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rppearso
05-31-2014, 12:11 AM
Does anyone know if there is a powder coat that is commercially available that cures at ultra low temps (less than 212 F). I am looking to powder coat my magnesium Cleveland 40-78B rims and I am very concerned about over temping the magnesium. The rims have to be walnut sand blasted but I don't want to deal with any more corrosion as a new set of rims is $2200 which will ground me for the rest of the year. I am not completely sure if 212 is te magic number either I will have to call Cleveland on Monday.

I could just dip them in the MIL-M-3171 oxsilan as the data sheet calls out but im pretty sure that's what was on there and it peeled off and my rims got quite a bit of corrosion so im not sure that is the answer.

1600vw
05-31-2014, 04:40 AM
If you do not find the answer here, try posting this question to this group......http://www.homebuiltairplanes.com/forums/forum.php

Sorry I could not be more help.

Tony

Blue Chips
05-31-2014, 08:16 AM
Curious rppearso,
What is it you are concerned about happening at 212 degrees?

Ken

1600vw
05-31-2014, 08:43 AM
Certain parts can not be powder coated for at the temps needed to melt the coating this changes the structure of the metal. Most parts I would not powder coat. Get out your copy of 43.13, it talks about this. If you do not have this book, get one.

Tony

Blue Chips
05-31-2014, 09:03 AM
I wasn't born yesterday Tony, powder coating of magnesium wheels is done frequently, done right is the key.
Still curious, what his concern is about 212 deg, must have gotten that odd figure from somewhere, doubtful it's explained in 43.13

Mike Switzer
05-31-2014, 09:40 AM
Take a look here. I haven't ever tried it but a few guys I know have used Eastwood products to powder coat parts on their show cars.

http://www.eastwood.com/paints/hotcoat-powder-coating/powder-coat-guns.html

(I know of at least one set of magnesium rims on a Pantera that were powdercoated (multicolor) using Eastwood products)

Tom Downey
06-01-2014, 05:23 AM
no worries, just do it with any powder you like..

https://www.google.com/#q=melting+point+magnesium

TedK
06-01-2014, 10:36 AM
Slightly off track, but I am going to put PlastiDip-Spray on my wheels. I was looking at it on one of the car car tv shows. Sprays on, peels off if you later change you mind. Don't even have to demount or mask the wheel. Just peel off any overspray. lots of colors.

https://www.dipyourcar.com/PlastiDip-Spray-cat/

Aaron Novak
06-01-2014, 10:40 PM
Powder does not perform as well as liquid for corrosion protection. You will need a good conversion coat, and epoxy primer if you expect it to last. Those two components are doing the bulk of the corrosion protection.

1600vw
06-02-2014, 04:43 AM
I wasn't born yesterday Tony, powder coating of magnesium wheels is done frequently, done right is the key.
Still curious, what his concern is about 212 deg, must have gotten that odd figure from somewhere, doubtful it's explained in 43.13

My comment was not just to you. But its good to know you believe this.

My comment was for the dude or dudette who does not know this. We do have those who read these post and take this stuff to heart. They might miss the magnesium part and believe they can powder coat all parts. I met one such person and this is why I stated what I did.

Tony

Tom Downey
06-02-2014, 06:30 PM
Powder does not perform as well as liquid for corrosion protection. You will need a good conversion coat, and epoxy primer if you expect it to last. Those two components are doing the bulk of the corrosion protection.
BS, come into the 21 century, all powder coatings are far superior to any paint. Cleaned properly the parts will be preserved for the rest of time. I restore antique aircraft and have never found a part that can't be powder coated. (except exhaust parts) that have a low melting point, are never heat treated any way so you have no worries.
I have even P/C white pot metal parts with no problems.

Tom Downey
06-02-2014, 06:41 PM
powder coated wheels. and a few other things

Tom Downey
06-02-2014, 06:47 PM
Here is a link,, read it.

http://www.ppg.com/coatings/truefinish/products/powders/Pages/default.aspx

falcon21
06-02-2014, 06:57 PM
Slightly off track, but I am going to put PlastiDip-Spray on my wheels. I was looking at it on one of the car car tv shows. Sprays on, peels off if you later change you mind. Don't even have to demount or mask the wheel. Just peel off any overspray. lots of colors.

https://www.dipyourcar.com/PlastiDip-Spray-cat/

I would mask the tires and anything that you might get overspray on. I used plastidip on the wheels on my car and didn't mask off the tires. I found that near the rim where I was concentrating the spray it would peel off easily but towards the outside of the tire where the spray was lighter it didn't want to peel off. Now to get it off I need to put a nice coat on the tires to peel it off. You can mask outside of the rim leaving about an inch of tire exposed just be sure that you coat the exposed section just like you would the rim and it will peel off just fine when you remove the tape.

