Rust

[chris.richard]

My powdercoating is stripping off in sheets because the chassis is rusting under it, perhaps because the car lived under a tarpaulin for years. Is this a common problem? How do people protect the chassis from the elements?
I'm busy with wire brushes and angle grinder, then I intend to use satin finish Hammerite. Hadn't planned on this task - I suppose there will be lots more unplanned activities in the future.

Hey Ho

[CorseChris]

Chris,

After my experiences of powder coating on other cars, I wouldn't use it again. If you can, galvanise and paint, if you can't galvanise, grit blast followed by an etch primer followed by a 2-pack colour finish is almost as good and at least allows you to make localised repairs or mods without too many complications.

[mogul_x]

Chris,

Since the surface is already rusted, I'd recommend a product called POR-15. I'm not sure how available it is in the UK, but it's a pretty common item used in auto restoration 'Stateside.

"POR" stands for "paint over rust". It's a chemical that will react with the iron oxide (rust), converting it into a rust inhibiting primer. Pretty easy to use - just scrape off loose paint and scale, apply, and once it's dry, you're ready for additional priming or painting.

After that, any epoxy based primer or topcoat should give ample protection, as Chris S. already indicated. That's about what was done to my Nova, except that after the epoxy primer, I used a urethane based color coat.

[chris.richard]

Thanks, Scott

POR15 is available over here, fairly expensive, but it seems good. It's about a 3 or 4 part process, isn't it?

I decided not to go that far, as the bits of the chassis under the Glassfibre are what'll kill the chassis eventually, since I can't get at them. Some of the worst bits seem to be the sills. Anybody ever taken the tub off? Hence I'm only derusting and Hammeriting for cosmetic rather than longevity reasons.

[mogul_x]

Chris,

POR15 is a little pricey, I'll admit. I'm not sure about the number of process steps. I know they have several different compounds, which can be used in conjunction, but I'm not sure if they must.

As for the removing the tub - It doesn't look all that difficult on an unfinished kit like mine, but I'd bet that it could turn into a handful on a completed car. There's a lot of adhesives used on the hinge post and front bulkhead, and this will be a real pain to get undone if the adhesives are still doing their job.

Of course, if the powder coat is coming off as badly as you say, the adhesive joints may not have a lot of integrity left. It could come apart very easily once you drill out all of the rivets.

On my car, I was planning on caulking all of the joints between the frame and the tub, painting the entire assembly (top, bottom, inside and out), then layering on a gererous amount of rubber undercoat in an attempt to keep moisture out. It may not prevent corrosion in the long run, but it might slow it down.

[chris.richard]

Originally posted by mogul_x
On my car, I was planning on caulking all of the joints between the frame and the tub, painting the entire assembly (top, bottom, inside and out), then layering on a gererous amount of rubber undercoat in an attempt to keep moisture out.

That is one BIG task!