Since its development, powder coatings have been rapidly popularized for their advantages of energy-saving, environmental protection, and high efficiency. Powder coatings have been widely used in household appliances, instrumentation, transportation facilities, lighting, steel structures, hardware tools, metal furniture, aluminum profiles, construction steel, various vehicles and furniture, coil steel. In the coating process of powder coatings, there are often defective products that need to be reworked. Many reusable powder coated products need to be refurbished. Most of them need to be removed and cleaned before recoating. At present, there are three methods for removing powder coatings, such as mechanical grinding, high-temperature baking, and chemical solvents soaking.
Remove Powder Coating │ Grinding
It is usually done by hand grinding, mechanical grinding and sandblasting for the method of mechanically rubbing the coating to remove. Powder coating applicators often use manual or mechanical grinding. Generally, the surfaces are sanded and removed by sandpaper when local areas are such as granules, depressions, foaming, etc. The removal effect is that the remaining coating film should be intact and adhered, and no rust and air bubbles under the coating film. It can be rubbed with different sizes of sandpaper. The operation method is simple and easy, but the labor intensity is high, and the efficiency is low. Generally, it is only used for a minimal amount of returning workpiece. Since the powder coating thickness is usually 60-90um, the physical and mechanical properties are high, which makes it difficult to altogether remove the surface coating of the workpiece after blasting. Therefore, the grinding method is mainly used to deal with the defective parts of the products such as particles, pits, bubbles, and scratches, and the ground workpiece is put on the production line and then sprayed again as a whole.
Remove Powder Coating │ High-temperature Baking
The high-temperature baking method includes open flame burning, high-temperature baking, and high-temperature aging + sandblasting, etc.
I use an open flame to burn the powder-coated parts, let the surface coating burn to the ash and then clean the surface of the component mechanically or manually. Many powder coating applicators use this method to deal with powder-coated hangers and small defective powder coated products, which are low in cost, simple and easy to use and are used commonly now. However, the combustion of the powder coating layer releases a large amount of gas that pollutes the environment. The burning of open flames also damages the physical properties of the metal components being treated. Therefore, open flame burning is not worth promoting.
High-temperature baking, that is, using a device to bake the surface coating of the powder-coated part with heated high-temperature air, so that it is aged at a high temperature and coked until it is ash into ash. The drawback of this method is that it must carry out equipment investment, and the size of the processing parts should not be too large.
High-temperature aging + sandblasting method. Firstly use the coating baking facility for baking the powder coated products to be treated at high temperature to make the coating aging or coking, and then sandblasting, the aging coating can be bright. The shortcoming of this method is that batch processing is required, and the treatment time is long, and the coating coking still produces a small number of toxic substances and is discharged into the environment.
Remove Powder Coating │ Chemical Solvent Pickling
It is divided into three types: alkaline pickling, acid pickling, and organic solvent soaking.
The powder coating is removed by a high concentration solution and high-temperature immersion for both alkaline pickling and acid pickling. These two methods are rapid and straightforward, but they not only limit the material, but also has cumbersome post-processing, and requires a large amount of washing water.
The deplasticizer mainly utilizes the penetration and swelling action of the solvent on the coating to soften the layer, foam, and eventually fall off. The surface of the workpiece after deplasticization is mainly the volatile residue of the solvent and a small number of corrosion products. It can be repainted after being cleaned by degreasing, and the surface can be cleaned by sandpaper. Powder coating applicators rarely use deplasticizers because of the many problems in procurement and transportation, and there are significant contamination problems during the use of deplasticizers.
Whether it is a powder coating manufacturer or a powder coating applicator, it will encounter the problem of stripping. How to choose the correct powder coating removal method will be very important. The recommendations should consider the following factors:
- The final cleaning effect, because the purpose of the removal is to obtain excellent film properties again.
- Powder coating removal speed is essential data, which determines the output rate.
- The cost of powder coating removal must be disregarded and should include investment in coating removal equipment and operating costs.
- Operating environment and labor intensity.
- Environmental or not.
Mechanical grinding, high-temperature baking, and chemical solvent soaking methods have their characteristics and deficiencies and can be selected according to the actual situation and requirements.
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