Bulk coatings are an economical method of applying decorative and protective paint finishes to small parts, which lend themselves to one of these processes.
Japanning, Tumble Coating, Barrel Enameling
A coating method of applying paint to parts in bulk by dipping parts in a basket and then spinning the basket to remove excess paint. Baking between coats cures paint on the parts. A pretreatment with zinc phosphate is usually required before applying a painted coating. This method lends itself to many automotive small parts fasteners, springs, etc..
A coating method of applying paint to small parts in bulk by applying paint to parts in a tumbling barrel. Baking between coats cures paint on the parts. Several light coats are necessary to provide full coverage and prevent parts sticking together. This process coats only the outer portions of the part. Glossy smooth finishes are able to be met by this method.
Hot barrel coating
A coating method of applying paint to small parts in bulk by applying paint to parts in a tumbling barrel.
The parts are baked as the paint coating is applied. This process also coats many recessed areas of the parts as well as the outer portions. However, finishes are semi-gloss in appearance and not as smooth as the above method.