Paint Peeling Challenge

[bdflyer]

Ok. So i got the rear of the plane all primed and painted (on the inside) and while I was blowing out some aluminum shavings, I ended up seeing the paint peel off.

The surface was cleaned, the paint did not ripple - looked fine. Just when a standard air blower off my compressed air tank was used, it peeled up.

Thoughts on a cause? I used a solid etching primer (Dupli-Color Pro Automotive Primer), and then a top coat with a basic Rustoleum pro black enamel.

5777

[wltrmtty]

Did you use a self etching primer under the paint?

[bdflyer]

Yes, I used a solid self-etching primer (Dupli-Color Pro Automotive Primer).
http://duplicolor.com/product/self-etching-primer

All I can think of is that I should have buffed with a good sandpaper prior (sigh - its on my checklist...)

[Kyle Boatright]

Yes, I used a solid self-etching primer (Dupli-Color Pro Automotive Primer).
http://duplicolor.com/product/self-etching-primer

All I can think of is that I should have buffed with a good sandpaper prior (sigh - its on my checklist...)

Self etching primer should stick much better than *that* even to un-scuffed metal if the metal is clean. That said, a scuffing with scotchbrite is recommended and will promote adhesion.

I'd do some test coupons to see if that primer sticks to scuffed aluminum before I used it again.

[vaflier]

Red scotchbrite pad not sandpaper. Steps are as follows , Clean and degrease, scuff, clean and degrease, acid etch, alodine, epoxy primer, topcoat. Oversimplified but you get the idea. Looks like the primer did not stick at all. Start over. Boy that bites.

[martymayes]

Duplicolor aerosol products are not what you would use in the same sentence as quality. From the SDS it looks more like flat lacquer, lots of solvents with just a touch of pigment. From the photos not much etching took place.

I would avoid using sandpaper and even scotchbrite on a new surface.

[Matt Gonitzke]

I would avoid using sandpaper and even scotchbrite on a new surface.

What's wrong with scotchbrite? Lots of factory-built airplanes have parts roughed up with scotchbrite wheels before primer is applied.

[Aaron Novak]

Red scotchbrite pad not sandpaper. Steps are as follows , Clean and degrease, scuff, clean and degrease, acid etch, alodine, epoxy primer, topcoat. Oversimplified but you get the idea. Looks like the primer did not stick at all. Start over. Boy that bites.


Yep thats the best process, anything else is just taking shortcuts.

[martymayes]

What's wrong with scotchbrite?

It is the same as sandpaper, the paper backing replaced with spun polypropylene fiber. They both use aluminum oxide as the abrasive.

It's like saying: "Don't drink water - use this H2O product instead!"

[martymayes]

Red scotchbrite pad not sandpaper. Steps are as follows , Clean and degrease, scuff, clean and degrease, acid etch, alodine, epoxy primer, topcoat. Oversimplified but you get the idea. Looks like the primer did not stick at all. Start over. Boy that bites.

That's well and good but an alternative method is to simply clean the surface with the proper solvent and spray on a product like "Don't Punt" Verri Prime. It can etch and adhere to a porcelain enamel finish with minimal prep (clean and degrease). Having used the old methods for ~40 yrs. I'm inclined to embrace technological advances in this area.

[Bob H]

If you use Scotchbrite, be sure to solvent wipe with acetone before applying primer as it can leave residual particulates.
From pic, primer did not adhere at all which indicates poor surface prep procedure. Solvent wipe, abrade surface, solvent wipe again and prime.

[martymayes]

If mechanically etching the surface, no need for self-etching primer. It's a waste of money. If chemically etching the surface, follow the instructions. Probably will say to skip mechanical etching.