If the product you want to powder coat has a lot of debris (rust, laser scale, preexisting paint), then you will likely need a Blast Room. A blast room is an enclosure where you use compressed air to propel abrasive material against the surface of your parts. Depending on the situation, you would typically use either an appropriate blast media (grit) or steel shot to blast all the unwanted debris off your part until it has a clean metal surface that’s ready for powder coating. Blast rooms are especially useful for job shops that work with raw materials that aren’t pristine, such as plate steel or tube stock that has areas of oxidation or welding residue. (For more information on getting the right blast room, go here.)
If oils, solvents or chemical residue covers any part of your products’ surface, you’ll want to consider a Wash Station. A wash station is where you spray your parts with a detergent and/or chemical pretreatment agent, such as iron phosphate. Using hot water or steam to clean and then chemically prep parts is quite common. A wash station helps you increase powder adhesion and improve finish quality, even if the parts have already been blasted. Some wash stations require you to apply the chemistry manually using a spray wand. Other washers are automated and the parts travel through the cleaning, rinsing and prep stages on a conveyor.
In some operations, pretreatment requires the use of a Dry-Off Oven. This is commonly an appliance similar to a curing oven, but where the just-washed parts are heated in order to evaporate any water or chemistry still on them. This step can also help parts reach an optimum temperature for powder application.
Pretreatment equipment is incredibly useful for your operation and can make a big difference in the quality of your work, but an elaborate system isn’t always required for powder coating. While we can’t stress how important it is to have a clean surface before you apply powder, expensive pretreatment equipment isn’t mandatory for entry level coating operations where hands-on cleaning (such as with a tack rag and solvent) can be employed as needed.
Application: Powder Guns and Powder Spray Booths
Powder coating application is almost always done with a special Powder Spray Gun. In order for powder coating to work effectively, the powder must be electrostatically charged. The only way to apply this charge is with a spray gun designed exclusively for powder coating. Compressed air moves powder through the gun from a hopper or directly from the box the powder is stored in. The compressed air blows powder out of the gun as a tightly formed cloud. As the powder leaves the gun, it receives an electrostatic charge. Once charged, the powder cloud envelopes the part and the powder sticks to the surface of the grounded part (which is one of the reasons why powder coating equipment is so easy for new operators to use).
If you want to powder coat, you need a powder coating gun. There are many types of powder spray guns available on the market. We always recommend investing in a professional-grade powder gun, as they are more reliable and provide better results.
Once you have your powder gun, you’ll need to have a place to use it. Whenever you spray powder, some of the powder will end up on the floor and in the air instead of on your products. This leftover powder is referred to as overspray. Keeping this overspray out of your workspace is one of the functions of the Powder Spray Booth.
The powder spray booth is designed to keep the rest of your shop clean while providing a well-lit area for you to apply powder coating. All powder spray booths will have one or more exhaust fans. The exhaust will use filters to capture at least some of the overspray. If the exhaust works properly and the filters are maintained, the airflow in the booth should keep the overspray inside the enclosure and enable the painter to see what he’s doing. If your shop environment includes welding or blasting areas, filtered doors on the spray booth can keep airborne contaminants out of your powder coated finish.
Numerous booth configurations are available, and getting the ideal booth depends largely on what you’re coating, your floor space availability, and your workflow requirements. Powder spray booths can be open-faced or have doors on one end. They can also be tunnel style enclosures with the filtration built into the floor or wall(s). If you have space constraints, a Powder Spray Wall may help you get the airflow and filtration you need. A spray wall is just a large filtration system—essentially a spray booth without walls or a roof.
If you want to recycle your powder, you need to make sure your powder spray booth is built with a reclamation system. Usually this system will rely on pleated cartridge filters. These help you recover some of the overspray and reuse it. This can be very cost-effective if you are planning to use only one color and type of powder for your coating. The spent powder is trapped in the filters and then dislodged into a recovery bin for reuse. In more advanced systems, the powder is automatically reconditioned, mixed with virgin powder, and then returned to the supply hopper feeding the powder gun(s). If you are planning to reclaim a variety of colors, a set of removable filter modules is required. Unfortunately, the cost of buying multiple reclaim modules can add up quickly because you can only reclaim one color in each filter module.
