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Old 8th November 2011, 11:23 PM   #1
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Default Major arcing with new stator panels

After spraying about 16 panels this weekend with 2 thick coats of automotive clear coat I reluctantly performed an arc test on one of the panels. I was shocked to learn that these panels arced through the clear coat enamel like crazy...

My question is that could it be possible that the cleat coat is still drying and conducting. I has only been about 24hrs since the last coat and even though we used an accelerator, we did not bake it. Has anyone had a similar experience.

...Will it eventually become less conductive and stop arcing, i don't want to create carbon trail by continued testing.

Or, am I screwed and need to paint some sort of insulating paint such as Glyptol or something?

FYI, there is also 2 coats of Hylux on the panels already! (it was heat cured and also failed miserably).

Thanks,
Doc.
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Old 9th November 2011, 01:19 AM   #2
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How thick is the coating?

The coating need to be quite thick.

Most of the data I have found for pants and generally clear coats seems to be about 400 to 500 volts per mil sometimes a little more as they have been starting to be inculding this data in the info sheets due explosions at the gas pumps cuased from static discharge to the body of the car through the paint.

I just picked up a little sprayer gun my self and I will be researching paints again.

jer
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Old 9th November 2011, 01:36 AM   #3
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What's the voltage you were using?

Wachara C.
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Old 9th November 2011, 02:21 AM   #4
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nylon powdercoat would be the number one choice of material (Nylon 66) as it has about the lowest percentage of creep you are likely to find in a powdercoat (that was what ML used at one time I cannot say what right now) polyester would be an ok second choice for shear dielectric strength but good old enammel is probably well worth a try. Next time test first though I am sure you have already established that. Once you have punched a hole through your insulation you can pretty much kiss that stator goodbye as you now have a carbon track through the dielectric which may as well be a piece of copper at these voltages. Most powder coaters have absolutely zero experience coating for dielectric purposes. Just ask them, they most all are concerned with cosmetic or corrosion applications. Consistant uniform coating thickness is important. Guess that`s why I have for the most part gone the insulated wire route as it is tested and backed by the manufacturer. You are going to have to do the R&D and figure it out with your coater. I do know that ML spent about a year working with their coater (a major company) before they met all their criteria. There are people who can do this for you who have the knowledge and experience but it will cost, you can even purchase coated panels last time I looked. Try here. Best regards Moray James.

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Old 10th November 2011, 11:24 PM   #5
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I am beginning... very very early but I picked up some insulating sprayon brand paint for not too much that goes to 2500kv. All I can help with now.
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Old 11th November 2011, 12:12 AM   #6
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You should check with the paint manufacturer and check to see how it is with respect to creep. As I mentioned Nylon 66 is one of the best you will find. The voltage gradient the maker supplies is tested on a flat even surface with a consistant film thickness. Perf metal presents the challange of sharp edged holes from which the coating will creep back from leaving a thinner coating once set up. This is a project with challanges and you might do well to follow the lead of others who have had success otherwise you will be re inventing the wheele on your own. Good luck and keep us all postedd as to your results good and especially the bad ones so others can have the advantage of your experience. Best regards Moray James.
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Old 11th November 2011, 02:39 AM   #7
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I've had good results with automotive 2-part poly clear coat by "misting" on many coats, with ten minutes or so tack-up time between coats, to first build a foundation, then thickness, until I have at least 10 mils on each side of the panel (I measure it with a vernier caliper or micrometer). I then spray on another final coat (or two) "just wet", for cosmetics. Typically this process exceeds the sprayable pot life of the paint so I end up mixing a second batch of paint to complete the coating.

If the coats are sprayed on thick and wet, the paint will flow away from the sharp hole edges, and that's where it's needed the most. Better to spray it too dry than too wet. And I suspect you don't have enough coating thickness on those panels too. I recommend at least 10 mils on each face.

Even though I've had success with catalyzed polyurethane, the stuff is dangerous to inhale and expensive as hell-- I'm thinking if I build more panels in the future, I will try to find a local powder coater who's willing to do up a few test panels first. I think powder coating is probably cheaper too.

Last edited by CharlieM; 11th November 2011 at 02:49 AM.
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Old 11th November 2011, 05:26 AM   #8
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Regarding the wholes... I read in an article on electrostatic panels that you have to worry about applying too much paint to where it keeps the charge from crossing the holes?
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Old 11th November 2011, 07:30 AM   #9
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I would like to see that article !

jer
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Old 11th November 2011, 11:45 AM   #10
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Quote:
Originally Posted by joojoo1234 View Post
Regarding the wholes... I read in an article on electrostatic panels that you have to worry about applying too much paint to where it keeps the charge from crossing the holes?
I would like to see that article too.
I have not heard that, but what I have heard is that excess coating thickness can close up the holes to the point where it impedes the sound coming thru the holes; resulting in lower output.

The bad rap on spray coating perf stators is that you get too much coating where you don't need it and too little coating where you do need it. I would have to say that's indeed true, but if you're going to use perf stators, you need to coat them with the greatest care you can muster to mitigate arcing.

On one set of panels I that spray coated with polyurethane, to 12 mils thickness, the hole diameters had only decreased by about .006" (average); which means that coating thickness on the hole side walls was only 3 mils, and likely even less on the sharp edges.

This happens because it's not possible to hold the paint gun perpendicular to the side walls of the holes, so all you get there is whatever overspray happens float in there and attach. We don't really need much coating to insulate the hole sidewalls per-se, but we do need a good buildup on the sharp edges and the only way to get there is to apply the spray perpendicular to those edges, and not so wet that it flows away from the edges.

Knowing this, when I spray a set of panels, I "dry spray" the coats, holding the gun at a 45 degree down angle (to the panel face) on the first coat, then a 45 degrees up on the next coat, then 45 degrees left on the next, then 45 degrees right on the next... repeating that sequence until I get at least 10 mils on the panel, then spray the last coat "just wet", at 90 degrees (perpendicular), for cosmetics.

The biggest mistake is spraying too wet, which causes the liquid paint to pull away from the sharp hole edges. At best, you're never going to get a uniform coating, spraying a liquid onto perf metal. But with care and proper technique, you can get a coating that will work with moderate voltages.

Last edited by CharlieM; 11th November 2011 at 11:57 AM.
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