendo 56.  I removed all of the parts that I could and had them powder coated.  The remainder I sandblasted and cleaned with wax and silcone remover.  I then coated it with Seymour Cold Galvanizing Primer followed by Seymour Alumi-blast and Seymour Clear Coat.  I noticed today that the paint is flaking off.  The powder coating is doing fine, but I don't think I got more than six months out of the paint job.  I don't know what to do next.  I have done five evaporators this way and now I have to re-do all of them.  Any suggestions?  I have attached a picture of the problem.

[ss540]

I have never painted an evaporator on any of my resto's.  I just clean them as well as possible and straighten any bent fins.

[cohammer]

If you want to pant the metal, paint it and clean the copper and leave it raw. Just my thinking.