[Old Fool]

Originally Posted by John long

I have used DPLF for years and even though I have recently changed to SPI epoxy which I much prefer I do not think the PPG is a bad product. I am in the middle of repairing some bubbles in the crease of my 36 Ford roadster door that was painted 4 years ago. The door was stripped to bare metal, primed with DPLF, primed with K36, sealed with DPLF and painted with Concept? In order to determine why it failed I took a razor blade to it yesterday to determine at what level it failed.

I was amazed to find the bubbles go all the way to bare metal. All layers of paint have good adhesion. To my surprise the metal is perfectly clean and shiny.......Too shiny. THIS FAILURE IS MY FAULT. When I stripped this door I treated it with RustMort and wire brushed the crease area. There is no doubt The failure is the result of me failing to neutralize the acid and/or polishing the metal to the point the paint had no tooth to bond to. Add to this it was painted in a very cool shop.

The point I am trying to make is these modern materials work by chemical reactions and depend on the proper procedures being followed. That includes temperature, preparation, Mixing ratios etc, etc. Rarely is a failure due to the product being bad even though I wish I could blame it on the paint.

John H

Wire brushing burnishes the metal, it leaves no anchor pattern.

[Dayo5]

I really appreciate the replies!
Thank you

[deadbodyman]

Originally Posted by John long

I have used DPLF for years and even though I have recently changed to SPI epoxy which I much prefer I do not think the PPG is a bad product. I am in the middle of repairing some bubbles in the crease of my 36 Ford roadster door that was painted 4 years ago. The door was stripped to bare metal, primed with DPLF, primed with K36, sealed with DPLF and painted with Concept? In order to determine why it failed I took a razor blade to it yesterday to determine at what level it failed.

I was amazed to find the bubbles go all the way to bare metal. All layers of paint have good adhesion. To my surprise the metal is perfectly clean and shiny.......Too shiny. THIS FAILURE IS MY FAULT. When I stripped this door I treated it with RustMort and wire brushed the crease area. There is no doubt The failure is the result of me failing to neutralize the acid and/or polishing the metal to the point the paint had no tooth to bond to. Add to this it was painted in a very cool shop.

The point I am trying to make is these modern materials work by chemical reactions and depend on the proper procedures being followed. That includes temperature, preparation, Mixing ratios etc, etc. Rarely is a failure due to the product being bad even though I wish I could blame it on the paint.

John H

So the rest of the door didnt have any adheasion issues,it was just at the body line???

[John long]

Originally Posted by deadbodyman

So the rest of the door didnt have any adheasion issues,it was just at the body line???

It appears so Mike but I am not ready to answer for sure yet. I have blocked the door down with a long board and 180 grit and am going to feather it in about 3 inches from the body line. At that point I can tell if the DPLF is adhering out to where the 36 grit scratches are. If it is, I am going to prime it with SPI epoxy. If not, obviously I will have to go ahead and strip the whole door. The doors have been painted for at least 5 years and these bubbles along the crease line are the only failure anywhere including the jams. Ironically both doors have bubbles in exactly the same places.

So far, I am finding places in this groove I can peal the epoxy of with my pocket knife and areas that are adhered well. Even though I have no failures outside the groove I need to feather it down and check it.

I will post pictures and description of what I find.

John L

[John long]

Well, here we go. I have one door blocked ready for Epoxy. It appears to me the issue is only in the body reveal line. You can see that the DPLF feathered well once I got back from the reveal. It also has adhesion and can not be scraped easily with a razor blade. I found:

Very shiney metal in the groove

Lots of material build up.

Unable to determine if any acid residue.

I have scuffed the bare metal well with 180 grit dry and will clean it well with W & G remover letting it dry well before I prime with 2 wet coats of SPI black epoxy.

I am going to post a couple of pictures that I hope show what I have done.

[deadbodyman]

John, this raises a good point, I always say,if you use ospho or phosphric acid always sand it well before you prime.when I sand I always sand the field first and the edges and body lines last by hand sometimes I forget a body line so I always sand all the lines at the same time so I dont miss any and all the edges at the same time for the same reason ..It looks to me like you may have simply missed hand sanding the lines ,its an easy enough thing to do since the cant tell just by looking at it like you can with a primer and thats why SPI says they dont "recomend" using acid products ,it's so easy to miss something even for a pro but theres so many ways a newbie can screw up using acid its just easier to completly eliminate them from the equation...Sure the job wont last a long without uing acid but it'll look good for as long as it does and without any issues

[John long]

I will also clean it good with W & G remover before I prime it. Thanks for the interest and advice.

John L