Custom Powder Coating and Sandblasting in Belfast, Maine

What is Powder Coating?

Powder coating is a type of dry coating, which is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin." The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as "white goods", aluminium extrusions, and automobile and motorcycle parts. The process provides a hard, durable, baked protection to any metal surface.

Advantages

There are several advantages of powder coating over conventional liquid coatings:

Powder coatings emit zero or near zero volatile organic compounds (VOC).
Powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging.
Powder coating overspray can be recycled and thus it is possible to achieve nearly 100% use of the coating.
Powder coating production lines produce less hazardous waste than conventional liquid coatings.
Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items.
A wide range of specialty effects is easily accomplished which would be impossible to achieve with other coating processes.

The Process

The powder coating process involves three basic steps:

Part Preparation Process & Equipment

Removal of oil, soil, lubrication greases, metal oxides, welding scales etc. 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 soil to be removed and the performance requirement of the finished product.

Powder Application Process

The powder coating is applied to metal objects by spraying the powder using an electrostatic gun, or Corona gun. The gun imparts a negative electric charge on the powder, which is then sprayed towards the object, which is grounded. The object is then heated, and the powder melts into a uniform film, and is then cooled to form a hard coating. We can also heat the metal first and spray the powder onto the hot substrate. Preheating can help to achieve a more uniform finish but can also create other problems, such as runs caused by excess powder.

Curing

When a thermoset powder is exposed to elevated temperature, it begins to melt, 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 degree of 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 200° C (390° F) in 10 minutes. The curing schedule could vary according to the manufacturer's specifications.