Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat. (Approximately 400 degrees, depending on the powder manufacture.) Powder is used in place of traditional paint to create a hard finish that is tougher than conventional paint. Powder colors can be seen at prismaticpowders.com.
The powder coating process involves three steps:
- Part preparation or the pre-treatment
- The powder application
Prep involves removal of oil, dirt, lubrication greases, metal oxides, welding scale old paint, old powder coating or rust. This step is essential prior to the powder coating process. It can be done by a variety of chemical and mechanical methods. The selection of the method depends on the size and the material of the part to be powder coated, the type of impurities to be removed and the performance requirement of the finished product. At Emerald Coast Coatings, we media blast all steel and on new aluminum we chemically treat as required.
The most common way of applying the powder coating to metal objects is to spray the powder using an electrostatic gun. The gun imparts a negative charge to the powder, which is then sprayed towards the grounded object by compressed air and then accelerated toward the workpiece by the powerful electrostatic charge. After the entire project is covered, it is cured.
When a thermosetting powder is exposed to elevated temperature, it begins to melt or what we like to refer to as flows out, and then chemically reacts to form a higher molecular weight polymer in a network-like structure. This cure process, called crosslinking, requires a certain temperature for a certain length of time in order to reach full cure and establish the full film properties for which the material was designed. Normally the powders cure at 390° F for 10 minutes. The curing schedule could vary according to the manufacturer’s specifications. We make sure all parts reach required temp and cure for required time specification to ensure a quality job.