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

[Dave Bell]

I have used POR-15 on 3 914's. I have only used it after stripping completly down to metal. Only used it in areas that are not visual, e.g. front and rear trunk, engine compartment, floors, longs, windshield channel,weather stripping channels, light buckets etc.... Stuff has worked great.

On the engine compartment and some other places, I used the POR-15 tie-coat primer on top of POR-15 so I could more easily paint another color, or the car color/paint itself on top. This also seemed to work well.

On the underside of the car, I can't imagine trying to strip all of that tar based stuff off myself... maybe media blasting by some outfit... and after that I would not put on POR-15... I would probably primer and paint to the body color or just black if I went that far.

To repair smaller spots on the underside of the car, I stripped the spots and coated with some Henry's roofing compound, which seemed to match the consistency and look of the stuff the factory put on... and it was cheap, it stuck and is it is waterproof! Probably burns like the factory stuff too... every light some of that factory coating off while welding... I have.

- Dave