Powder coating is the process of applying a free-flowing, dry powder to metals (mainly), although modern technology allows for other materials such as carbon fibre, plastics and MDF to be powder coated by using methods which require less heat and time.
It has become extremely popular since its introduction in North America in the 1960s; today, more and more companies specify powder coating due to its durable and high-quality finish. Other benefits include improved efficiencies, lower environmental impact compared to other alternatives (powder coating does not use solvents), comes in an almost limitless range of colours and can be used for both functional and decorative purposes.
Today, powder coating is a widely used and highly popular method of metal finishing used all over the world. However, it was first introduced in Germany during the middle of the 20th century, primarily as a solution to the environmental concerns caused by liquid coating’s solvent contamination.
Up until several decades ago, almost all protective coatings used were solvent-based – when these solvents evaporate, Volatile Organic Compounds (VOCs) are released into the atmosphere. This results in a strong odour being formed and has a highly hazardous impact on the environment, contributing to air pollution and smog.
Processes now involved in powder coating began to be developed in the early 1940’s (around this time polymer powders were flame sprayed onto metals with this being a common method of coating at the time). Daniel Gustin developed an electrostatic coating for which he went on to file a US Patent (2538562) in 1945. Entering the 1950s, Scientist, Dr. Erwin Gemmer developed a fluidised bed process which he also applied for a US Patent (3063860) several years later.
The fluidised bed process was immensely popular during the late 50’s and early 60’s – during this time other approaches were being developed and tested. From around 1962, electrostatic application of powder became more commercialised – using electrostatic spray guns to spray the powder. This process gained a lot of traction, with the four main thermosetting resins which were formed between 1966 and 1973 being:
The global growth of powder coating became prominent in the early 1980s, particularly in North America and Japan – with this process continuing to evolve since.
Fundamentally, powder coating works by applying a coloured powder onto a surface using an electrostatically charged powder coating gun. The powder is sprayed on using compressed air, which passes over an electrode in the gun providing a positive charge, which allows the powder to stick to the surface of the metal – or in recent years, with new processes being formed, on other materials such as MDF.
All products should be cleaned and treated prior to powder coating to ensure the powder bonds to the material effectively.
The powder-coated part is then oven-baked at a temperature of between 160 – 200 degrees Celsius for an average of 10 – 20 minutes. Most conducting or thermally stable materials are suitable for powder coating and metals are particularly good due to their high electrical and thermal conductivity. Complex metal components can be powder coated evenly with the finished product, if done correctly, providing a high level of finish which can last up to 20 years.
There are many benefits of using powder coating for finishing, these benefits include:
Powder coating is more durable
Powder coating is a highly economical, long-lasting and durable finish available on virtually all metals. Surfaces which have been powder coated are highly resistant to chipping, fading, scratching and wearing with colours staying bright and vibrant for long periods of time.
Powder coating is more environmentally friendly than other finishes
Of the finishes available, powder coating is one of the more environmentally friendly finishes available, regarded as safe for usage and disposal. Containing no solvents, they generate little to no amount of volatile organic compounds (VOCs), like formaldehyde; with it being inert, does not create harmful fumes or contribute to air pollution.
Using powder in a controlled environment is less hazardous for operators
As previously mentioned, powder coating contains no solvents and is inert making it one of the less hazardous finishing methods; the risk of nose, throat and mouth irritation is, in controlled environments, far lower than with wet paints.
Powder reduces processing times
Powder coating typically realises improved processing times to other methods such as wet painting. As there are no solvents present, no flash-off period (waiting time to recoat or spray once the first coat has been applied) is required.
As the coating is applied electrostatically, the electromagnetic charge used results in almost no waste during the process. Also, as there is no flash-off period required or second coat to get the desired effect, this can provide both cost and time savings for the operator.
Wide range of colours
Colour ranges in powder coating include:
Through colour matching, there is an almost limitless variety of colours which can be chosen from. An example of a (RAL) colour chart can be seen below:
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