Powdercoating

comnoz · Dec 10, 2010

I have a powder coat setup also with an Inteck gun and an oven big enough to do frames. I have powder coat on a couple of my bike frames that I did many years ago but I have since wished they were painted. There is no question, powder coat is easier, cheaper and tougher than paint. I have not found that it was more chemical resistant however.
My problem is that I am never done with my bike, I always have to change something or weld a tab on someplace or move a bracket. With paint it is easy but I have not had nearly as good of luck at trying to blend in a powdercoat patch. Jim

DogT · Dec 11, 2010

I can't speak to 2-pack, but I know the spray on enamel I used on the frame and cradle did not hold up to the gas and oil that was always around. It finally looked like crap. I did try spraying some carb cleaner on the new powder coat and it didn't seem to harm it, but I didn't work on it very long, I didn't want to mess it up. Carb cleaner will take off just about any regular car paint with enough rubbing and it pretty much dissolves rattle can paint fast. Not as fast as MEK though.

Dave
69S

interstateOz · Dec 11, 2010

This is great as I'm in the process of trying too choice what to use powder or paint mmmmmm, I think I've made up my mind z few times then it changes again, I think both have there benefits, stil not sure yet so many different stories on each, I always thought a lot in paint was in the prep and primer but you'd done all that properly Josh?

Josh Cox · Dec 11, 2010

Well prepared on the BSA, but the paint did not last:

maximini · Dec 11, 2010

On the subject of powdercoat removal, I have had good luck stripping it using the POR stripper. If you put small parts in a plastic bag and seal it overnight the powdercoating comes off pretty completely.

rvich · Dec 11, 2010

Jeepers! This has nothing to do with this thread but the BSA is a pretty little bike!

Now on to the thread. I have a friend here in town that paints airplanes. Those cowlings take a beating from the prop blast and they are not strangers to av gas, oil and all sorts of abuse. I am going to call him and quiz him on this. I know he uses two part polyurethane paint.

Russ

PS-this friend is hard to reach and can smell a trap a mile away so this might take awhile...but I promise to report back with any info worth posting. I have a frame I need to do this winter so it is timely.

bwolfie · Dec 11, 2010

It depends on the aircraft type. It could be Alumgrip, Emron was replaced with a sherwin williams 2 part epoxy, the name escapes me right now, I'll have to call one of my Cessna buddys and find out what it was. It was very durable and chemical resistant all the way up to but not including Skydrol, nothing stands up to that.

bwolfie · Dec 11, 2010

http://www2.sherwin-williams.com/aerospace/jetglo.asp

Jet Glo

Josh Cox · Dec 12, 2010

rvich,

It looks even better with an engine and a seat.

Before:

After:

Carbonfibre · Dec 12, 2010

For bikes that are actually going to be used powder coating is far superior to paint, and contrary to popular belief chips can be touched up easily, it just takes a little longer than with paint. However some powder coaters will simply blast clean something like a frame, then apply the powder.This method will not result in a long lasting job, and any small defects in the surface will still show.

Ideally bike parts that need powder coating, should be blast cleaned if painted, or chemically dipped then blast cleaned if previously powder coated. Then they need to be heated in the powder oven in order to remove any trace of moisture, then primed and finally powder coated, ideally using epoxy powder, which is more durable than cheaper polyester based types.

grandpaul · Dec 12, 2010

Like with ANY finish application, SURFACE PREP is important in powdercoating.

Strip, visually inspect, repair cracks and any welds. Test fit everything, finish up last-minute bracket mods, etc.

Pre-heating is important to weep out any trapped petro products, then a final re-wipe and clean, THEN powder application.

I don't have any chips on over a dozen frames i've done, and none of my 20 or so clients have reported any chips.

Then again, my powdercoater is one of the best around.

GOOD prep + GOOD products + GOOD application = GOOD finish.

comnoz · Dec 14, 2010

Cheesy · Dec 14, 2010

comnoz said:

One thing that chart seems to be missing is UV stability, the epoxy powders are generally not UV stable. At work we have been through lots of 'fun' with getting our powder coating sorted. There is no way we would coat onto a blasted or cleaned steel, everything goes through a phosphate conversion and sealing process after decreasing and acid etching. It is then run through the oven to completely dry, then we use a zinc rich epoxy primer (powder) which is half baked followed by a polyester powder and then fully baked. The fun comes from having changed this process as we now coat zinc plated steel.....

