Powder coating is a dry painting process used for coating metals. The metal is thoroughly cleaned and etched before the powder is applied. There are two types of powder used, thermoplastic and thermosetting polymer, which are cured using heat. Different types of guns and equipment can be used in the process. The finished product is thicker than traditional painting methods and may require sanding or grinding for reassembly.
The powder coating process is a dry painting process which is mainly used for coating metals. There are several methods of applying powder coating. The most commonly used method is to spray electrostatically charged particles of pigment and resin onto an electrically grounded workpiece. Heat is used to melt the powder, causing it to flow, form a thin film and finally dry to a hard, scratch resistant shell.
As with any paint job, the most important step in the powder coating process is surface preparation. Before applying the powder coat, the metal surfaces are thoroughly cleaned to remove oils, dirt and grease. After the metal has been cleaned, it is typically rinsed and subjected to an acid bath to etch the surface. An etched or lightly textured surface helps ensure proper adhesion and even distribution during the powder coating process.
The next step in the process is applying the actual powder. The method of application varies depending on the type of powder used. The two main types of substrates used in the powder coating process are thermoplastic powder and thermosetting polymer. Both types of powder rely on heat curing, but they do it in different ways.
Thermoplastic powder is usually applied to a heated workpiece. The hot metal causes the powder to melt, flow, and then harden after cooling. The thermoplastic powder does not undergo any chemical transformation as it hardens. This means that the finished work can often be reheated to even out any fine or uneven spots in the finish.
The thermosetting polymer is applied to the work at room temperature, then polymerized when hot in the oven. The part is heated and held for a specified amount of time at temperatures of 320-410 degrees Fahrenheit (about 160-210 degrees Celsius). During that time, the polymer undergoes a chemical change known as “crosslinking.” Curing of the thermosetting polymer occurs in four steps, which include melting, flowing, forming a gel, and finally curing to hard shell.
For powder coating equipment, there are different types of guns that can be used in the powder coating process. They all generally achieve the same result in different ways. These powder coating tools are designed to fluidize the paint substrate and electrostatically charge the particles as they leave the gun. The main difference from one style of pistol to another is the method used to introduce the charge.
Some powder coating professionals also use equipment called a fluidized bed during the powder coating process. A basic fluidized bed system includes a tank to hold the powder, a means for introducing the charge, and a low pressure air supply. As air enters the tank, the charged powder is liquefied or suspended in the air column and often resembles a boiling liquid. The part is then dipped into the suspended powder and then cured. The fluid bed method allows the painter to apply a thicker coat in one application.
The powder coating process adds more thickness to the piece than traditional painting methods. This is especially important for items that need to be interlocked after powder coating. If the work piece is being taken apart for powder coating, it may require some sanding or grinding upon reassembly.
Protect your devices with Threat Protection by NordVPN