No matter what type of booth you decide on, you’ll need a powder spray booth if you want to get quality results and maintain reasonable throughput from your coating operation. (For more information on what size powder spray booth you might need, click here.)
If you have stringent finish requirements, you may also need a Clean Room (also called an Environmental Room). This is usually a climate-controlled room built around the powder application area. The purpose of a clean room is to eliminate airborne contaminants and control the temperature and humidity during powder application to prevent any sort of contamination, clumping or consistency issues when applying the powder. Clean rooms are often recommended if your shop environment is particularly dirty or your products require an exact specification for adhesion or salt spray tolerance. (For more about requirements, click here.)
Curing: Powder Curing Ovens
After your product is powder coated, the final step is to place it inside a specially designed Powder Curing Oven. They usually operate between 325° and 450° Fahrenheit. Once the oven is up to temperature, the temperature stabilizes. The coated products are exposed to precisely heated air for a set period of time. Once the curing process is complete, the parts are removed and allowed to cool before being handled.
Some ovens use infrared emitters to heat the surface of the coated parts, but these types of electric powered or gas catalytic ovens can be costly to buy and expensive to maintain. More commonly, ovens rely on electric heating elements or a natural gas or LP-fueled heat system. These more conventional ovens typically rely on heated air moving over the parts for convection curing.
The time it takes to cure the powder varies greatly depending on the size, shape and thickness of the parts being coated. A small, light-gauge bracket can take as little as ten minutes to cure completely, while a 20’ section of heavy-walled pipe may take over an hour to cure properly.
If you want to powder coat at a professional level, the type of oven you choose is critical. Not only are brand-name powder curing ovens designed specifically to generate premium coating results, they are also highly efficient appliances in terms of fuel usage and energy costs. It’s likely that you’ll be using your oven several hours per week, so the cost of an inefficient design can quickly sap your profits.
Similar to powder spray booths, powder curing ovens come in multiple sizes and configurations. (For more information on what size powder coating oven you will need, click here.)
Professional Powder Coating Systems Layouts
There are two basic configurations for any powder coating line: batch or automated.
A Batch Powder Coating Line is usually a system where the parts are prepared, coated and cured in batches of multiple parts, with operators handling up to dozens or hundreds of parts at a time. The products are usually hung on metal rolling racks, which move with the parts throughout the coating process. (Remember: high-temperature or metal casters for your racks are very important!) With a batch line, parts are usually moved from stage to stage manually, and the term “batch coating system” is also commonly used to describe operations where large objects are coated individually after being moved by hand or with machinery.
An Automated Powder Coating Line uses basically the same appliances as a batch system, but connects many or all of the stages via a motorized conveyor that moves the parts through at a constant rate. The products are usually loaded onto the conveyor at a set location and move through each stage, where either manual operators or automated devices clean and prep the parts and apply powder to them. Once coated, the parts move through the curing oven and then cool as they travel along the conveyor to a point where they can be unloaded.
(For more information on whether a batch coating line or an automated coating line is right for your business, follow this link to learn more about the advantages and disadvantages of each system.)
Powder Coating Equipment From Reliant Finishing Systems
Hopefully this Beginner’s Guide to Powder Coating Equipment has answered your basic questions about what powder coating is, how it is done, and what you need to start your first powder coating line. If you would like to learn more, please give us a call at (888) 770-0021. Reliant Finishing Systems’ specialists can help! We’ll guide you through the process of setting up a powder coating shop or adding coating capabilities to your existing fab shop or manufacturing facility. Whether it’s your very first powder coating system or you’re upgrading to a complete automated line, you can trust Reliant to provide you with sound advice and affordable, high quality equipment.