[larrynew]

Anyone have any experience spraying Sherwin Williams P60g2 wash primer over NAPA 7220 self-etching primer? Searched the archives and couldn't find that specific question. I'm close to spraying the P60g2 on some exterior parts and need to know if I need to strip the 7220. In addition to all the mating surfaces, I used 7220 on other places early in the build like the rear spars on the vertical and horizontal stabs.

 

[larrynew]

Hopefully, the results of my test will be helpful to someone with the same question. I applied Sherwin Williams G60p2 Wash Primer over a test piece and let it dry for 24 hours. The test piece had three sections, bare aluminum, bare but scotchbrite scuffed and NAPA 7220.

My unscientific method to check adhesion and compatibility was to scratch and attempt to chip all the sections equally with increasing pressure from several sharp items and then to hand rub with a maroon scotchbrite pad. I also tested a section of plain NAPA 7220 to a section of SW G60p2 over NAPA 7220 with a scotchbrite rub.

My conclusion: Sherwin Williams G60p2 was equally tough and durable over all the surfaces and was significantly tougher than the plain NAPA 7220 when scotchbrited. I couldn't find any adhesion problems with G60p2 over 7220. The picture below is pre-scratch and scuff.