Powder Processing

Have you ever wondered how cars get that smooth and even paint coat? It is certainly not achieved through a roller or a paint brush. Those would leave obvious marks and other imperfections. Instead, automobile manufacturers use powder processing to apply a layer of pigment with impressive results. Thick coats can be created without fear of sagging unlike with liquid paints. Solvents are unnecessary so Volatile Organic Compounds are not as much of a problem, making this a better colouring solution for the environment. Professional painters can generated impressive special effects. The whole process can also be completed faster compared to liquid coats. Below are the steps to be followed:

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Part Preparation


Before anything else, the surface to be coated will have to undergo pre-treatment to ensure a good bond between the material and the powder. Any trace of dirt, oil, grease, and other unwanted substances must be removed. Sometimes straightforward mechanical methods are sufficient. Others may require the use of chemicals. The object might undergo multiple stages of cleaning to ensure a pristine surface. It will depend on the impurities present and the level of quality expected for the finished product. For example, objects might be submerged in phosphates for cleaning or sandblasted for surface texturing.


Powder Application


Once the part surfaces are ready, the process can move on to the powder application itself. For metal objects, the use of an electrostatic gun is standard. The powder is charged in such a way as to stick to the surface due to basic magnetism. The metal will then be heated to the point where the powder melts into a film. This will eventually harden when cooled. Sometimes the material is pre-heated before the powder spray to achieve a more uniform coat. However, this can result in other issues. An alternative would be to heat the object and dip it into a bed filled with powder. The tiny granules will stick to the surface and melt on contact.


Curing


Covering the whole surface with the powder coating is not enough. The film should be given enough time to cool down and harden as this will result in a chemical change that is favourable for durability and longevity. Curing creates a tough polymer under ideal conditions. In most cases, the powders are subjected to 390 degrees Fahrenheit for as long as 10 minutes. The temperature and timing can be tweaked depending on the materials and other factors. Manufacturing plants may use convection ovens, laser light, or infrared ovens to achieve the desired outcome. Laser makes it possible to finish the process faster than traditional means.


Removal


Powder coats can last for years if cared for properly. For instance, car paints will only peel off if someone purposely or accidentally runs a sharp object across the surface. If the coat must be removed for whatever reason, then the appropriate chemical must be used. Organic solvents like thinners are great for liquid paints but not so much for powders. Acetone, benzyl alcohol, and methylene chloride are better for this task.