What is Powder Coating?
Powder coating is a process in which a coating is applied electrostatically to a surface as a free-floating, dry powder before it is heated in an oven to finalize the coating process. The powder can be made of any number of products: polyester, polyurethane, polyester-epoxy, straight epoxy, and acrylics. The final process provides a thick, hard finish that is tougher than conventional paints.
How do they make it?
Powder coating can be accomplished through one of two processes: thermosets and thermoplastics. Thermosetting involves additional chemicals which react to the powder during heating. Thermoplastics have no additional chemicals and instead just melt and flow into the final coating. Both processes of powder coating look quite similar except for this distinguishing feature. The thermoset or thermoplastic powder is created by taking the powder input and binding the items together, heating the mixture, rolling out the product, and then breaking the polymer product into chips which can be ground into a fine powder.
Each of the processes of powder coating typically after the powder is created by preparing the metal to be powder coated. The object is cleaned with particular attention to the removal of any debris and oil, which can inhibit the attachment of the dry powder. Next, the dry powder is applied electrostatically—a process by which the particles of the powder and the object are charged through a high voltage electrostatic surge. This electrostatic stage of powder coating greatly increases the efficiency and productivity of the coating process by nearly 95%. Less paint is wasted, and the metal object is fully coated.
The sprayed powder coating is then cured at temperatures as high as 400 degrees for ten minutes so that the finish can set onto the object. While setting, the powder melts and flows around the object. The heat not only melts the powder but binds the polymer into a heavier polymer that bonds in a tight network-like finish. The curing not only coats the sheet metal product, but it also binds the polymer into a tighter, heavier finish.
Powder Coating Benefits
There are numerous benefits to powder coating items. The end product is a thick, dense finish on metal products which are considerably more durable and longer lasting than conventional painting. Powder coating is also typically a one-coat finish, so the process is quite quick and simple. Powder coating can also include multiple custom finishing colours and textures as the powders which are sprayed onto the item can be manipulated. Powder coating is an environmentally safe finishing process because it produces few volatile organic compounds. Finally, powder coating creates the most even finished surfaces (horizontal and vertical surfaces) because the powder is sprayed and heated across without drips or application traces.
There are two significant drawbacks to the powder coating process. First, powder coating produces a thick finish to metal products. It can be quite difficult for powder coating to produce thin finishes, particularly because as the polymer is thinned, it tends to produce a bumpy texture similar to the peel of an orange. Second, smaller sheet metal jobs might prefer a less expensive or complex finishing process. Powder coating requires spray materials, electrostatic booth, and an oven—all items which can be costly and involved for smaller projects.
Wet paint is the traditional (although technologized) process of applying a liquid paint to a substrate or product for finishing. Most sheet metal fabrication processes will use a spray, pump, or pressurized vessel to deliver the wet paint evenly.
Predominantly a Primer paint is applied as a Ground coat. The process of applying the base coat wet paint is accomplished by thoroughly cleaning and priming the substrate before wet-blasting liquid paint to an even thickness of approximately 15-20 micrometres. The wet paint is applied until the product is evenly coated with the desired thickness of paint. Often Lacquers can be applied to bring depth to the colour and provide longer-term protection.
Plating is the process by which metal is deposited on a conductive surface. (Think of how jewellery can be gold-plated.) Plating can be used for many purposes: decoration, corrosion inhibition, improve durability, harden, reduce friction, or improve paint adhesion.
The process of plating can be quite complicated and depends on the desired metal for plating and sought effect. Typically an item is covered with the desired metal, and some combination of heat and pressure are applied to fuse them—although vapours, vacuums, and liquids can also be used as adequate substitutes to the heat or pressure of traditional plating processes.
The benefits of wet paint and plating are quite complimentary to powder coating. Firstly, wet paint is ideal for products which cannot be heated for powder coating because wet paint does not require an oven for finishing. Second, wet paint can produce a much more extensive range of colours than powder coating so more custom colour work could require spray painting and plating. For example, in a wet paint range, you can choose from a range of RAL, Pantone and British Standard. Third, wet paint and plating can produce a much thinner finish than powder coating. Products which demand a thin finish can benefit greatly from wet paint. Finally, wet paint is a much more economic finishing process, particularly for smaller jobs.
There are two drawbacks to wet paint and plating. First, wet painting is not as durable as powder coating. Wet paint can require maintenance and re-finishing later. Second, wet painting can require multiple coats to get an even, unmarred finish. Because wet paint begins with a liquid, the finish can be tricky to guarantee the perfect finish—which results in multiple finishing coats.
What is Best for Your Application?
Deciding a winner for powder coating versus wet paint for your products can be a difficult decision. Ultimately, you need to consider the needs of your company, your customers, and your product. Powder coating and wet painting/plating can both offer you a finish to your product, which will be both functional and appealing.