Problem with primer lift?

[trent]

As I was block sanding today, I noticed that in almost ALL of the sharp 45deg indent corners, the primer had lifted. I am not entirely sure how this happened. When pushed down, it cracked right in the center. I am using a PPG 2K primer over MP170 epoxy. LAst weekend, I sprayed the MP170 epoxy primer, and the very next day the high build. The car sat for a week before I had time to start sanding. I did not sand or scuff the MP170 since I was within the window. Did I just build too high in those corners? I sanded them and feathered them down to metal, and I have to reshoot, but do not want to happen again. :(

[Phil V]

Trent, critical question --- the primer that lifted, did it lift from the bare metal or did the 2-K separate from the epoxy primer ? I think I already know the answer but it has to be asked anyway.

[trent]

Trent, critical question --- the primer that lifted, did it lift from the bare metal or did the 2-K separate from the epoxy primer ? I think I already know the answer but it has to be asked anyway.

The high build lifted from the epoxy. The epoxy was still attached to the metal. :confused:

[Phil V]

Trent, I figured that was the case but I had to ask the question to make sure. It sounds to me like the basis of your lifting problem was not so much an actual lifting problem as it was that the 2-K primer was sprayed on too dry and it never adhered properly to the epoxy primer. Sounds like your air pressure was too high and you paint volume too low and possibly holding the gun too far away from the panel while priming. Does that scenario sound reasonable ? The bottom line is you have to spray that 2-K primer on wet so that it flows out a little. A little orange peel is normal but the primer should not go on dry.

[trent]

Trent, I figured that was the case but I had to ask the question to make sure. It sounds to me like the basis of your lifting problem was not so much an actual lifting problem as it was that the 2-K primer was sprayed on too dry and it never adhered properly to the epoxy primer. Sounds like your air pressure was too high and you paint volume too low and possibly holding the gun too far away from the panel while priming. Does that scenario sound reasonable ? The bottom line is you have to spray that 2-K primer on wet so that it flows out a little. A little orange peel is normal but the primer should not go on dry.

The primer went on VERY dry. I noticed that it was almost dry before it hit the surface (it would makes hundreds of little "balls" etc). I couldn't think of a way to make it more "wet." I was in fact outside in the driveway with the wind blowing, probably too high of pressure and my primer gun only has 1.4mm tip. I think I just had 3 strikes. :(

Most of the 2k is sanded down, so I will reshoot it wetter :)