Carbonfibre · Dec 15, 2010

UV resistant clear coat is generally used over epoxy powders without UV resistance especially on things like bike frames, where obviously the appearance is important. The person that does my bike parts is involved in refinishing alloy car wheels, where durability and long term resistance to corrosion are obviously just as important as cosmetic appearance.

comnoz · Dec 15, 2010

Cheesy,Couple questions from an amateur powder coater.
Have you guys had any problems with adhesion after the phosphate coat and does the zinc rich primer help that? And do you do a full bake before you use the clear topcoat? What prep do you use with aluminum? Jim

Cheesy · Dec 15, 2010

comnoz said:
Cheesy,Couple questions from an amateur powder coater.
Have you guys had any problems with adhesion after the phosphate coat and does the zinc rich primer help that? And do you do a full bake before you use the clear topcoat? What prep do you use with aluminum? Jim

CF, I didnt know about the clear UV coat over epoxy, makes sense though. Comnoz, the phosphate layer actually helped us with adhesion, this is a production process not a jobbing process so in some ways it is a bit easier, the critical aspect was removing all of the water from the surface as fast as possible after the hot rinse bath, even the smallest hint of rust is a problem down the line, production is in China so its relatively hot and humid, the uncoated steel forms rust fast. The zinc epoxy is to help corrosion resistance, I didnt notice any difference with regard to adhesion before or after we started using it. The epoxy is applied and goes into the oven for a 1/3rd of the total time (it is on a continuous chain), the polyester is applied straight from the oven then it goes back in (through), the epoxy is not fully baked when the polyester is applied, also the polyester isnt clear, it is either black or green. We dont do aluminium but I imagine it could be very problematic with the formation of the oxide layer, maybe anodised aluminium would be better to powder coat.... I dont know

Cheesy · Dec 15, 2010

comnoz said:
Cheesy,Couple questions from an amateur powder coater.
Have you guys had any problems with adhesion after the phosphate coat and does the zinc rich primer help that? And do you do a full bake before you use the clear topcoat? What prep do you use with aluminum? Jim

CF, I didnt know about the clear UV coat over epoxy, makes sense though. Comnoz, the phosphate layer actually helped us with adhesion, this is a production process not a jobbing process so in some ways it is a bit easier, the critical aspect was removing all of the water from the surface as fast as possible after the hot rinse bath, even the smallest hint of rust is a problem down the line, production is in China so its relatively hot and humid, the uncoated steel forms rust fast. The zinc epoxy is to help corrosion resistance, I didnt notice any difference with regard to adhesion before or after we started using it. The epoxy is applied and goes into the oven for a 1/3rd of the total time (it is on a continuous chain), the polyester is applied straight from the oven then it goes back in (through), the epoxy is not fully baked when the polyester is applied, also the polyester isnt clear, it is either black or green. We dont do aluminium but I imagine it could be very problematic with the formation of the oxide layer, maybe anodised aluminium would be better to powder coat.... I dont know

comnoz · Dec 15, 2010

Cheesy, I haven't tried phosphate under powdercoat although I have tried it under epoxy paint and had adhesion problems. Had been thinking of trying it with powder.
I have used clear polyester coat over epoxy powder but have not had good luck. It looked great at first but after a few weeks in the weather it got foggy looking. It may be due to the fact that it was on magnesium? I also tried clear polyester on polished magnesium and ended up with black spots [oxidation?] under the clear although it stuck very well. Jim

DogT · Dec 15, 2010

The guy in Front Royal that did my frame uses a phosphate dip before the powder coat. He told me it was something the DOD required on their equipment to reduce rust. I guess he does a lot of military parts. He said it prevents rust from traveling under the powder coat if it does get scratched.

Dave
69S

comnoz · Dec 15, 2010

DogT said:
The guy in Front Royal that did my frame uses a phosphate dip before the powder coat. He told me it was something the DOD required on their equipment to reduce rust. I guess he does a lot of military parts. He said it prevents rust from traveling under the powder coat if it does get scratched.

Dave
69S

I suspect it would help with rust. My phosphated sidecovers stayed rust free after the paint fell off. Jim

Powdercoating

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