Powder Coating: what it is and how it works
24 August 2021
Powder coating is a well-established standard in industrial coating, guaranteeing the highest quality of treatment and a low environmental impact. Let’s take a closer look at this process, how it works and what benefits it can bring.
Powder coating has undergone considerable development in recent decades, both technologically and in application, making it one of the most widely used coating processes in the world. It is a process which can only be carried out on metal surfaces which are coated with synthetic resin based powder coatings (such as epoxy powders) for both decorative and protective purposes. Let’s take a closer look at what this practice consists of, the elements that make it up and all the benefits associated with it.
Powder Coating Application: Electrostatic Spray Coating
There are four different techniques for applying powder coatings:
- electrostatic spray coating;
- fluid-bed coating;
- fluid-bed electrostatic coating;
- flame-spray coating.
The most common and well established of these is electrostatic spray coating, which is extremely flexible and versatile, using specially designed guns for both manual and automatic use.
The coating powder is contained in tanks, connected to the guns via hoses; here the powder is electrostatically charged and sprayed onto the item to be coated by compressed air.
For the paint particles to remain attached to the article to be coated, the electrostatic effect comes into play: these particles are subjected to a process of negative electric charge, while the article to be treated on the surface is positively charged. The resulting electric field causes the coating to stick to the article.
The powder-coated article is then placed in the curing oven where the coating polymerizes and deposits permanently on the substrate, covering it with a uniform film.
It is worth emphasising the role of the gun in this process: as well as electrostatically charging the powder, it directs the paint to the target, controlling the shape and density of the cloud that is created.
Powder coating plants generally consist of:
- conveyor belts, whose task is to advance the items to be processed;
- a washing and pre-treatment system for optimum preparation of the workpiece for subsequent powder deposition;
- manual and/or automatic application booths for coating powder deposition;
- a curing oven.
Benefits of Powder Coating
A number of advantages characterize this application method, which can be summarized as:
- powder that does not adhere to the substrate can be recovered and returned to the production cycle;
- possibility of adjusting the thickness of the film;
- excellent coverage of edges and corners of the items to be treated;
- low operating costs;
- the mechanical characteristics obtainable, such as hardness and elasticity, can be very high;
- no problems due to possible vertical dripping of the coating.
In the video below, the combination of manual and automatic application of white powder coat.
The end result, at the end of the drying and cooling phase, will be an aesthetically perfect finish that is resistant to cracking, chipping and discoloration.