Sherwin Williams GBP 988 Self Etching Primer is one of the best,it actually bites into metal or any surface,prepped or not,it's not a heavy build primer,so it's perfect for keeping the metal from flash rusting and when you have to go back into it for any reason,welding,body work,it won't give you hard time, I've been using this stuff for a while and love it, I think I pay around $8 per can