Looking for advice. The car is at bare metal and the next step is epoxy sealer followed by k36 sandable primer etc. i have used a variety of phosphoric acid concoctions to turn pits or crevices to black iron II. But on sanded bare steel it leaves a grey haze at best, and a slightly orange have at worst. I am not a friend of iron oxide under my paint.
With all of that said, i know that a lot of folks etch prior to paint. In my hands that hazy stuff makes me nervous. Will it adhere as tightly to the paint and steel as the epoxy would without the etching. My chemistry knowledge is stronger when you have a bunch of carbons to play with. So any help would be appreciated.

I’m Confused.

If at bare metal - sealer is not the first thing to go down under primer onto metal. Maybe I’m misunderstanding what you meant?

Regarding etch. Properly done, etch will be slightly gray - no longer shiny metal. Should not be rust or orange.

Trick to etch is do only a small area. Etch, rinse, dry immediately.

If you can’t master that - start with shiny bare metal and source a self etching primer. Edit: not pointing fingers at you - high humidity or other corrosives in your shop can cause the flash rust / orange haze.

Sealer goes between primer and topcoat for PPG systems I’ve used.

Tech sheet is your friend.

K36 can go over Delteon self etch primer.

Click to view attachment

If you have a local paint shop I recommend buying your products through them (if doing it all yourself). They’ll be able to sell you compatible items, and give you some good advice. I did that when I painted my car and haven’t had any weird issues.

And agree, scour the tech sheets.

It's a system that needs to work together.

Use this stuff it sticks like no tomorrow you can 60 grit your deep dents and bondo or lighter for top coat filler and any primer will adhere well Click to view attachment

DP40 and DP402LF is the first thing to go on the steel. I am very fond of PPG epoxy. PPG thinks that is perfectly ok under K36. But I misspoke. It does seal metal from moisture, but isn’t a color sealer. Do you think because I am *not* using an etching primer that I should use a metal etch?

You can use epoxy over freshly sanded and cleaned metal. You then do primer surfacer or any body filler over that then seal and paint(I use epoxy primer as a sealer)

Ditto. What he said!

Ditto what I have been doing for the past cars. I have had no troubles with epoxy, surfacer, paint. But wanted to know if I could do even better by etching.

People etch prime when they are are painting over previously rusted metal. It helps to chemically bond and seal up the micro pitting that you can’t get to with sanding, etc. I’ve always heard the rule of thumb is epoxy over fresh metal and etch prime over previously rusted metal. But I’m no painter so follow the tech sheets.

Factory did etch primer, build/filler, sealer, then paint. Anything else and your gonna regret it. Etch has phosphoric acid (self neutralizing) and also seals with the solids in the paint. Second best thing to a true galvanized body.