Aaron Novak
06-02-2014, 10:50 PM
BS, come into the 21 century, all powder coatings are far superior to any paint. Cleaned properly the parts will be preserved for the rest of time. I restore antique aircraft and have never found a part that can't be powder coated. (except exhaust parts) that have a low melting point, are never heat treated any way so you have no worries.
I have even P/C white pot metal parts with no problems.

Tom,
We have a full corrosion test lab, along with environmental test facilities around the US. Two PPG reps on site and do more powder coating in a day than most do in a year. I think I am current on the subject. If you wish, I can put you in contact with our chief coatings and corrosion engineer, who is a coatings consultant for the USN, and considered top of his field.

But since you like the internet....
http://www.magnesium.com/w3/data-bank/index.php?mgw=182

If it were me I would chromate and epoxy prime under the powder.

Tom Downey
06-03-2014, 05:44 AM
"" If it were me I would chromate and epoxy prime under the powder. ""

You can not.

Aaron Novak
06-03-2014, 06:22 AM
"" If it were me I would chromate and epoxy prime under the powder. ""

You can not.

Tom,
Yes, you can. It is done every day in production of OEM auto and marine parts. Steel parts commonly get a phosphate conversion, some form of epoxy primer (Liquid or EDP preferred), and powder topcoat. Aluminum and mag get a chromate conversion ( or other ), epoxy prime (preferably with strontium chromate i.e. stitts), and powder topcoat. The only times I have not seen a primer used, is in those DIY kits sold by eastwood, PBTP and such. They market and sell it without understanding the process, and do a great deal of disservice to the customers. The biggest pitfall of using powder incorrectly is how to remove it when it fails.

Aaron Novak
06-03-2014, 11:30 AM
Tom,
Yes, you can. It is done every day in production of OEM auto and marine parts. Steel parts commonly get a phosphate conversion, some form of epoxy primer (Liquid or EDP preferred), and powder topcoat. Aluminum and mag get a chromate conversion ( or other ), epoxy prime (preferably with strontium chromate i.e. stitts), and powder topcoat. The only times I have not seen a primer used, is in those DIY kits sold by eastwood, PBTP and such. They market and sell it without understanding the process, and do a great deal of disservice to the customers. The biggest pitfall of using powder incorrectly is how to remove it when it fails.

Actually I have seen powder only (meaning no primer etc) in non critical applications for decorative purposes, and myself have done it, however I consider aircraft parts to be critical applications, and do all I can to prevent corrosion.

Tom Downey
06-04-2014, 05:06 AM
For those still following this thread, paint a piece of steel with epoxy paint, then heat to 400 degrees, see what happens.

Aaron Novak
06-04-2014, 07:34 AM
For those still following this thread, paint a piece of steel with epoxy paint, then heat to 400 degrees, see what happens.

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. This is to be sure all solvents are released, preventing pinholes in the powder topcoat. As an option there are epoxy powdered primers that do almost as well as liquid epoxy (conventional or EDP), typically they are only run through a partial cure before being topcoated with a "poly" powder and then fully baked. In either case, a pretreatment of the mag is still a must.

Back in the 90's it was thought that powder paint would replace all the steps of the standard liquid paint system by being able to be applied directly to a clean substrate. This was found to not be the case. The impermeability of the TGIC powder paint actually made some forms of corrosion worse by trapping moisture under the surface, causing the galvanic corrosion cells to run rampant.

http://www.mercurymarine.com/media/mercury/pdfs/engines/outboards/advantage/8M0065840_CrrsnPrtctnBro-212LR.pdf

Tom Downey
06-04-2014, 08:21 PM
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
06-05-2014, 12:04 AM
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
08-28-2014, 09:18 PM
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
08-28-2014, 10:30 PM
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
08-29-2014, 04:29 AM
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.