Ultra low temp curing powder coating

[Tom Downey]

Tom,
Thanks for bringing up a reminder. The epoxy primers need to be baked before topcoating with powder, usually done at 400F for about 10min after the curing period.

And there are URA and epoxy powders that are applied with great success on bare steel, aluminums, and mag parts.
Steel needs a etch to remove and foreign substances such as finger prints, or other oils, dirts and debris. then heated for a pre dry period prior to powder application and final bake.
Aluminums are also etched with a 6% chromic acid, rinsed and dried prior to coating, same as any application of any protective coating Liquid or power.
As I worked at NUW as a master engine mechanic I helped NUW become VOC compliant in applying proactive coatings.
Powder coating was our Saviour in complying with EPA rules for emissions on paint booths.
When you apply Powder coating properly, it is far superior to any paint system in existence today. and there are no powders that require temps to apply that will harm any metal parts in todays aircraft.

You may have privy to many lad results at Your facility but I'll match you part for part for the number done in real life.

[Aaron Novak]

And there are URA and epoxy powders that are applied with great success on bare steel, aluminums, and mag parts.
Steel needs a etch to remove and foreign substances such as finger prints, or other oils, dirts and debris. then heated for a pre dry period prior to powder application and final bake.
Aluminums are also etched with a 6% chromic acid, rinsed and dried prior to coating, same as any application of any protective coating Liquid or power.
As I worked at NUW as a master engine mechanic I helped NUW become VOC compliant in applying proactive coatings.
Powder coating was our Saviour in complying with EPA rules for emissions on paint booths.
When you apply Powder coating properly, it is far superior to any paint system in existence today. and there are no powders that require temps to apply that will harm any metal parts in todays aircraft.

You may have privy to many lad results at Your facility but I'll match you part for part for the number done in real life.

Hey Tom,
Yes chromic acid conversions (i.e. iridite) are needed on aluminum, with any paint system. In the OEM world, just about all steel substrates have a phos conversion of some kind before the powder. Maybe in a moderate to light service condition just using a topcoat would be fine, but then why bother with powder? What liquid paint system are you comparing a urethane cured poly powder to?

[jwzumwalt]

I have been a pilot and A&P for over 40yrs in Alaska.
I have used epoxy paint (one and two parts), urethane, and powder coating.
For certified aircraft I used Dupont Imron for the first 20yrs but due to high prices,
I now use generic urethane.

My conclusion...

I have never found any zinc chromate that works very good; not even epoxy zinc chromate.
All of them quickly develop cracks and a zinc chromate surface can compromise a riveted joint.
The FAA prohibits paint between a rivet joint - even though everyone does it.

Powder coat is better than any other for durability.
So I powder coat instrument panels, engine parts, wheel rims, handles & knobs, etc.
And yes I have even used Harbor Freights cheapo system that works some what ok.
(It does tend to clump and be uneven)

Poly Urethane looks the best by far and the paint formulas are almost as good as epoxy.

So, I poly urethane when looks are important and powder coat when toughness is needed.
I never zinc chromate, I use alodine instead.

I moved to Southern Idaho 5yrs ago and now have to contend with desert heat. I have not
encountered any problems that make me think the warmer temperatures will require me
to change products or technique.

[Aaron Novak]

I have been a pilot and A&P for over 40yrs in Alaska.
I have used epoxy paint (one and two parts), urethane, and powder coating.
For certified aircraft I used Dupont Imron for the first 20yrs but due to high prices,
I now use generic urethane.

My conclusion...

I have never found any zinc chromate that works very good; not even epoxy zinc chromate.
All of them quickly develop cracks and a zinc chromate surface can compromise a riveted joint.
The FAA prohibits paint between a rivet joint - even though everyone does it.

Powder coat is better than any other for durability.
So I powder coat instrument panels, engine parts, wheel rims, handles & knobs, etc.
And yes I have even used Harbor Freights cheapo system that works some what ok.
(It does tend to clump and be uneven)

Poly Urethane looks the best by far and the paint formulas are almost as good as epoxy.

So, I poly urethane when looks are important and powder coat when toughness is needed.
I never zinc chromate, I use alodine instead.

I moved to Southern Idaho 5yrs ago and now have to contend with desert heat. I have not
encountered any problems that make me think the warmer temperatures will require me
to change products or technique.

You shouldnt be using a single component zinc chromate primer under a urethane anyway, thats a good way to invite filiform corrosion. Depending on the specific area, priming between components might be required, and certainly it is done in production applications. As for primers, epoxys are still top of the heap, the best ones (for aluminum) having strontium chromate as the sacrifical pigment. Without the pigment, the only mechanism the primer has is sealing, and once that is breached by a scratch, the sealing ability starts losing value. Certain pigments also form an ionic bond with the substrate that helps in edge sealing. The best materials I have ever found primer wise that are still available easily, is the Stitts EP line. ASTM salt spray, humidity cabinet, adhesion testing....all very impressive. PPG DP40 used to be quite good as well, sadly the LF version saw its performance drop drasticly.

[Matt Gonitzke]

The FAA prohibits paint between a rivet joint - even though everyone does it.

Can you cite a specific document or reg that states that? You sure are right about the 2nd part...everyone, including the OEMs, does it.