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Powder coating is the application of a dry paint in the form of a powder onto a surface using the principle of electrostatic charging. Powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. After the application process the paint is cured under heat to allow it to flow and form a “skin”.
Before applying the finish, the chosen part must either chemically or mechanically cleaned, removing dirt, oils, old, finishes, and oxidation. Poor surface preparation results in powder coating problems, which is because of impurities and poor adhesion between the powder and the metal base.
Rainbow uses several cleaning methods for powder coat prep depending on size, material, cleanliness, etc. Because we do so many metal finishes in house we have cleaning methods for any metal at our disposal. Our main method utilizes a phosphate coating followed by a quick dry in the oven for Ferrous or Iron based items or an etching, degreasing combination with chromate conversion process for aluminum.
In the application process, the polymer paint powder is applied from an air-powered gun. As the powder leaves the gun, it is given a positive electric charge while the part is grounded, giving it a negative charge. The powder flows and “sticks” to the grounded surface due to the attraction of the dissimilar charges. Where regular paint will over spray, causing waste and mess, powder wants to attach itself to the grounded part as much as it can. This causes a significant reduction in wastage.
After the part is fully coated, it is placed in an oven at 200-210 C .
Time and temperature vary according to types of polymers and part mass.
We carry a variety of powders for materials in a variety of applications. If we don’t have it in stock, we’ll track it down for you. If you don’t know what kind of powder would be best to use for your project, we can help find it for you.