Powder Coating: How to Powder Coat

Powder coating is a new technology in which free-flowing, dry powder is used for coating metal surfaces such as decorative items, kitchen wares, bicycle parts or door handles. It is different from the traditional method of wet painting whereby a paint that consists of solid powder suspended in a liquid medium is used for surface finishing. The dry powder used in powder coating is either a thermoplastic polymer or a thermoset polymer. A cured surface after powder coating resembles a two-layered wet painting.

There are several advantages of powder coating in comparison to traditional wet painting. Since there are no volatile organic compounds in powder coating, it is an eco-friendly product. In case of over sprays, the powder can be recycled and used for another powder coating process. Powder coating results in a tougher surface finishing than wet paints. The cured surface is also resistant to rust, scratch, peeling and/or cracking. Speaking about the aesthetic value, powder coatings are available in a wide range of colors and texture.

Powder Coating: Working Process

In powder coating process, a uniform mixture of electrostatically charged powder particles containing plastic resins and pigments (that impart color) is sprayed on a pretreated metal surface. The metal surface applied with powder coat is then cured in an oven. The initial preparation or pre treatment is very important for a successful powder coating. If necessary, chemical treatment and abrasive blasting is done for successful powder coating. Pre treatment increases adhesion of the powder coat to the metal. In fact, most of the failures can be attributed to lack of proper preparation treatment.

The surface of the metal that is to be powder coated should be cleaned and rinsed thoroughly. Any oil, grease or oxides present can be removed by using weak alkali or appropriate detergent solutions. Further preparatory steps vary depending upon the type of the metal. In case you are powder coating aluminum, the surface should be pre-treated chemically to form a conversion coating by using phosphate or chromate solution. The conversion coating improves the coating of the powder to the metal and at the same time, reduces the chances of under film corrosion.

While purchasing the powder, ensure that it will suit to the metal surface that you are powder coating. For assuring, you can consult with a professional or the manufacturer. In order to convert dry powder into electrostatically charged particles, you can make use of a spray gun or compressed air sprayer. You can purchase any of these powder coating equipments from a reliable supplier. Fill the powder as per the directions and apply to a clean metal surface for trial. Once you are convenient in spraying an even thin layer, you can apply directly on the pretreated metal surface.

The next step after application of dry powder to the metal surface is curing under elevated temperature (350-400 degrees F). You can perform curing in ovens, if the size of the cured metal fits into the oven. Another option of curing is using infrared heat lamps. During the curing process, a thermoplastic powder remelts and cools down, while a thermosetting powder undergoes cross-linking chemical reaction. In either ways, the curing heat allows the powder coating to stick to the metal surface, thus resulting in a smooth finishing.

Some of the safety tips while applying the powder coating are use of safety gears like face mask, gloves and respirator. One should not inhale the powder during application as it can cause breathing problems. It is also to be noted that curing should be performed in ovens that are not used for food preparations.