KTM520guy said:
You should not have any peelage problems if you sand correctly.
"The Big D" is not rural. No soup for you!
That sounds like a good theory, but my experience has shown otherwise.
I used DP40 almost exclusively as a primer sealer in my collision repair shop for well over a dozen years because it was better than anything else I could find (I warranteed my paint work for as long as the customer owned his/her car so I had to be serious about the materials and processes I used).
But I got bit more than once by my painter not reshooting DP as a sealer when he came back over a sanded DP application and just painted if the car sat too long.
The typical scenario was for a car to be primed with DP and then sit a few days while we continued to prep other cars (in a production shop, you have to always keep working, and sometimes, a job was delayed waiting for parts).
By the time the final sanding and prep was done, it could be a week or so before we were ready to paint, but my painter would think it was OK to go right into color because, technically, he was still within the cure time. However, hot summer days in Houston shortens up the time that DP will case harden.
To make the long story short, I had to redo a couple of these cars, and it was amazing to see an area where the paint had peeled off, leaving that really purty look of nicely sanded DP underneath.
Paint adheres by both mechanical adhesion AND chemical adhesion, and while you "might" get lucky with just sanding DP and going to color beyond it's cure time, I'll take chemical adhesion over mechanical adhesion any day if I want a truly long term finish.
Even when you get lucky and the paint doesn't peel off in chunks, you'll still see that a finish applied without repriming beyond the "open time" of the DP will chip much easier when hit with gravel or whatever.
You have to understand that conventional (non-curing) primers stay open indefinitely which results in two features:
1. Since a non-curing primer stays open indefinitely, all you have to do is sand before painting because that primer will allow the topcoats to bond with it by "soaking in".
2. A curing primer like DPLF goes "closed" after about a week so even if sanded, the topcoat can't penetrate it for the kind of improved bond you can get with a sanded conventional primer.
Even then, the chemical bond between a topcoat and fresh DP has much more integrety than the bond between a sanded conventional primer and the paint on top of it.
It's also been said that any primer MUST be topcoated to achieve full protection of the base material. That's true, however, DPLF isn't just "any" primer. Yes it does stay chemically open for about 7 days (that's pushing it) and during that time it can be contaminated because it isn't yet a chemical barrier, but after that, it does serve as a good protectant all by itself.
Yes, it is designed to be topcoated for full intended protection, but it's better than just any primer without a topcoat. For typical inside applications, it's really more than you need.
Conventional, non-curing, primers are terrible protectants by themselves because they never "close" and are not at all a good barrier against moisture and other contaminants which is why they must be topcoated.
And since your info says just "Texas", I had to assume you were in the middle of nowhere and in a town nobody would recognize.
Unless, of coarse, you're embarrased to live in Dallas and don't want anyone to know?...
I still want my soup.
