The powder coating process was invented around 1945 by Daniel Gusting. With the latest in powder coating technology & equipment, powder coating is able to deliver a superior finish, consistently.
Powder coating is applied with specialized electrostatic equipment as a free-flowing & dry powder. A powder spray gun is used, which when triggered gives an electrostatic charge to the powder particles passing through it. Once the powder is applied, the coated parts are cured in an oven. This melts the powder and helps to crosslink the powder over the surface of the part & creates a tough, scratch-resistant & beautiful finish.
Powder coating also offers a wide range of specialty finishes such as texture, structure, crocodile, etc. that is hard to achieve through liquid coating methods.
Major applications of powder coating involve household appliances, aluminum extrusions, automobile parts, bicycle parts.
Brief illustration of powder manufacturing:
- The polymer granules are mixed with the hardener, pigments & other powder ingredients in an industrial mixer.
- The mixture is heated in an extruder.
- The extruded mixture is rolled flat, cooled and broken into small chips.
- The chips are milled & sieved to make a fine powder.
There are two major types of powder coating: Thermoplastic & Thermosetting powders:
- Thermoplastic Powders maintain their chemical composition as they cool & solidify, but they can re-melt after curing when exposed to sufficiently high heat. These powders are functional coatings that provide a variety of features including thick film coating, electrical insulation, and extreme mechanical and chemical resistance. Typical applications include: road marking powders, stadium seat frames, dishwasher baskets and pipelines.
- Thermosetting powders are used much more frequently in the world of powder coating; they cannot re-melt after undergoing an irreversible chemical bonding process. Thermosetting powders are extensively used in industrial powder coating applications, mainly used to create a hard film.
Thermosetting powders are derived from three major subtypes i.e. Pure Epoxy, Epoxy Polyester & Pure Polyester powders:
- Pure Epoxy powders are superior in terms of chemical resistance & corrosion protection & normally recommended for interior applications like industrial equipment, metal furniture, dielectric application, etc.
- Epoxy Polyester powders are superior in terms of mechanical properties, provide excellent flow & corrosion protection & are strongly recommended for interior applications like household appliances, light fittings, etc.
- Pure Polyester powders are superior in terms of outdoor durability & hence recommended for exterior application such as aluminum extrusions, doorframes, automotive components etc.
Major advantages of powder coating over liquid coating:
- Powder coating production lines produce less hazardous waste than conventional liquid paints.
- Zero VOC – there is no discharge of any volatile organic compound into the atmosphere means environmentally ecofriendly.
- Powder coating- A wide range of specialty effects is easily accomplished which would be impossible to achieve with other coating processes.
- Powder coatings can produce much thicker coatings than conventional liquid coating without run down or sagging.
Major disadvantages of powder coatings:
- The startup cost is very high – since heating is through an oven, the cost of running the oven tends to be very high. Hence Grand Polycoats is the best powder coating manufacturer in India that offers low bake powder technology for reduced energy consumption during application.
- Restriction on the size of objects/components being coated – only items that can fit inside an oven can be coated.
- Contamination problem – Due to the size of the particles, there are chances of contamination through external dust or powder of different origin.
- Thin layer coating system – In powder coating, it is difficult to achieve a thin layer of powder coating. The minimum DFT is 25-35 micron.
- Change over time – changing from one color to another or one product to another, the change over time is very high because cleaning is very tedious.
Frequently Asked Questions:
What are the industries where powder coating is useful?
Powder coating is widely used in the following industries:
- Home appliances
What are the steps involved in powder coating? (Part preparation or the pre-treatment, The powder application, Curing)
Powder coating involves three basic steps:
- Part preparation or the pre-treatment: This involves removing dirt, oils, greases, metal oxides, etc and is done using various chemicals.
- The powder application: The common method is to spray the powder using an electrostatic or corona gun. The gun gives off a negative charge, which is sprayed towards a grounded object by compressed air spraying, which is then accelerated towards the surface by a strong electric charge.
- Curing: When the thermosetting powder is exposed to a high temperature, it melts, flows, and then reacts to make a higher weight polymer in a network-like structure.
Does powder coating prevent rust?
Yes, powder coating is corrosion and rust-resistant. The coating provides a protective line of defense that helps prevent corrosion and rust.
How do you maintain powder coating?
You can maintain powder coating by avoiding harsh cleansers and pressure cleaning; protect exposed surfaces with wax and proper cleaning and maintenance.
Can aluminum be powder coated?
Yes, aluminum can be powder coated however the thin layer of aluminum oxide must be removed from the surface of aluminum before applying powder coating.