Blasting, welding, priming suggestions

[BigFlo]

I am planning to send my body out for media blasting. The passenger floor and trunk floors will be out and will be replaced after blasting. Other panels sections will be replaced like lower quarters.
The guy who is blasting it, can also prime it. He can use either etch or epoxy.
Based on what I've read, (mostly on this forum) I want to put an epoxy primer over the bare metal, after blasting. The guy who is media blasting suggested to use an etch primer because it will be easier to remove on the areas that need to be welded.
I don't know enough about paints/primers to know if that is going to be an issue. Is epoxy going to be very difficult to remove prior to welding? Is it going to make that much of a difference vs removing etch primer?

If I go with etch, I would need to cover it with an epoxy later anyway, to get a good primed surface correct?

 

[kev]

Go with epoxy. No regrets with epoxy.

 

[Donny]

I use 'em both, first etch on bare metal, do the metal work on etch, keep it out of the weather...after metal work, put it in epoxy.

 

[66_B_Body4ever]

Like Donny said, etch is never a bad idea before epoxy. Some epoxies, like black and white, require an etch coat prior to epoxy application. Etch itself, will allow rust to form through the primer, which is not a desirable thing. Etch is designed to promote a chemical adhesion to steel so that primers, surfacers or topcoats will adhere to the substrate.

Epoxy is best... grind away what you have to, and later on, all you have to do before filler is sand the cured epoxy with 80-100 grit before applying body filler.

 

[Cranky]

Etching primer is what you're talking about?

 

[snakeoil24]

Blast, dry vacuum, blow out with dry air and vacuum 5 times more. Then apply a phosphoric acid with Zinc. This will give you a few weeks before rust starts. Clean and wipe down body with wax and grease remover. Light sand surface with 180 then clean again and wipe down with wax and grease remover. Do not let your friends touch the body. Finally apply 2 coats epoxy. then dust entire body with 3m guide coat powder and block entire body. Look for all your issues

 

[Photon440]

snakeoil24, what is this 'sanding powder' you speak of? I'm not familiar with it. I searched, and didn't find anything. Thanks...

-=Photon440=-

 

[BigFlo]

Thanks for all the input. Like most of us, I don't have tons of time to dedicate to the project - so based on the amount of time it may take to do the bodywork after it's blasted, I should probably get epoxy on it as soon as possible. Then I won't need to worry about rust creeping back.

 

[BigFlo]

I just saw this product today for the first time. Snakeoil24 can correct me, but I think he is referring to a dry guidecoat. It's a dust you apply to the surface that acts like a paint guidecoat to help identify low/high spots. I saw a product called 'Farecla Dry Guide Coat' on Eastwood's website and 3M must also make it.

 

[snakeoil24]

yes dry guide coat

 

[Photon440]

Guide coat. Okay, that makes sense. Thanks for the answer.

Does it apply as a powder with a brush, or get blown on? What are it's advantages over an aerosol guide coat?

-=Photon440=-

 

[66_B_Body4ever]

Of note, and perhaps it's a misprint, but epoxy is not intended as a 'sandable' primer. Use primer surfacer for that purpose. The epoxy is a sealer/adhesion promoter for subsequent coats of surfacer etc... It does need to be sanded before surfacer is applied (once cured), and a guide coat helps you identify where you have/haven't sanded, but don't bother block sanding epoxy, that's not its intended purpose.

 

[66_B_Body4ever]

Guide coat. Okay, that makes sense. Thanks for the answer.

Does it apply as a powder with a brush, or get blown on? What are it's advantages over an aerosol guide coat?

-=Photon440=-

If you've never used it before, click on the link for a shameless promotional video, that will give you an idea... for what we're doing, avoid the use of machine sanding btw...

http://www.youtube.com/watch?v=c3B4VWA4cE4

 

[snakeoil24]

Yes apply guide coat which is a powder directly to Epoxy and lightly sand with a board. All dark spots need filler and opposite will need metal work. You still can sand epoxy even tho its not meant to be. just remember filler over epoxy never under. then your going to appy more guide coat and finally re spray with epoxy then multiple layers of sandy clay followed by a ton more blocking. Then you will use 2 k over the sandy.

The bug advantage of 3m dusting it does not clog the paper.

 

[Jerley87]

Etch primer over bare/blasted metal...Always!

 

[Beekeeper]

I also vote etch primer then metal work then epoxy sealer then high build
Primer,guide coat then block sand

 

[snakeoil24]

Etch primer is nice but not compatible for a long period with Epoxy. Look at the web sites for all the Paint MFG they tell you that.

 

[Donny]

I've never heard of etch not being compatible with epoxy, humm, I'm interested in validating this claim! How I use etch, of course on bare metal after being media blasted, the etch primer dries to a consistency of sandpaper, which I sand down, and, you can see the penetration of the etch green primer into the metal, this is crucial as this deposits the chemicals that hinder rust growth-I want to say rich in Zinc, but, I'm not sure. I do know that it works -- works well I might ad.

 

[snakeoil24]

Donny that is a Zinc rich prep

 

[Donny]

Some say that its over-kill to do self etch then epoxy, it might be, but, I'd rather be safe than sorry, perhaps this extra step will be the undoing of this process...I did put some epoxy down on some bare metal yesterday, it layed down nicely and dried nice too. The main reason I use zinc rich self etch is the media blasting process removes some of the factory zinc coatings. Sand blasting removes it ALL.