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?

[McMark]

If you really want to do it, strip it to metal, epoxy primer, real catalyzed paint, then undercoating. None of these things come in a rattle can, and most require specialized equipment to apply.

However a scrub down with a wire brush to remove loose material and a new application of undercoating should be sufficient. Pressure washing with solvent to get rid of oil/grease would be prudent as well.

I think the bottom line for me, is that there is no magic potion - no perfect cure. Everything has a up and a down side and the best way to prevent future rust is to limit exposure to water, and more importantly eliminate areas where water can sit trapped. It's not splashing through a puddle that rusts our cars. It's the pile of dirt behind the rocker that soaks up water and holds it against the metal. It's the loose undercoating/seamsealer that allows water to wick in behind them where that moisture will sit for a long time eating at the metal. Remove those hiding places, and limit exposure and the car won't rust appreciably for your lifetime.