Prep before paint questions

[wimberosa]

This is posted separate from my build thread in the hope of getting more opinions.

At this point I've finished all patches to my 1979 tub. I'm in sandblasted form but I have
residual oil, white cruft from ospho, and other cruft hanging onto bare metal.

I have basically two questions that I'm unsure on.

1) What prep and finish should I do on channels such as inside rocker panel, bed channels, etc.
2) What steps would you suggest for getting this clean and ready for paint.

Regarding question (1) ... I'm wondering if I should attempt to treat the inside of channels with rust converter,
whether to apply any other cleaner, should I attempt to epoxy coat the inside of those channels, should I go with
just a cavity wax? Some of those channels such as the rockers have some original OEM tar on the inside and I
know I've burned some of it with weld patches....So I do have some exposed metal on the inside. Furthermore as with
all other seams...there's probably some latent surface rust that I'd like to sequestor and stabilize.

Regarding question (2)...I'm wondering if I should power wash it with water and perhaps clean it with dawn soap.
I'm slightly worried about flash rust or getting water in seams that currently are ok....but may develop rust with water.
I could spray it after washing with something like 50/50 krud kutter rust remove combo with water and that stabilizes it if I put a lot on .... but then i end up with this crufty residue from that flash rust preventer. I've run tests with brake cleaner and final prep cleaner but
I'm just not super happy with how clean I'm getting it.

Regarding question (2)...also I'll hit it with some final Klean Strip Wax and Grease remover just before epoxy paint application.

A pic of what the tub is looking like currently.

 

[South Texas 97]

Not an expert, but if you have OEM tar on channels, you can’t really paint that, so perhaps cavity wax is the way to go.
Every thing else the 50/50 Krud cutter rust restore, and then clean the crud off just before prepping for epoxy paint.

 

[Pitter Patter]

So stoked you’re done with body work!!! Don’t power wash it. Sounds like you are doing your own paint? If so, there are paint options for cavity areas with flexible 360 degree sprayers. As for cleaning, just use a paint prep with a wax/grease remover. It’s a tedious job but nothing compared to the body work.

Just remember, it was 40ish~ years old when you started this process. Whatever work you do will outlive you.

 

[DKM]

This is posted separate from my build thread in the hope of getting more opinions.

At this point I've finished all patches to my 1979 tub. I'm in sandblasted form but I have
residual oil, white cruft from ospho, and other cruft hanging onto bare metal.

I have basically two questions that I'm unsure on.

1) What prep and finish should I do on channels such as inside rocker panel, bed channels, etc.
2) What steps would you suggest for getting this clean and ready for paint.

Regarding question (1) ... I'm wondering if I should attempt to treat the inside of channels with rust converter,
whether to apply any other cleaner, should I attempt to epoxy coat the inside of those channels, should I go with
just a cavity wax? Some of those channels such as the rockers have some original OEM tar on the inside and I
know I've burned some of it with weld patches....So I do have some exposed metal on the inside. Furthermore as with
all other seams...there's probably some latent surface rust that I'd like to sequestor and stabilize.

Regarding question (2)...I'm wondering if I should power wash it with water and perhaps clean it with dawn soap.
I'm slightly worried about flash rust or getting water in seams that currently are ok....but may develop rust with water.
I could spray it after washing with something like 50/50 krud kutter rust remove combo with water and that stabilizes it if I put a lot on .... but then i end up with this crufty residue from that flash rust preventer. I've run tests with brake cleaner and final prep cleaner but
I'm just not super happy with how clean I'm getting it.

Regarding question (2)...also I'll hit it with some final Klean Strip Wax and Grease remover just before epoxy paint application.

A pic of what the tub is looking like currently.

View attachment 3653043

I am thinking just give some passes with a pipe brush, blow it out, then spray with one of those 360 degree tubes from eastman and hit it with rust converter/encapsulator, after paint I'll hit the channels and tough spots with fluid film. Let me know if you get some tips that you could share!

 

[Skreddy]

I wouldn’t use water on it unless you properly neutralize it which sounds like a science, so I’d just avoid water.

The Ospho will clean off with more Ospho. Just spray the crusty areas and let it sit long enough to soak those but not long enough to start drying, then wipe off. Like a minute usually works.

Never used the Eastwood cavity stuff but I know people who have and are happy. In my opinion, if there’s rust or water in the cavities it doesn’t matter what you spray in there because it’ll only coat it, not kill it. In the last one I painted, I sprayed some Ospho in the areas I couldn’t paint and left it at that.

Any tar, undercoating, etc. I’d try to get off mechanically by sandblasting or sanding, otherwise chemically by acetone or something. Then a good wax and grease remover over everything until the wiping cloths are pulling up clean.

 

[wimberosa]

I've not tried the eastwood internal frame coating but it sounds promising. I HAVE tried
their rust converter and it appears as if its trying to be a primer and rust converter combo. However
after I put it on and let it cure...i wiped it with brake cleaner and it comes off. My take on the rust
converter is that it looks like it would fail as a "primer" to paint over. Just opinion.

So a combo of converter + direct paint with the eastwood internal frame coating may be better for channels.

I picked up cheap TCP undercoating gun off amazon and intend to follow up the "convert rust + paint" aspect of treating the channels with a cavity wax finish. If I really get ambitious a yearly fluid film addition to in the wheel well areas would be a plus. The rib in the front wheel well and the braces in the back wheel well for the roll bar ... look like particularly bad areas to trap moisture.

On other fronts I'm looking for a combination epoxy primer + high build primer as an underlayment for
what I believe will be a RM UNO HD single stage topcoat. @73FJ40 sparked my interest on the RM UNO HD paint a few years ago.