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Discussion Starter · #1 ·
as I'm working on the firewall I noticed this surface rust. Is there something I can spray on this to stop the rust? What do I clean and prep the firewall with before painting it? I am going to use rattle can to paint it. I purchased some Easton etcher primer, will this stop the rust?
 

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That looks like flash rust from being exposed too long? Knock that stuff off again, clean it with acetone or lacquer thinner and prime with epoxy primer. You can buy epoxy in a rattle can. I think that’s the best protection you can get. Self etch is a can of worms because it does not protect from moisture and has several compatibility issues.
 

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Kimmer has it right. Sand or sand blast it clean and then clean with wax and grease remover or lacquer thinner. I'd then use compressed air to make sure there are no fibers from the rag you used to clean it. I like the green self etching epoxy primer you can get at any auto parts store or hardware store in a rattle can. You can get self etching epoxy primer from any good jobber paint store as well, if you want to spray it with a spray gun.
 

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Jasco metal etch/prep is a phosphoric acid that is used to stop rust. I have used other products that are similar to this but they have not been available.

If your climate is humid you might need to use a rust inhibitor like the Jasco product I mentioned above.

I clean my parts with lacquer thinner prior to priming.

You’ll probably want to seam seal the joints of metal panels on the firewall before you get it all painted.

I have used Rustoleum self etching primer and satin black on all of my chassis, firewall, undercarriage, wheels for the last 10+ years..

This is the firewall of my 63. I treated it as described above and continued the process all the way back to the tail panel..
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Discussion Starter · #6 ·
thank you for all the info. First timer here doing any of this. Do I need to seal the seams prior to priming? Is there somewhere I can go to get a picture or diagram of all the spots that need to be sealed. I still need to work on the floorpan that was replaced so I'm only to go down to the weld line right now.
 

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I followed the perimeter of the main center panel of the firewall. There are joints at the top and down both sides. Looks like the passenger side has been worked on a bit but the joints on the driver’s side are all clearly visible.
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thank you for all the info. First timer here doing any of this. Do I need to seal the seams prior to priming? Is there somewhere I can go to get a picture or diagram of all the spots that need to be sealed. I still need to work on the floorpan that was replaced so I'm only to go down to the weld line right now.
this Is where the compatibility issues come into play. Some seam sealers are ok on bare metal, some are not. Most are ok on top of epoxy primer. Most are not ok on self etch primer. 3M makes good quality seam sealers and I’ve had great luck with them. They are a bit expensive. The product data sheets are helpful for determining which substrate is acceptable. I think the 2 component (2k) sealers, are ok on clean, bare metal. They require a special applicator gun. The 1k urethane based sealers are not recommended on bare metal or self etch primer, to my knowledge. It gets to be a confusing puzzle fast which is why epoxy primer, even though it’s more work/$ to achieve, is at least easy once it’s down. You can put any seam sealer you want on it followed by any top coat you want. Like @Nova Thug mentioned, the phosphoric acid treatment is really good. You can leave the metal bare for a very long time with no rust. I used that stuff on my roof panel and left it for months (in my garage) with zero rust.

these are just my thoughts based on my experiences. Im definitely not a pro.
 

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I know I used a 3M seam sealer at the time I did my firewall area. I don’t remember the exact formula I bought at the time but I kept the tube so I could get more of it when I needed some. The stuff I used doesn’t have a long shelf life once you open it you better use it or if will set up and be useless. Figure out as many seams as you can to use up the tube. This was a standard calking gun tube. The firewall won’t need that much by itself. I did my drip rail channels and rocker to quarter panel and qp to C pillar joints. Also, the joints in the door jams and the center panel between the rear window and deck lid. There are other places it can be used but you will need them to be ready for the sealer.
 

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Here is the "epoxy" 2-component seam sealer. https://www.3m.com/3M/en_US/p/d/b40066526/ The urethane single component stuff :https://www.3m.com/3M/en_US/p/dc/v000232289/. I have read that the "fast & firm" stuff is good but I've never used it. https://www.3m.com/3M/en_US/p/d/b40069454/. I have used the Barrier Bond brush on stuff inside my quarter panel repair seams with decent results. This stuff is a little more difficult to work. https://tcpglobal.com/collections/brand-barrier-bond/products/brb-ss101-qt.

Eastwood and Amazon have rattle can 2k epoxy primer. Quite expensive at $30/can but good stuff. Just be sure to plan your work well to maximize usage/minimize waste. Once you activate a can, its done once the clock expires. I think you get a couple of hours pot life. https://www.eastwood.com/eastwood-s...ickedid=602838622301&wickedsource=google&wv=4, https://www.amazon.com/SprayMax-Act...t=&hvlocphy=1025649&hvtargid=pla-569092577986

All that said, you can use self etch primer followed by a top coat of regular primer or even paint, such as rustoleum, then seam seal and top coat again. You can achieve excellent results this way, just be aware that it's not as durable as the automotive, catalyzed stuff. I used a lot of rustoleum paint and self etch primer on my project. I applied it all with an HVLP gun plus mixed it with hardener from tractor supply. The insides of my quarters and interior metal were all done that way.

Best of luck with your project. Hope at least some of this is helpful.
 

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It is not a good practice to use lacquer thinner as a final clean. If you understood the theory behind final clean, you would understand that lacquer thinner has too fast of flash time. Use a quality wax and grease remover with the proper technique.
You are severely limited when only using spray bombs. The products are compromises at best so be sure every step is perfect. Tech sheets need to be read for every product. Reading on the internet to use phosphates or metal conversions is not a good idea. Some products specifically state not to do this. Info is limited for spray bomb products vs. professional products so again there are compromises with spray bombs. .
Etch primer is a great product when used properly, there is no such thing as etching epoxy, at least from reputable companies. Epoxy is also a great product (never use both) that performs similar functions to etch but with different uses. I have been using etch and epoxy for almost 40 years, I still choose one or the other based on the job at hand. Neither is the answer for everything.
Seam sealer needs to be selected based on the application. 2K is best but I would not have an issue with a 1K on the firewall. Again, read the tech sheet to see what substrate the sealer can be applied to and the cure/dry times. An acid brush with shortened bristles will give you the factory brush strokes in your sealer.
For a properly prepared bare metal firewall, I would probably use a low gloss black epoxy, then watching cure and recoat times, apply proper seam sealer, then follow with more epoxy and leave it or topcoat with color of choice. I would have to read up on the sealer used, you might be able to topcoat color directly over the seam sealer but I am guessing it would be best to apply epoxy or primer-sealer over the seam sealer.
 
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