Painting Urethane over Lacquer primer

[htorod47]

I just finished the body work on my 46 Hudson Pickup truck.

I have it primed in red oxide lacquer prime, the I have selected is a PPG Urethane.

Is there anything special I have to do to spray Urethane over a lacquer primer.

Thanks

Randy

[rw7810]

Contact the PPG Tech support line... I'm sure they can tell you. Personally I would have used an epoxy primer.

ppgrefinishme@ppg.com

[htorod47]

Bob thanks for the reply and URL. I'll send them a message.

Randy

[GaryR]

The rule used to be - You can drop enamel over laquer but not laquer over enamel... not sure if that still hold true but I agree with rw, I would have sealed it off with epoxy to be safe..

[Vmarch]

Don't put polyurethane over lacquer primer, there will be inadequate bond. You need to seal the lacquer primer with an epoxy primer best if made by the same maker as the topcoat. Without the epoxy primer, it will chip with your fingernail.

[962porsche]

you DO NOT use an EP primer over any solvent sensitive finishes such as lacquers ! i was a BASF ( glasurit , RM , LIMCO ) paint tech rep. for years . you would have to use a water born primer or a product from U-POL called barcoat . SO YES it can be doen . but the best way is to remove the lacquer primer . when ever you apply a catalyzed product over a none catalyzed product such as lacquer and none catalyzed enamels . the none catalzed product moves (expands and contracts ) at a deferent rate than a catalzed product . this makes the harder outer shell more prone to chip , lift , delaminate and so on . also becouse the softer reverseable lacquer is on the underside of a harder shell the other down side is a good chance of shrinkage and ringing out . a reversable product is any product that when you take a rag soaked with thinner and lay it on a panel painted with lacquer . it will reverse back to its state when it was applyed .

[rnln]

962porsche,
wow. Since you mentioned about shrinkage. Can I ask about my past experiences? I painted parts many times, and the whole car once, with 3 stages paint (primer, color, and clear. Then sand buff). There were times it came out perfect, but there were times I had problems such as color coat melted when I spray clear coat. And times the whole things became wrinkle.

These problems I encountered when I bought spray cans at autozone or pepboys. When I bought paint at the paint shop to paint the whole car, I didn't have this problem. I asked the person at the paint shop, he said if I buy color and clear with the same brand, I should not have this problem, but I did. Also, there are times it came out perfect with the spray can, but it won't last long. After were times it last as short as over a year and the clear coat start to fade, oxidized, crack/pilled. Do you know why?

[962porsche]

except the base coat you should use all catalyzed products . and try to use only products from one paint system . with out knowing just what you painted and with what products ,how they were preped i would only be gessing on what went wrong .