crashtech
Combo Man & Mod
I'm looking to have a discussion about procedures and results when applying poly primer over epoxy in cool temperatures, meaning metal temps around mid-sixties.
I've encountered issues involving too fast of application, and have been in the process of refining the technique to avoid problems.
But I had a problem just lately that will probably result in the stripping and redo of two doors for a '70 GTO, because the epoxy never hardened.
The doors in question had been stripped and epoxied the week previous, and had some filler and some bare metal spots.
The technique used was to apply two medium wet coats of unreduced epoxy on a Friday evening, about 20 minutes apart. Closer together than normal, but I have done this before when the parts will sit awhile with no ill effects. The hardener was the bottom of a gallon that had been in use for a little over a month. I remember clearly mixing it, because it was unusual that the amount of hardener in the can matched almost exactly what I needed in the cup.
Heat was left on during the weekend to provide about 65° metal temp.
Sunday afternoon, about 44 hours later, I came in just to spray 2 coats of G2 polyester primer. This seemed to go fine, with about 10 minute flash time.
Tuesday, about 48 hours later, I began to block the G2 with 100 grit and noticed the epoxy pulling off the metal. After a call to Barry, I put the doors out in the sun during business hours for 2 days. They were exceeding 100° metal temps doing this.
Then I left them alone for 2 weeks. Today, coming back around to block them, I can still see the epoxy pulling off the bare steel, and it can be marred with a fingernail. I'm fairly convinced that it all has to come off now.
I'm curious to know if anyone has experienced anything like this, and what was done to resolve the problem. PM me if you don't want it to be public.
I've encountered issues involving too fast of application, and have been in the process of refining the technique to avoid problems.
But I had a problem just lately that will probably result in the stripping and redo of two doors for a '70 GTO, because the epoxy never hardened.
The doors in question had been stripped and epoxied the week previous, and had some filler and some bare metal spots.
The technique used was to apply two medium wet coats of unreduced epoxy on a Friday evening, about 20 minutes apart. Closer together than normal, but I have done this before when the parts will sit awhile with no ill effects. The hardener was the bottom of a gallon that had been in use for a little over a month. I remember clearly mixing it, because it was unusual that the amount of hardener in the can matched almost exactly what I needed in the cup.
Heat was left on during the weekend to provide about 65° metal temp.
Sunday afternoon, about 44 hours later, I came in just to spray 2 coats of G2 polyester primer. This seemed to go fine, with about 10 minute flash time.
Tuesday, about 48 hours later, I began to block the G2 with 100 grit and noticed the epoxy pulling off the metal. After a call to Barry, I put the doors out in the sun during business hours for 2 days. They were exceeding 100° metal temps doing this.
Then I left them alone for 2 weeks. Today, coming back around to block them, I can still see the epoxy pulling off the bare steel, and it can be marred with a fingernail. I'm fairly convinced that it all has to come off now.
I'm curious to know if anyone has experienced anything like this, and what was done to resolve the problem. PM me if you don't want it to be public.
