POR15 over existing paint, ever done it? Options

[Doug Leggins]

I have been planning to use POR15 on the entire underside of my car. That is up unitl about 2 days ago. About a month ago we painted a couple of small areas on the tub. One area over bare metal and one area over existing paint. The existing paint area was scuffed, marine cleaned and metal ready was applied and then the POR15. I decided to strip part of the POR in the 2 areas just to see how well it had adhered. The POR over the bare metal had good adhesion. The POR over the prepped paint did not. Once I started stripping the POR it started peeling off in strips 1/2" - 2" long. Wasn't expecting that!!!

I had called the POR 15 place about 2 months ago and spoke to them about painting the POR15 over existing paint/undercoating. Got a standard line of its designed to be most effective on bare properly prepped metal. They said it may adhere well to paint/undercoating, it may not.

My experience so far is that it does not stick to the existing paint on the bottom of the tub.

Has anyone else used POR15 over existing original paint on there 914 with success?

I am currently looking at using a Sherwin Williams Epoxy Primer on the tub instead of the POR15. This was a recommendation from a local restoration shop that has used this product successfully on several cars. Anyone in this group used an Epoxy Primer?

TIA

[SirAndy]

Andy - Did you strip the paint off all surfaces before applying the por15? Or, did you leave some paint and put the por15 over it?

nope, only removed paint where i had surface rust. cleaned it off with brake cleaner which roughs up the surface, then applied Metal Ready (mostly around the rusted areas), then washed that off, then painted POR-15 ...

Andy