Painting the trunks/engine bay/underside/cabin, POR-15 and leave black? Options

[boxsterfan]

I have been thinking about what I will do with my car in the future when it comes time to restore. On many cars, I see people have appeared to POR-15 (or other) the trunks/engine bay/underside/cabin and then left it black? They then go on to paint the rest of the car as normal (orange, red, white, green, etc...)

I'm not looking to build a concourse winner myself. I am looking to build a car that is restored and protected from rust for as long as possible (another 40 years lets say).

What do people think of POR-15'ing (or any other product) the trunks/engine bay/underside/cabin and then leaving those areas as that? And then (in my case blue) painting the rest of the car as normal?

[shoguneagle]

I have used the entire Por-15 system inside the car and underneath. I treated the surfaces inside the uni-body and everything else with phosphoric acid (10-15% solution; aka metal etch) which converts the rust to an oxide; where I could, wire brushed and sanded treating the areas a couple of times so any rust is inserted and could not flake. Follow the instructions completely and carefully especially when you are going to paint over it. Por-15 is NOT photovoltaic friendly. You do need to use paint in areas where sunlight can get to it. Underneath the car you may not have to since it is almost always not exposed to sun rays. The same may be said for the cockpit area and the trunks; if in doubt, use paint over the Por-15.

Por-15 housekeeping is a different story which means keep everything as clean as possible; wear gloves, mask, old clothing, etc. It seems to get over everything including including the personal items. If split, clean up immediately since once it drys it develops a hard coat. Just take your time and do not get in a hurry.

IF I WERE to do it again, I would wire brush/sand areas down where I could and flush inside the unibody where I could to eliminate as much collected rust and convert it to metal oxide. I would flush and treat several times to ensure any possible rust areas are covered.

For the areas that can be painted get a good primer sealer and paint over it once applied. The trick to reoccurring rust is not just covering it with such items as Por-15, but is to first get areas converted to metal oxide and then seal,paint,etc. You do not want to have any rust to be in a flaking state.

As far as the insides of the unibody, there are holes you can go through to put phosphoric acid solution through, wash out with water (several times on each of the foregoing), and then put prevention through them. Years ago I got this information from Sir Andy but unfortunately it was stolen from me via Barstow. It is somewhere in the threads.

The system I would use is the wax one which I believe comes from Europe and was the method used for years to get preventative chemicals inside the unibody/frame areas. You pump warm/hot wax as the carrier into all the enclosed areas with the idea it will carry the needed chemicals to all the areas needing treatment. You would have to do another search to find out how it is done and where to possibly get it.

Take your time and have fun.

Steve