Ecoat is electro coat primer that has been applied using electricity. The part is hooked up to a positive charge the primer is hooked to negative. The differnet charged primer is then sprayed onto the part. The reason they do that is so the ENTIRE part is covered with primer.
All major car maunfactors apply this type of primer for their factory warrantary to fight agaisnt rust.
I see that you are from MI and my guess is that you had those parts dipped at Ecoats?? right. Ecoat just like any other primer is not meant to be used as a stand alone product, it needs to be painted or the elements can break it down. You will need to scuff up the ecoat with something like a red scrothbrite pad then apply your regular primer. On the rad support I would just scuff it then apply some expoy primer then topcaot that with SS urethane black. On the hood scuff it and then apply your primer surfacer, block sand then more primer surfacer. On the underside wiat til you are ready to paint, scuff it seal it and paint it