Sealing Floorpan after Sandblasting - What Primer?

[JMarsa]

I'm going to have the rear wheel wells and trunk area of my Nova sandblasted soon in preparation for a min-tub. Afterwards I'll obviously need to primer the area to prevent rust. Is it better to use a etch primer or regular primer when there is welding yet to be done in the wheelhouse area? I'm concerned about 1st preventing rust until the work is complete and 2nd making sure the welds are clean (free of contamination). I've never had to sand etching primer so I don't know how tough it is compare to regular primer when prepping the areas to be welded.

Another question, does it make sense to etch prime the underside and then use POR (or similar) or another combination? I'm not planning on painting the underside, just a rust proof flat black.

Thanks in advance,


--JMarsa

[studehdtp53]

You don't need an etch primer if you are sandblasting. The surface is already etched. Any epoxy primer will do. I just bought some from Midwest Chemicals www.midwestchemicals.com that is the same formulation used on some aircraft. The bonding properties are supposed to be better than regular automotive primers and the cost was less even with shipping. I could not tell any difference in spraying it vs PPG DP 40 which I usually use. Just remember, primer stopping rust is only temporary, you will have to topcoat with paint depending on the climate the car is in on how long you can go without topcoating.

[JMarsa]

studehdtp53, thanks for the reply.

Expoxy primer is the yellowish kind right? I think it also has a high build too. Is it hard and durable like a two part expoxy used in fiberglass? How does it sand?

Thanks,

--JMarsa

[68protouring454]

not only does etching primer etch the metal but it gives it anti corrosive properties also, if you are going to finish paint the underneath right off i would etch prime, then urethane primer (high build) block sand then paint, but being undderneath of car depending on how far you are going with it, i would seal and paint it or if going show with it, i would urethane prime it.
etching primer cannot be bodyworked over, do all body work then etch prime bare metal, and go from there, goodluck
jake

[JMarsa]

OK I think I got the finishing process down.

Since I'm initially concerned about the 2 month period from when the floor is blasted and the metal work is complete and not making welding a pain for the body guys what brand/prouduct names should I use after the blasting to prevent corrosion?

Thanks,

--JMarsa

[parsonsj]

Jmarsa,

I'd shoot it with 3M weld through primer. Then your body guys won't even have to sand the primer to do metal working.

jp

[JMarsa]

I think I found it. Thanks for the tip John. OK now that I found this. Is there any limitations to what other types of primer I can spray on top of it? A preferred layering of products?

Thanks,

--JMarsa

[68protouring454]

weld thru primer is basically an etching primer, standox's etch primer can be used as a weld thru primer, and it does not seal out moisture, you can do this but, i would have it in a garage, where moisture will not get to it,otherwise it will start to flash rust, however i would wait till metal work was to be done, then blast do metal work and prep and paint, anything you do to it to seal it from moisture will just be a paint in the azz to the fabricator. i would epoxy prime it to seal it up, they should be able to grind where needed to do welding
jake

[gtome]

I just use DP from PPG and epoxy it, seems to work fine.

[redss86]

03-10-2005 10:13 AM
parsonsj Jmarsa,

I'd shoot it with 3M weld through primer. Then your body guys won't even have to sand the primer to do metal working.

jp

The 3M weld through primer is great for priming the surfaces to be welded together. 3M says to remove the primer from surfaces that have other work to be done to them, such as body/ paint work. I would recommend just using a good epoxy primer such as PPG's DP 90.

Good luck, jmarti81