Quote: I do use the dupont and ppg wash(acid) primers over freshly sand blasted metal, have been for a long time. It provides extra grip I believe if I'm going to all the trouble of sand blasting.
615s variprime is the dupont paint and PPG make 2 kinds and only one is OK for blasted metal, it works good as I have been painting trucks since the 90s and keep my trucks for years.
IMO there's nothing better than freshly blasted metal to paint, I have never used any thing under my acid wash primer and then epoxy on top of that. I never even touch the metal after blasting before wash primer. I usually blast it and paint it the same day.
the acid wash primer is ensuring a bond occurs on the fresh metal.it forms a tight bond to the surface by chemical bonding. I have always PREPSOL rinsed blasted metal and used an epoxy containing zinc chromate as the rust inhibiting primer. an epoxy utilizes a mechanical bonding process which is exactly what you have with a [profiled] blasted surface. the main difference between the two systems is the epoxy's zinc is in direct contact with the steel surface and ensures complete rust control. the acid primers tend to lean more towards the bonding process. if the metal is slick, the acids are much better at maintaining the bond. the acid primers are more tolerant to contaminants than the epoxy is. with the proper/ clean profile on the metal, an epoxy will perform very well also.
the acid wash primer is ensuring a bond occurs on the fresh metal.it forms a tight bond to the surface by chemical bonding. I have always PREPSOL rinsed blasted metal and used an epoxy containing zinc chromate as the rust inhibiting primer. an epoxy utilizes a mechanical bonding process which is exactly what you have with a [profiled] blasted surface. the main difference between the two systems is the epoxy's zinc is in direct contact with the steel surface and ensures complete rust control. the acid primers tend to lean more towards the bonding process. if the metal is slick, the acids are much better at maintaining the bond. the acid primers are more tolerant to contaminants than the epoxy is. with the proper/ clean profile on the metal, an epoxy will perform very well also. 
