Working on repainting the roof of my truck given it was first with a failed clear coat. Without time to mask and prime for a couple days, I became concerned for a metal prep, and a quick online search returned some recommendations for using diluted white vinegar. After the effort at patching some holes and sanding out most of the rust beasties, I had become concerned for protecting the metal from moisture at night.

To my horror, however, in less than a matter of minutes after applying vinegar, the bare metal turned a deep rust-colored orange that when wiped, deposited significant material onto a rag that seemed to be the metal breaking down before my eyes. I quickly wiped everything down with water several times then dried, sanded and scoured everything until the metal seemed to be restored to a new layer. This was not easy however because the orange hue seemed to get underneath the paint where I had not sanded to bare metal.

Would this actually be a beneficial reaction, so long as one is ready to prime directly after? Is this reaction actually evident of the ascetic acid doing the work of etching the metal that might cause devastating oxidation if left bare but is actually helpful to a coat of primer? I tried something similar with phosphoric acid after cleaning up rust in the windshield channel, but again the cured phosphoric acid (or the metal underneath) started turning a rust color not long after the 24hr wait time before primer. At this point, it is my sense the best one can do it to thoroughly sand, wipe with nothing other than water, then prime as soon as possible.

Once metal is sanded it needs nothing but epoxy primer over it.
Sand it clean, tack off the dust and prime it.
Washing with anything, especially water, just means you need to sand it again
before primer.

Never used vinegar. I wipe down rough surfaces like welded seams and surface rust with phosphoric acid based descaler but I also immediately rinse and scrub the area with windex (because it’s water based and will carry off the residue). Otherwise for flat surfaces without surface rust, I just sand and wipe like the previous person mentioned. I mean, I still sand on rust but sometimes that’s not enough to loosen up all the surface rust in spot welds and recessed areas.

I take extra caution to keep over-spray limited with the acid by either brushing it on or using a rag with some pre-soaked in it.

With all that said, I’m an amateur so If someone says I’m an idiot il accept the criticism.

The only thing you should be wiping bare metal with is a solvent based automotive wax and grease remover. That is sprayed on and wiped off with a clean shop towel BEFORE it dries.

Phosphoric acid will cause adhesion problems if not properly neutralized. Acetone, paint thinner, auto prep, etc. are all going to leave some film behind that will also cause adhesion problems.

Usually, like JCClark stated, you sand the metal (DA with 80 grit works) and then using a quality tack rag (no wax soaked nonsense) get the surface free of dust. Shoot two coats of a quality epoxy primer and then let it set at least 24 hours.

Vinegar? As a complete rookie, I have learned to bug the experts on this site and to stay off of YouTube and FB among other places for information.

Search this site first then ask if you haven't found what you are looking for. Trust me, you can save thousands of dollars (you can also spend thousands!!) using this site's information.

OldFatBald wrote: Trust me, you can save thousands of dollars (you can also spend thousands!!) using this site's information.

save an hour or 83 of redoing work that was done by following YT "experts",too.

Glad to be here connected to folks with experience rather than out on search results that will tell you that anything that is queried is true. Not totally familiar with wax and grease remover, though would denatured alcohol be a viable alternative? I seem to remember this is the only common solvent that does not leave a residue.

Here is the primer that I have, though would an epoxy primer imply that it is an enamel base? I am new to considering the various primers ranging from rust-inhibiting name brands to automotive grade, lacquer/enamel/epoxy, etc.

I do not have a proper spray gun / compressor setup, but would this be about as good as I can get in a rattle can? Included are the contents -- would these give any hints as to the chemistry or whether I ought try to find an epoxy version?

Well, if you plan on actually painting cars, you need to be ready to spend some money on a good compressor ($2000), a filtration system/water separator, air regulator, air hose, spray guns, painter's suit, mask with charcoal cartridges, gloves, tack clothes, multiple sanding blocks, sandpaper, masking tape, masking paper, masking film, guide coat and some quality primer, paint and clear.

Right now, you are wasting time and money.

I started out like you and wrote an article to help others just getting into this and wanting to do it right.

https://www.autobody101.com/content/art ... ould-know/