The Powder Coating Process
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Powder coating can generally be broken down into three steps. 1. Part Preparation 2. Powder Application 3. Curing ****************** 1. Part Preparation: Sandblasting / Media Blasting The first sandblasting process was patented in the US in 1870. Sandblasting is a surface treatment using compressed air to propel abrasive media at a surface to produce a roughened surface or to remove mill scale, corrosion (rust), coatings (paint), heat treatment discoloration, weld spatter or other physical defects. Sand used to be the most commonly used material, but since the lung disease silicosis is caused by extended inhalation of the dust created by sand, other materials are now used in its place. Blasting is carefully controlled, using an alternate air supply, protective wear, and proper ventilation. The blasting process primes a surface for powder coating. Blasting is used on products that have a surface that would hinder adhesion of powder such as old finish, oxides, rust or manufacturing product that remain on the metal. When painting, one doesn't want to trap dust, dirt, or bubbles in a previous layer of paint, or other imperfections under the new layer. While blasting the surface at a high speed, imperfections are knocked loose and can then be easily washed off, creating a surface upon which the powder will adhere. We do our blasting with a medium abrasive media and have the capability of regulating pressure for different applications. Pre-treatment The key to a long lasting powder coat finish is in the preparation of the metal. Our shop takes great care in the preparation process. Pretreatment during the cleaning process, involves degrease, alkaline rinse and a phosphate wash, in addition to high pressure, high temperature wands that spray the solutions at 180F. That takes care of the oils and dirt. For the out-gassing, we usually pre heat the parts. The idea is to heat the items to a temp HIGHER than what the cure temp is before we coat them. That way, while we apply the powder and send them in to cure, they are actually cooling from around 425F to 390F, which will have the effect of pulling the coating in to the parts rather than have the gasses pushing out. Areas not to be powder coated Frequently the parts we coat have critical surfaces that must not be coated. We use high temperature tape (to mask off the area and allow finishing up to it) or silicone plugs (to plug plain and threaded holes), that are designed for powder coating. We custom design our own masking and plugs when needed to insure optimal finish. We also use masking tape when we do two tone finishes. 2. Powder Application: 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 to the powder, which is then sprayed towards the grounded object by mechanical or compressed air spraying and then accelerated toward the workpiece by the powerful electrostatic charge. 3. Curing: After the parts are coated with powder, it is crucial to bake them within a proper temperature range. This cure process requires a certain temperature for a certain length of time in order to reach full cure and establish the full film. The powders cure at 300°F to 400°F for 10 - 15 minutes at part temperature. The heat in the oven will cause the powder to melt and form a plastic sheet around the part. At this point, the powder bonds not only to itself but to the part as well. We ensure that every part receives the proper attention. This process gives the powder coat its increased durability and professional finish. The temperature of our oven is carefully tested and regulated to keep the bonding process at its maximum level of efficiency. The result is a beautiful re-finished part that is durable and ready for immediate use. Batch Powder Coating Processing Batch powder coating systems offer a number of strategic advantages, including the opportunity to run a variety of part sizes, the ability to achieve a fast setup for color changes, the ability to respond quickly to customer needs, and the capacity to handle large or heavy parts. Batch systems allow for the flexibility of a manual coating operation and extra attention to detail. Our walk-in systems can handle complex- shaped parts, very long parts, parts requiring low or high film builds, and very large or small parts. Oven Size: 22.5’ Long X 8’ High X 8’ Wide 14' Long X 8’ High X 8’ Wide |