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I am curious what type of paint was used on the 1951 chassis. I scraped and used mineral spirits to remove the undercoating (tar). I tried a paint stripper afterwards to remove the paint and while it softened the paint I had to use some scrubby pads to remove it. Having some furniture "restorer" I tried that and it immediately liquified the finish. The container said it contained Methanol, Toluene, and Acetone. I am guessing the finish was lacquer.I would like to know so I can get the proper stripper as the furniture restorer I had is no longer available and I still have lots pf paint to remove.

Is the frame still under the car?

Mike

The frame paint was an utility grade enamel.

To clarify I am actually stripping the inner fenders right now, The frame has been blasted and painted. Usually with enamel with stripper it bubbles up and can be mostly scraped off. The paint on the inner fenders does not bubble at all no matter the amount of stripper.

The real issue is what is left when you remove what is currently on there. That is what your new primer paint need s to stick to. If you are using an etching primer, any film left might interfere with the etching mechanism that allows the primer to stick to the metal. If you are using an epoxy, you need to mechanically attach the primer by sanding the metal.to 80 grit sandpaper.
If the primer fails, so does the finish coat.

Mike

Thanks for the info Mike. Right now I have one side (inner/outer) stripped , washed, acid etched, and washed again to neutralize. I am thinking of Epoxy priming and painting both sides and possibly undercoating the wheel side with a hard bedliner coating. Will cross that bridge when I get to it .

If you read the tech data sheets for epoxy, it recommends that you sand the solid surface with 80 grit sand paper before epoxy priming…… because of this, there is some question about use of products like Ospho to de rust the surface. I believe it’s because it messes up the bite the sanding imparts to the metal. I should think that you could use derusters to hold back rusting until you sand and epoxy prime. I believe putting something between the etching primer and the metal causes similar problems.
I believe Epoxy primers are the only water proof primers and the closer to the metal they get, the better the protection.

I personally use PPG products (I don’t like mixing brands) and use ALK 200, a single stage enamel for the finish frame coat and underneath. It’s an industrial grade product….. It also makes a nice finish for some older cars and doesn’t give it the wet look of a basecoat/clearcoat finish. Some of the old Chevy parts suppliers sell this.

Mike

I am using the acid after glass beading to prevent flash rusting. The de-rusters I believe require that the rust be present to be effective. If there is no rust then the "conversion" does not happen and no drying takes place. It then has to be wiped/cleaned off. The phosphoric acid has been working well for me for the smaller parts. They body and larger parts -hood-trunk lid-doors-fenders- have been glass bead professionally blasted and zinc phosphate coated . Yes I do know sanding will be necessary and one shop I know hit everything with 40 grit to get good "bite". I do not plan on doing the major painting myself.

Actually the acid treatment also increases the surface area similar to sanding. The higher the surface area the better the adhesion of a coating. The additional coatings are formulated to adhere to the primers. If you have questions on the compatibility and expected life of additional coatings contact the manufacturer and/or experienced professional painter. The recommendations commonly are to only use products from the same manufacturer.