Which comes first?

[Jhn824]

So here's a question for you modern body and paint guys... back in the days of siphon spray guns and lacquer paint... most of the body and filler work was done on bare metal... now it looks like most people put down epoxy primer and do body work on top of epoxy...and then finish off with sealer primer just before paint... is this right?

 

[Builderguy]

I take the car to bare metal and then spray with epoxy to keep it from rusting. Then I can work on it at my leisure. I still take it down to bare metal before I do any significant repairs. I am of the opinion that fill sticks better to bare metal. Once the filler work is done, if there is bare metal I will again shoot it with epoxy. Then, within the window, I will shoot some high build primer on it. Let that set up and then start sanding. I fill the lows with glaze and tap down the highs. More coats of high build and sanding until the guide coat shows it is all smooth. Then seal whole car with the color recommended for the base color I am going to use. The biggest pain is sanding the epoxy, tends to gum up the paper and you have to sand it if you are out of the window. There are other ways to do it, this is mine and it works for me.

 

[Jerry Hall]

Any bondo work we do is to bare metal and as little as possible. It is not uncommon for a car in our shop to be left in bare metal for up to a week or two with no rust problems. Just don't walk by and touch it, that will just about automatically start the rusting process.

 

[Jhn824]

thanks guys... any recommendation about metal prep/rust treatment before epoxy (for panels that have been stripped?)

 

[Builderguy]

After stripping there should not be any rust left. If you are talking about areas you can't get to (like the inside of a rocker panel, or inside of a boxed panel, etc) that is a tough one. I have used POR 15, Rust-oleum Rust-Reformer spray, and Evapo-Rust in the past. I like POR 15 for the frame and Rust-reformer for metal areas I can get to. Evapo-Rust can be poured into areas I can't see and then roll the part/body around to coat what you can't see. Never said this was easy.
Panels that are already bare, just sand them again to bring back fresh metal. If they are fairly clean but maybe a hand print where very light rust has started I have used plain old distilled vinegar on a rag to wipe the panel down. Remember to neutralize with baking soda and water and then dry completely. I still sand after this treatment as it is just to remove very light rust. Wipe the bare metal down with something like PPG Shop-line JX101 or some other wax and grease remover prior to spraying the epoxy. The epoxy I use PPG JP377 which uses this grit: "Sanding 120 - 180 grit on bare metal, before JP37x Epoxy Primer 220 - 320 grit on old finishes, body filler" direct from the data sheet. Use the data sheets for your products. They are your friend and will save you time and headaches. Good luck on your project.

 

[vintage chromoly]

Epoxy on bare metal and body work on top of the epoxy.
After the body work is done, epoxy (mixed as a sealer) is applied before the color.

 

[snakeoil24]

I media blast to bare metal. Then clean as much media out as possible. I clean with prep solv then apply two coats epoxy. Then all body work is done. Follow with 2 more coats epoxy to seal body work. Follow with 2 coasts sandable primer. Block, block block. Then 2 more coats sandble primer with every effort not to break thru to epoxy use adifferent shade to see when you get close. Follow with sealer. Then color usually 3 coats. Clear coat 2 coats then wet sand and three more coats.