Powder coating is the process of applying a paint in the form of powder. Regular liquid type paints are pigments and binders suspended in solvents. Powder coating is solvent free so you are just using the dry pigments and binders. Once the powder is sprayed on your work piece, it must be baked from 350 to 400 degrees for about 10 minutes. When the powder is heated, it melts into a liquid, connects together, cures, and once cooled, is dried to a hard, beautiful finish.
You can powder coat almost any object that can withstand the cure temperature of the powder. It is the most common to powder coat metal, however, you can also powder coat plastic, wood, and glass, again as long it wont be damaged by the heat.
Generally, when powder coating metal, the powder is given a positive charge when it leaves the gun and it is attracted to a grounded work piece. Once the piece is fully and evenly coated, you carefully transfer it to an oven that can heat the powder to the specified temperature. The powder will melt, flow out, and then cure during this process. The usual specification for the piece is anywhere from 350 degrees F for 20 minutes to 400 degrees F for 10 minutes.
Powder Coating metal serves a couple of purposes. The functional purpose is that it provides a barrier between the metal and the oxygen around it protecting it from corrosion. When it comes to iron or steel, this is very important to prevent rust. Media blasting a part before powder coating will provide a profile for the powder to adhere tightly to the part, this helps reduce the spread of rust underneath the powder coating after it is scratched and keeps it centralized to just the scratched area.
The aesthetic purpose of powder coat is that you can choose from an almost unlimited amount of colors, textures, gloss-levels, etc. Powder coat colors can be applied in multiple coats to achieve even more unique finishes.
An example of a baked on finish most people can relate to is a washer/dryer finish or household oven. These surfaces are usually not painted and have a factory powder coat finish.