I am preparing to paint my 1953 F-100 cab. If the weather holds, I may even get to the bed and fenders. I am attempting a stock restoration, so the finish will be acrylic enamel.The underside of the cab does not appear to ever have had any paint beyond a brown primer. There is some surface rust there which I am trying to remove, but I can't get it all. I am considering using a chemical rust treatment on the metal here. I have heard that I would not want to put any sort of topcoat over a rust treatment, but would epoxy primer and a coat of brown enamel here (so it looks like the original factory primer) work, or am I risking some sort of disaster? It's the bottom of the truck, so it'll be subjected to a fair amount of dirt and mud.I have been learning that there are many compatibility issues with different primers and paints. The 2k primer that I am putting over the epoxy on the rest of the cab is brown in color. Could I use that and leave it as a "topcoat" on the bottom, or does it require a real topcoat. I understand that some primers are porous and don't provide any rust protection. Is 2k like that? For the rest of the cab, the primer and topcoat, while both were purchased almost ten years ago (in a fit of work-related optimism), are still good to use. Unfortunately, both the primer and topcoat lines have been discontinued by PPG. The primer is DPLF Epoxy. The enamel is DAR Acrylic Enamel. Any rust treatment that winds up on a surface which will get the enamel will be cleaned off to bare metal. Any advice or comments?

 

Depends on your rust treatment. I can tell you for absolute certainty that Picklex 20 can be used to convert the rust you can't remove. The key with these things is the primer since acid based primers will react adversely with the surface. DPLF is not an acid based epoxy so you will be good.

For the bottom I would clean to bare metal, use Picklex 20, spray 2 medium coats of DPLF, and then 2 medium coats of your color. Don't bother with 2K primer in the middle since there is no reason to block sand the bottom anyway. However, if being correct, you could leave it in just the epoxy primer. DPLF 74 is red oxide in color and would look good on the bottom.

 

Thanks, Tbm3fan for your response. It has started to occur to me that I may not get all my body parts ready for paint before the cold weather gets here. So, I'm thinking that, per your recommendation, I coat all the bare metal pieces with PickleX 20 and with any luck, get paint on them sometime next spring. I have some questions about Pickle X. There are some places where sheet metal panels are joined by spot welds. One example is where the roof skin joins the back panel of the cab. I have abrasive blasted, wire brushed, and / or sanded the cab, but there is still that thin rust that has grown between the two panels over the last 60 years. Will Pickle X penetrate these seams and neutralize the rust here? And next spring, I will have to clean up the pieces prior to painting. If I scrub the parts with detergent, rinse them with clean water, and finish up with a degreaser, I guess I'll be removing the Pickle X. I am nervous that water may enter the seams and be absorbed by the rust or the now converted rust. Should I be concerned about this moisture? I can use a heat gun and compressed air to do my best to dry out these seams. Is that how this is usually handled? I assume any Pickle X treatment on the bare metal will be gone by the time I finish cleaning stuff up, but I assume that's okay. When it's all dry and ready to paint, I'll be using the PPG DPLF epoxy primer. I read on the SPI site that I should sand with 80 grit all the surfaces that will get primed. It's probably pretty clear by now that I am a novice at painting.

 

Picklex can last the entire winter in a garage if the metal doesn't get wet. Water will rinse off the protective coating it places on the metal.

Picklex can penetrate the seam if you use it with a painter's/modeler's brush. As always the stuff is rubbed into the metal and any excess removed with the quick wipe of a paper towel. You could then brush in some DPLF since spray really doesn't get into seams well. Then put your seam sealer next before painting the cab.