What about using paint as primer?

attackpilot · #1 12-10-2006, 11:40 AM

Hello Everyone:

Not to re-start the "Should I prime/Should I not prime?" debate, but I have a question. With all the discussions on how primer is not a sealer and only zinc oxide protects, blah, blah, blah, etc. I am wondering how just regular enamel paint would act as an interior "primer" and sealer?

I have been using NAPA 7220 very sparingly (generally in enclosed areas where two pieces of metal meet) on the tail. I am about to move onto the QB fuselage and would like to protect the area below the floors from spilled drinks and whatever else ends up down there. I would really like to avoid having to prime, then seal, then paint if possible.

I read something to the effect of how some custom car body shops don't remove all the paint if they know there is no rust because the paint is better than the primer they would spray on. Plus enamal paint is generally cheaper than any primer.

Any thoughts?

Joe Hutchison
RV-10 Tail Kit & QB Fuselage

KTM520guy · #2 12-10-2006, 12:20 PM

One one the reasons primer is used is to help the paint stick to the metal. Primer sticks to metal a whole lot better than the paint does. Paint sticks to primer really well. With out primer, paint will some day blister and flake off.

Kyle Boatright · #3 12-10-2006, 01:00 PM

On Van's original RV-6, they painted the aircraft without using primer. Keeps the empty weight down, you know. ;-)

A couple of years later, they raced the aircraft in the Sun 100 at Sun and Fun. When they removed the temporary vinyl race numbers, the vinyl took big chunks of paint with it.

I recommend primer under paint.

vlittle · #4 12-10-2006, 04:42 PM

I used Tremclad aka Rustoleum grey enamle spray paint on my engine baffles.
Scuffed and cleaned the aluminum, let the paint harden for 24 hours and its works extremely well. No flaking or peeling in a very demanding application.

This paint is designed to spray directly on metal without a primer. I'm sure it's not as good a three-step systems, but works for certain applications.

The colour almost exactly matches the Van's Seattle Grey powder coat.

Vern Little

szicree · #5 12-10-2006, 05:41 PM

I think the issue is that you need your coating to do several things: Stick to bare metal, inhibit corrosion, seal out moisture, stand up to UV and abrasion, maintain gloss, and come in lots of cool colors. It would appear that such a do-all product has yet to be invented.

alpinelakespilot2000 · #6 12-10-2006, 08:35 PM

Speaking of needing/not needing a topcoat, does anyone recall which RVator (sometime in the last 2 years) had the article explaining why non-sealing primer coats alone were more than sufficient? I've been meaning to find it for a friend. I seem to remember that in it they described an informal test using their regular SW primer that showed it provided good protection by itself, even if SW said it technically needs a topcoat for maximum protection.

vlittle · #7 12-11-2006, 09:08 AM

Quote:

Originally Posted by alpinelakespilot2000

Speaking of needing/not needing a topcoat, does anyone recall which RVator (sometime in the last 2 years) had the article explaining why non-sealing primer coats alone were more than sufficient? I've been meaning to find it for a friend. I seem to remember that in it they described an informal test using their regular SW primer that showed it provided good protection by itself, even if SW said it technically needs a topcoat for maximum protection.

I don't recall the article, but I talked to an engineer at Sherwin-Williams about their vinyl wash primer.

He said that it would 'lock up' and provide a moisture barrier, but due to it's thinness, there is not a lot of mechanical durability. I use the zinc chromate version of this primer. I'd use it again anytime... Just clean the metal and shoot the primer-- no scuffing necessary. Please no primer wars, it's just what I did.

Vern