Powder coating ?

[gldavison]

I'm about to dive into powder coating, and have a couple questions.

!: While moving a part from the spray booth to the oven, is it likely some powder will fall off the part? Which bring me to question

2: Just how long will that powder cling to a part?

[Doc]

I dove in a little over a year ago.
And I do like it. I do small parts and haven't had any trouble with much of the powder falling off. Seems like it sticks pretty good. I rigged up a toaster oven to be able to hang my parts in it.

Here is the one I purchased for my model engine parts. POWDER COAT GUN

[Robert Hornby]

I was in the powder coating equipment industry for a while, and if you are careful with the job and do not bump it all the powder will stay on for quite a long time, normally the job is put straight into the oven. Often production items are on an overhead conveyor with out problems of loosing powder.
Robert

[Rustkolector]

Gary,
The spray gun that sprays the powder finish to your parts electrostatically charges the powder particles so that they cling to the part. How long it will hold on is a good question, but I doubt it is a problem. You would normally bake the parts immediately after coating. The parts need to be grit blasted to provide an etched surface to assure a good bond. Then you bake the parts at 375-400F for half hour or so. The latter fact is one of the reasons why I don't use powder coat. The baking temperature is dangerously close to the melting point of 4% silver solder which I use frequently for my models. Thermostats are not always close regulating devices.

I stopped using paint on my models many years ago due to high build up thickness, chipping around fasteners, and poor adhesion to brass and aluminum. I started using a baked on coating called Gun Kote http://www.kgcoatings.com/. It is a industrial coating and Mil spec finish for extreme use weapons. It goes on very thin and has never interfered with close fitting engine parts. It is impervious to any solvent I have ever used including brake cleaner. It won't chip under bolt and nuts even after repeated assembly and disassembly cycles. It adheres very well to brass and all other metals I use. And, it bakes on a 300-325F which is at lesst 100 degrees F less than the melting point of silver solder which I consider a very safe margin even for cheap thermostats. I use an inexpensive air brush to apply the coating at low pressure. So far, all of my painted parts have been baked in an inexpensive toaster oven. Part preparation is similar to powder coating with #120 Alox grit blast. As with powder coat, grit blasting is about the only way to remove it once baked. Product cost is about the same as powder coating, but the application equipment is much less expensive.

Jeff

[gldavison]

Hi Jeff

I remember you telling me about Gun kote.
What got me started on the powder coating project was this fellow in Germany who is powder coating his Snow engine parts. I was telling a friend here in town about this and he says, well I've got a brand new powder coating gun I'll give you. So he brings the thing over and it's a brand new Craftsman,(http://www.ebay.com/itm/NEW-Craftsman-Electric-Powder-Coat-car-boat-paint-Spray-Gun-17288-Metal-Finisher-/251750611817?pt=LH_DefaultDomain_0&hash=item3a9d817b69), never been used. I quickly found out why. The knob that locks the powder canister on the gun was broken and you could not get it off. No problem I just took it apart and repaired the lock and put it back together. So then I started investigating the powder coating and  bought some powder. Then I started checking out my toaster oven and found out I needed to fix that right away. The thermostat on the toaster oven is very inaccurate.
Using a voltmeter I have with a temperature probe, I set the thermostat at 300 and it promptly went to 425°  before it shut off and then returned clear down to 210 before it kicked back on. From then on, it was 100 to 120 degree between cycles. I'm in the process of installing a temperature controller(http://www.amazon.com/gp/product/B007MMOEWY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1), I found on the internet. The thermocouple probe for my voltmeter, (k-type),is one of several listed for this controller. It use a solid state relay to control power to the oven.  A preliminary test showed this thing is very accurate.
I set it for 200 degrees and after about 4 cycles it was maintaining this temperature within plus or minus 5 degrees.  Maybe I should say, it's maintaining the numbers I put in the controller. How accurate my probe is anybody's guess. Should be in the ballpark though, and a lot better than the internal thermostat.


Robert

I will be  transferring the parts to oven immediately after coating. Was just curious about the time factor. Thanks.

Doc

I looked at that HF gun. I like the fact that each color is in a jar the screws on the gun. I'm thinking changing color in this Craftsman cup might be a big pain in the ass.

[sshire]

Unlike much of HF offerings, I've had great success with their powder coating gun. The powders in their separate containers make changing color very easy.  I hang the parts with stainless steel wire hooks for coating and then hang the hooks from the rack in the oven. I'm quite sure my temps are varying over a wide range, but I've never had a failure. If the oven is hot enough to melt and fuse the powder, it works.
The PID controller is a great idea, I've got a few around that have been used on various espresso machines. I'm going to resurrect one based on your suggestion.
The Gun Kote sounds interesting. Another product to try. The fun never ends.

[ShopShoe]

Stan and gldavison,

This discussion got me thinking that larger parts made of material that holds heat better would not be needing as accurate temperature control as the material would lose and gain heat more slowly than smaller, less-heat-holding materials would. I believe that this is called thermal inertia.

Just thinking about it.

--ShopShoe