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In a comment to my question regarding white powder which had formed on aluminum parts after cleaning them with heavy duty degreaser, @Paulster2 mentioned a process called powder coating which would prevent future corrosion and make future cleaning easier.

What is this powder coating, and how may it be done?

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Simply speaking, a colored plastic powder is applied to the parts with an airgun. The parts are then heated until the powder melts and forms a smooth (up to high glossy) surface. Once cooled down, you have a nice, hard coating.

The powder may also be a thermosetting polymer, i.e. it does not only melt above a certain temperature, but also cures. When heating the parts again, the coating doesn't melt any more and stays solid.

The powder is electrically charged by the airgun, and a high voltage is applied between airgun and parts. This makes most of the powder fly to the parts and stick at their surface, and only little waste on the floor. Even the wasted powder can be recycled.

Only metal can be coated by powder coating, and the preparation includes careful removal of any corrosion by sand blasting. For aluminum / alloy, glass bead blasting is better since sand give a too rough surface. Sometimes, chemical treatment is used to increase corrosion protection and / or adhesion of the coating.

The benefit of powder coating is that it's really fast and cheap, needs just one layer (no primer, filler, color, finish), builds rather thick layers (>100µm), can fill small scratchs, withstands most chemicals and is mechanically more resistant than most other colors.

Since powder coating is really, really cheap, while the equipment is expensive, I would recommend to find a company to do this for you.

For example, I got both alloy rims of my scooter coated for 10-20€, when I brought them blasted, which cost another 10-20€.

By the way, wikipedia also has a large article about powder coating!

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    Great answer. +1! One step which is performed, but not mentioned, is called out gassing. This basically is heating the part up to temperature prior to actually applying the powder after which the part is allowed to cool. This ensures all oil and such which is in the pores of the metal are brought out. Without this step it will screw up the coating process. Also, every powder temp may be different, depending on the type of powder, but the ones I've seen are usually baked ~400°F (~204°C) until the powder flows, which takes about 20 minutes. – Pᴀᴜʟsᴛᴇʀ2 May 8 '16 at 17:47
  • What kind of shop would do stuff like this? – Robert S. Barnes May 8 '16 at 17:53
  • @RobertS.Barnes: There are typically companies specialized to powder coating in general. They have customers from the automotive industry, but are themselves not necessarily related to the automotive field. Also, most car shops won't powder coat on their own, but send parts to that companies. So, just study your yellow pages for "powder coating" and "(glass beard) blasting". That's how I did it. – sweber May 8 '16 at 18:04
  • @Pᴀᴜʟsᴛᴇʀ2: Is it really done to remove oil? This temperature will not do much to toil. I guess it is done to evaporate any water / solvents used in the steps before. – sweber May 9 '16 at 7:15
  • @sweber - It's how it was explained to me by the guy who did the oil pan and intake on my Z28 a few years back. It is an absolutely needed step to ensure proper adhesion of the coating during baking. Maybe he didn't convey it very well to me, but that's what he explained. This article describes the process and the reasoning behind outgassing. – Pᴀᴜʟsᴛᴇʀ2 May 9 '16 at 15:15

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