Powder coating is a famous industrial dry paint. It has several advantages over conventional liquid paint viz High micron coating can be achieved without running, High corrosion resistance, Moisture Resistance, Acid Resistance properties are present in powder coating as compared to liquid paints. Apart from the technical point of view. Powder coating is very economical as compared with liquid paint. Powder coating can be used much time after dropping, but fluid paint dropping collection and its reuse is not accessible. After having such advantages, powder coating become failed because of lack of knowledge of the applicator. Here we are discussing the right way of powder coating process.
We have divided the powder coating process into four steps for better understanding.
Pretreatment Process (Surface Cleaning and Protection)
Surface Preparation before Powder Coating
Powder Coating Curing and Cooling
Powder Coating Testing
Pretreatment Process (Surface Cleaning and Protection): Surface cleaning or pretreatment of any substrate is every important for powder coating long life. Different metals follow different pretreatment processes. For example, the Aluminium Pretreatment process is different than Mild Steel Phosphating process. Necessary components of substrate cleaning are Oil removing, Rust or Oxide removing, Surface Coating and sealing. Mild steel coated with Zinc or combination of Zinc, Nickel and other noble metals. These metals give better corrosion protection on mild steel, But Aluminium protected with complex salts of trivalent & Hexavalent Chromium. Advance technology provides better aluminium protection with chrome-free compounds. They are also ROHS compliant. After pretreatment, the substrate must be free from any oil, rust and oxide layers.
Surface Preparation before Powder Coating: In this process substrate surface should be clean again but with air only. Sometimes a dry cloth can be use also. By following this process substrate would be free from dust and foreign particles. The presence of these foreign particles makes powder coating finish non-uniform. After cleaning with air or cloth substrate should be prepared to place inside an oven.
Powder coating and Cooling: Powder coating backed with the help of heat present inside the oven. The oven temperature can vary from 180 to 200 degree depends upon the powder you are using. You should ask your powder coating manufacturer for curing temperature. The powder coating should bake in a given heat for a given time duration. Time duration mentioned by the powder coating manufacturer. It usually varies from 10 to 15 minutes at a specific temperature. After successfully baking, it should be cool properly to become tight. Before cooling, it should not involve in any testing and assembly work.
Powder Coating Testing: it highly recommended to perform testing to measure powder coating success. There are many powder coating testing that industries are doing from primary to higher. But we are mentioning only essential and mandatory testing with their ASTM standards here. Gloss Test (ASTM D523), Impact Test (ASTM D2794), Salt Spray Test (ASTM D1117), Bend Test (ASTM D522).
Storage: After powder coating, the right placement is also crucial for powder coating long life. Substrate who treated with epoxy-polyester (Hybrid) powder coating should place in a closed store. It should not be present directly under sunlight. As epoxy-polyester is not capable for UV protection.