Have a late 80s Pinarello Montello that I'm refinishing myself as a learning project. Beautifully stripped and sanded down, cleaned thoroughly with acetone a few times. I'm having difficulty getting the primer to adhere properly. Temperature is good, a few days between coats, followed the the manufacturer's instrucions very well, but the primer (Motip car primer) can flake off pretty easily and I'm apprehensive moving to the main coating. Any recommendations?

I had good luck brushing muriatic acid on the bare frame before the first coat of primer. AND wait at least 1 week between thin coats.

https://www.duplicolor.com/en/produc...etching-primer

I have only done one frame, and that was my first time painting anything other than water color, so my advice is worth about what you'd think, but I think primer not adhering would make me restart. I used Rustoleum Stops Rust self-etching primer, and it adhered extremely well. I'm not advocating Rustoleum necessarily, because I understand one should use primer that corresponds to the paint type you'll use. I'm just saying that in my limited first hand experience, the primer didn't flake off. My two cents.

Maybe the acetone didn't fully evaporate? Dunno, I just always see folks advocating acetone as something to use to remove paint, so perhaps it's affecting the primer's ability to adhere. I did mine a couple of years ago, and I remember using rubbing alcohol to clean the frame just before spraying the primer. (Sometimes rubbing alcohol is sold mixed with acetone, but the one I used was not.)

^^^^
There should not be any issues when applying primer to a bare steel surface. If there is an issue with the primer adhering to the frame, there must be oil residue present....re-strip the primer and wipe the frame down with acetone and re-spray again.
Best, Ben
BTW, Oil from your hands may cause problems along with wiping frame down with an oily/dirty rag.

Self etching or auto primer with the acid additive.
my suspicion is that the surface is too slick and something was introduced that the acetone is not clearing.

acetone is not a panacea

Scuffed with 220 grit?
Bad can of primer?

try a paint prep cleaner....then only touch frame with gloves on

acid etch primer..... then sandable primer

I'm guessing that your Montello is fully chromed. You may need to use a coarser sanding and follow up with filling primer to get a smooth surface. There's a reason that these are notorious for losing their paint.

Well if it is fully chromed then that answers the question about primer adhesion...........Chrome and paint are not friends, It will take a lot of scuffing to get it to adhere properly.
Good Luck, Ben

My PX-10 had a fully chromed fork. Sanding and the muriatic acid got it ready for brushed on Rustoleum.

There were no images to reference what is going on.

as someone mentioned, human hand oils can effect things too. I had a colloge design professor who asked to touch the hands of each student. About 1/3 of the class he declared, “you have a problem”
oily hands, it will take an exceptional effort to not turn in shabby appearing work.

Another vote for self etching primer. Nothing else seems to work as well.

I'd love to see an example of the label on such a retail item.

I can't conceive of why such a combination would ever be sold to the public. Acetone is a powerful solvent, enough to de-fat your skin should you use it to clean your hands. It's also fairly toxic, both in liquid and vapor form, not something you'd want coming into contact with your eyes or your breathing apparatus.

What's commonly sold as 'denatured' alcohol isn't 'rubbing' alcohol so maybe you're confusing the two? Rubbing alcohol's a solution of isopropyl alcohol (commonly sold in either 91% or 70% concentrations) diluted with distilled water. Safe enough used on your skin but NOT to be taken internally.

Denatured alcohol is ethyl alcohol (ethanol) with any one or a combination of additives added to make it rather toxic so as to avoid it being taxed as a beverage. Most common 'denaturing' agent is methanol (wood alcohol), which can blind you if taken internally.

A little off topic, but here is a link to "rubbing alcohol" that has acetone listed as an inactive ingredient on the back panel. To your point, it is clearly labeled on the front as ethyl rubbing alcohol, but it's being sold as an antiseptic nevertheless: https://www.cvs.com/shop/cvs-health-...-prodid-304659

It doesn't matter to me one way or another, but there it is. I was surprised when I bought some recently and smelled acetone when I used it; had to check the label. I must have used isopropyl alcohol back then, and it's what I prefer to have in my medicine cabinet.

Just get a whiff of nail polish remover . . . sold by all and sundry.

Interesting. Thanks for that CVS link.

I did some Googling after posting what you replied to above, just to see if I could find references for what you'd suggested was available. Curiously, the only link I found was to that CVS product. There aren't any CVS stores anywhere close to where I live and shop so I'd never have encountered this product w/o seeing your initial post.

