protecting my bare shell

[NicolasW]

RickM et al. -
Just talked to the owner at American Stripping (my local industrial/military stripper and powdercoater....http://www.ascoweb.com). He gave some very useful information....which is as follows:

- Sandblasting may be able to take off undercoating if it is old and brittle. Chances are, if you can gouge it with your fingernail or screwdriver and the gouge stays, sandblasting will not be able to remove the undercoating. You also don't want to powdercoat with that undercoating on the car because the chassis has to sit in a 400 degree oven and it will drip off like molasses. If the undercoating is soft, you will need to remove it with hard labor scraping, heat guns, and chemicals.

- He cautioned that powdercoating is not the be all and end all...it will depend on the specific seam sealer and spot welds in the chassis. Since the chassis has to be in a 400 degree oven, it may affect the spot welds and loosen the seam sealer, possibly tweaking the alignment of the chassis.....usually determined on a case by case basis. If he looks at a car and determines that powdercoating is not the best idea, he suggests media blasting followed by conventional spray primer to protect the metal.

- While there is powder out there that may contain zinc, it is usually less than 50% which may not be enough to act as a galvanic couple and actually prevent corrosion in the body. What normally happens, is shops use a "zinc containing" powder, then coat with a powder top coat which essentially gives you two coats of powder which may not protect any more than two regular coats of powder.

- Overall cost estimate for sand blasting and powder coating the whole chassis inside and out (minus doors, roof, hood trunk and fenders) was in the range of $1200 to $1400.

Whew! I think I covered everything he said.....

[adomakin]

more info!, i love it!

[NicolasW]

adomakin -
I think the information that you're looking for is....do you need to put a coating on the metal after sandblasting but before final finishing?

When I visited ASCo, he had a 1940's chassis that had been sandblasted and the metal still had that bare matte grey look...no rust! The owner said that as long as you keep your greasy fingers including salt and acid off the car, the metal will do fine. He cautioned that if you're going to be working on the car, it should be covered with something to prevent oxygen from getting to the surface.

Your primer depends on whether you want to cover up the primer later or take it off again before final finishing....I don't really have an answer for you but I would suggest a quick primer spray after sand blasting to protect the metal....you may also want to check out the myriad of "projects" at http://www.gunnarracing.com which go through the process of getting to bare metal, priming, painting, etc.

[Grady Clay]

I have a like new ’74 914 body/chassis sitting in a trailer. It is still gun-metal gray with only a slight brown patina to the surface. I had it caustic stripped and then well washed in ’76 and have kept it all these years as a spare chassis for my original 914-6 CP/GT-2. As you can tell, I didn’t pay any attention to preserving it since it was just some replacement sheet metal. Living in Denver with thin air and little humidity the car is well preserved.

If I want to put this back in service as a hot-rod six, what is the best way to proceed? 911s have the same issues.

Best,
Grady

[pryord]

According to the research I've done, 2-part epoxy primers are the best choice if there will be a time lapse before painting. They are not as permeable as other primers. The Sherwin Williams website is a great resource and they will answer questions from newbies like us. I'd say email the professionals and do what they say.

David

[barlowdo]

Some questions I have pondered ?

1. Do late model sheet metal replacement parts already come galvanized so they are galvanized just like the later model cars were ?
2. If you use Epoxy primer do you have to be careful what compatible paint you put over it?
3. Is it true that once you acid dip, the car will keep rusting because you can never truly neutralise all the acid ?

[RickM]

I'll take a shot here:

1: The late model ('85) parts I've seen from the factory are galvanised and primed with a zinc based primer.
2: As mentioned by BG you should stick with same brand/same system materials.
3: The acid dip is used to remove the rust and then rinsed with water. I've never heard of a car continuing to rust when rinsed properly. That doesn't mean it can't happen. Others here can speak from exeriene.