What to do before Epoxy Primer to deal with all rust

[Rodney Nelson]

I was hoping someone could help to detail what needs to be done before Epoxy primer. Mainly to deal with the not so perfectly cleaned locations, the areas that it is hard to get to.

First picture where I am with my project. I'm trying to get the trunk area ready for Epoxy primer. I am replacing the pan and patching rust holes and some gas tank supports etc. I'm finding areas that it is impossible to get too. I have also had my entire '72 911 chemically dipped. I can see surface rust and gunk it is impossible to get to inside some of the cavities, areas where there are seam filler looking materials where I just can't get it clean enough.

So with the above said what materials and steps should be taken.

For example, rust encapsulator, seam sealer, can spray, brush on? can you recommend what to do first and products brand and name to use and in what order?

Please help,

Thanks,

Rodney

[jjeffries]

Rodney, you should wait until someone more pro than me advises, but I'd say to avoid rust encapulator products. You should look into products from a commercial supplier (Glasurit, PPG, 3M et al) for chemically treating (cleaning then protecting) these areas perhaps after whatever cleaning you can do with a cup wire brush on a 4.5" grinder or wire brushes on an electric/air drill. Hopefully you weren't thinking in this direction, but that project of yours should not get any POR-15 or similar applied to it. You can often download these manufacturers' catalogs to see what they have; just avoid "homeowner-grade" materials....they generally suck compared to the "good stuff".
I hope that helps. John

[Rodney Nelson]

Hi John,

Thank you for your reply. To clarify a bit, yes, I am going to use grinders and wire brushes to get everything possible. And I have already dipped the chasis, but there are all of these nooks and cranies that I feel are impossible to get to. So, the question is what is the next step to ensure all rust is dead. What about those impossible to reach cavities? What products are recommended for those areas?

For example if I'm installing one of the tank supports once welded in I can't get behind it to treat. Do I coat the back of it with something before I weld in? Weld through primer? ugh...

Thanks,.

Rodney

[lelix]

I prefer the following sequence for front end rust repairs.
Bare metal>epoxy>filler work if needed followed by a sealer coat of thinned epoxy to hide the filler>Seam sealer on overlapping panels>chip guard texture>another sealer coat if painting over chip guard since it can be rather porous > finishing topcoat as desired.

I would think you need to worry about 2 parts.
-How to clean and prep the chassis after the chemical strip

-How to seal new repair panels.

For the first (and most time consuming) part you need to make sure all the traces of the chemical strip are gone from the surfaces you are going to epoxy prime. The treatment of the bare metal will depend on the epoxy you are using. For example SPI advises against using ospho and rust converters prior to using their products since you can loose adhesion if it's not neutralized correctly. For the actual rust cleaning and surface prep, you will need to use a whole array of wire brushes, cupped wheels etc and do your best to get to all the seams etc. The rust pitting is best cleaned out by mild spot sandblasting or chemical conversion combined with wirebrushing to clean out the pits. Epoxy should still adhere well to pitted metal given the proper prep of the area. I would strip all the seam sealer you can, since it is already compromised by the chemical strip and may hold moisture,chemicals or dirt behind it. Follow the metal prep instructions to a tee for the epoxy system you will be using.

The second part would be the sealing of the repair panels. I like doing it in stages(i.e every new layer of the repair gets sealed with epoxy before a new layer goes over it). It will take longer but I feel it will have a better end product.
I would clean and epoxy the whole pan and the areas that will be covered first(areas under the tank supports, flanges etc). then only clean the areas to be welded, spray a light coat of weld thru on the "cleaned" areas(flanges and contact points), let it dry and do your welding (note that if you are doing a plug weld, weld thru may give you a real hard time to get a clean plug weld, in this case, clean it out from the hole you are about to weld up). I would not leave the bare galvanizing exposed as it will affect the longevity of the repair.

A good method for sealing the suspension pan flanges(as well as any other vertical seams) after you've welded them into the tub is to tape the bottom of the "pinch weld" and pour epoxy into the whole length of the seam. This should give you additional sealing and coat the rosette welds "inside" the seam. Epoxy can be brushed on easily so you do not need to spray it, that comes in handy for those hard to reach crevices.
If the back of the weld cannot be accessed after the install, it may be best to try and treat the inside of the cavity with an undercoating type spray OR try and spray epoxy through a "wand" type applicator. Most of the panels have some kind of access holes in them so it should not be an issue.

Hope this points you in the right direction even if some stuff I mentioned sounds obvious and redundant.
Cheers.

[Rodney Nelson]

Originally Posted by lelix

I prefer the following sequence for front end rust repairs.
Bare metal>epoxy>filler work if needed followed by a sealer coat of thinned epoxy to hide the filler>Seam sealer on overlapping panels>chip guard texture>another sealer coat if painting over chip guard since it can be rather porous > finishing topcoat as desired.

I would think you need to worry about 2 parts.
-How to clean and prep the chassis after the chemical strip

-How to seal new repair panels.

For the first (and most time consuming) part you need to make sure all the traces of the chemical strip are gone from the surfaces you are going to epoxy prime. The treatment of the bare metal will depend on the epoxy you are using. For example SPI advises against using ospho and rust converters prior to using their products since you can loose adhesion if it's not neutralized correctly. For the actual rust cleaning and surface prep, you will need to use a whole array of wire brushes, cupped wheels etc and do your best to get to all the seams etc. The rust pitting is best cleaned out by mild spot sandblasting or chemical conversion combined with wirebrushing to clean out the pits. Epoxy should still adhere well to pitted metal given the proper prep of the area. I would strip all the seam sealer you can, since it is already compromised by the chemical strip and may hold moisture,chemicals or dirt behind it. Follow the metal prep instructions to a tee for the epoxy system you will be using.

The second part would be the sealing of the repair panels. I like doing it in stages(i.e every new layer of the repair gets sealed with epoxy before a new layer goes over it). It will take longer but I feel it will have a better end product.
I would clean and epoxy the whole pan and the areas that will be covered first(areas under the tank supports, flanges etc). then only clean the areas to be welded, spray a light coat of weld thru on the "cleaned" areas(flanges and contact points), let it dry and do your welding (note that if you are doing a plug weld, weld thru may give you a real hard time to get a clean plug weld, in this case, clean it out from the hole you are about to weld up). I would not leave the bare galvanizing exposed as it will affect the longevity of the repair.

A good method for sealing the suspension pan flanges(as well as any other vertical seams) after you've welded them into the tub is to tape the bottom of the "pinch weld" and pour epoxy into the whole length of the seam. This should give you additional sealing and coat the rosette welds "inside" the seam. Epoxy can be brushed on easily so you do not need to spray it, that comes in handy for those hard to reach crevices.
If the back of the weld cannot be accessed after the install, it may be best to try and treat the inside of the cavity with an undercoating type spray OR try and spray epoxy through a "wand" type applicator. Most of the panels have some kind of access holes in them so it should not be an issue.

Hope this points you in the right direction even if some stuff I mentioned sounds obvious and redundant.
Cheers.

Hi Lelix,

Thank you this is what I was looking for.

[jjeffries]

Lelix, great description. Should be a Sticky. John

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