Acetone's cheap enough I have to wonder if it's used as an adulterant / denaturing agent for the otherwise 'drinkable' ethanol their rubbing alcohol product is formulated with? In proper dilution it's likely safer than the more common methanol used in commercial 'denatured' alcohol products used for various purposes, which is best kept from contact with your skin.

More in that noxious product than just acetone, but I agree.

Keep in mind that acetone is an organic solvent, a ketone actually, with the smallest molecule of any in that group. Our bodies make the stuff in minute quantities that then gets expelled in our urine. "Acetone is produced and disposed of in the human body through normal metabolic processes. It is normally present in blood and urine."

Here are the steps I used on an aluminum frame to get the surface primed per a spreadsheet I kept:

Day 1

Surface Prep
Scuff surface – 3M Very Fine, 220 Grit, Hand Sanding Pads – Red
Blow off – Blow Off Duster
Clean/rinse – Distilled Water
Dry – Clean, Fresh Towel

Day 2

Glass cleaner – Stoner Invisible Glass Cleaner (*use only a residue-free glass cleaner or skip this step if one is not available)
Dry – Clean, Fresh Towel
Clean & etch – Krud Kutter – Metal Clean and Etch
Rinse – Distilled Water
Dry – Clean, Fresh Towel

Day 3

Tap/block off – 3M Auto Tape and 3M Blue Tape – Bottom bracket, head tube *Block as you see fit
Insert screws – Screws in Bottle cages (4), front derailleur (2), rear derailleur hanger (1), rear chain stay (2), pump holder (Q-tip), seat post clamp (1)
Clean – Isopropyl Alcohol (70%) w/ Clean Fresh Towel

Etch Primer
Remove dust/lint – Blow Off Duster or Tack cloth (not needed, can leave a residue if not used properly)
Apply etch primer – SEM Etch Primer 2-3 light coats only to hide, 5-10 mins btw coats (flash), 10-20 minutes to top coat
Dry – Air dry for 30 mins to 1 hour

Surface Primer
Apply primer – SEM High Build Surface Primer 2-3 medium coats, 5-10 mins btw coats (flash), 1 hour to dry

** only handle frame/fork wearing nitrile gloves (disposable heavy duty)

Water dissolves more things than acetone.

Acetone has more punch than isopropyl alcohol or methanol but it's not that powerful. MEK, MIBK, isopropyl acetate and isobutyl acetate work better. Trans 1, 2 dichloroethylene, Trichloroethylene, Methylene Chloride and the late, lamented AK-225 were a step above those. DMSO has pretty much everything beat.

Yes, but that's also true for Dawn dish detergent.

Acetone is not that toxic. I'd much rather work with it than methanol, benzene or toluene.

Motip's formula doesn't use a super-aggressive solvent blend, and it doesn't appear to be self-etching. If your Pinarello is chromium-plated, the Motip primer may not have enough anchorage to the chrome. The usual solution is to sand or media blast, solvent-clean and then use an etching primer. Not sure if you can get formulas like the Duplicolor where you are, though.

Glass cleaner:

Never use "Windex", it leaves a residue.

(Personally I would skip that step)

It might be unnecessary, but I performed this step because I didn't have a dust-free/clean-air location and the frame and fork were hanging overnight in my garage during a time with a lot pollen. I lightly sprayed it into a cloth and wiped sparingly.

You are correct, though, definitely do not use “Windex” or a regular glass cleaner; I specified Stoner Invisible Glass because it's residue-free.

Per Stoner's website: “Invisible Glass contains no added soaps, scents, or dyes – all of which leave behind a filmy residue. Our cleaner evaporates quickly and completely, leaving no streaks or haze on surfaces. Tested and proven to be 100% residue-free by independent laboratories.”

https://invisibleglass.com/collectio...window-cleaner

I'm pretty sure I even contacted them to confirm. Regardless, the Krud Kutter – Metal Clean and Etch will also clean up anything left behind. I should clarify however; I'll update my original post. Thanks.

Thanks everyone. The frame is chromed, which appears to be contributing to the issues. It was very well sanded, as this was round two with the primer. Don't feel like I could do much more there. I'll take the advice, strip it again, clean with rubbing alcohol instead of acetone, and try a self-etching primer.

Have you considered abrasive blast on the chromed surfaces to be painted? And not walnut shells, but something mineral. I don't think that self-etching primer will make much of a difference unless the chrome is abraded sufficiently to give it a clearly visible "tooth".