Powder coating provides a durable, lasting alternative to liquid paint. Its application process requires careful pretreatment and an electrostatic charge to adhere the pigmented coating onto the surface. With powder coating, surfaces have protection and visual enhancement, making this finish an ideal option for many industries.
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Powder coating is a dry powder applied to a charged surface, creating a thicker coating in one application more than a single coat of paint. An electrostatic charge holds the coating onto the surface, which remains in place after curing the object. Due to the intensive process required to prepare and coat the surface, powder coating is a practical approach for large-volume orders.
Powder coatings consist of several ingredients. A polymer resin creates the finish’s core. Additional elements in the coating include ingredients to help with curing, pigments to add color, and flow modifiers. These parts work together to create a colored, protective surface that performs well in many environments after curing.
Generally, there are two types of powder coating – thermoplastic and thermoset. These differ in their curing methods and properties.
First, thermoplastic is a coating that melts and flows when heated, yet maintains the same chemical composition once it solidifies. It offers better resistance to impacts in the finished product. Plus, it does not need a curing cycle. Instead, the coating requires time and high temperatures to melt, flow evenly over the surface. Because it does not undergo curing, it can soften and remelt when subjected to high temperatures. Thermoplastic powder application requires a much thicker millage than thermoset powder coatings and often does not offer as nice of a visual appearance as compared to a thermoset.
Secondly, thermoset powder coatings go through an irreversible chemical change during curing to create a long-lasting, hardened coating. While thermoset coatings still melt and flow when heated, their structure chemically cross-links to form a different chemical composition than the base resin. Because the changes after curing are permanent, this type of coating will not remelt under intense temperatures. Plus, it provides better scratch resistance compared to thermoplastics. Thermoset powder coatings develop thinner films, which can be more visually appealing than some thermoplastic. However, when applied in thick layers, it can become brittle or crack.
Because these types of powder coatings have different properties, the best choice depends on the finished product’s application and use.
Powder coating has many applications in automotive, aerospace, manufacturing, and other industries that require durable finishes for products. Thermoplastic coatings can be beneficial in functional settings, such as dishwasher racks, playground furniture, light poles, and pipes. Meanwhile, thermoset powder coatings are useful in a wide array of applications, from lawn and garden products such as mowers or shovels to furniture, fencing, building facades, and many, many more.
Powder coating uses an electrostatic process and curing to adhere the powder to the surface. Because the parts must undergo high temperatures to set the coating, the substrate must also be heat-resistant. However, most products coated with this finish are metal and easily hold up throughout the process.
Surfaces that use electrostatic applications have the metal components grounded. While the powder itself is inert, it gains an electrostatic charge as the particles pass through the spray guns. The guns have an electrode fitting that adds an electrical charge to the powder particles. When sprayed onto the grounded surface, the particles stick. They become solidified into a dense coating during the curing process that melts and sets the finish.
Another less frequently used method is a curing fluidized bed. This method heats the part first. Next, the heated part submerges into a bed of powder coating. The heat melts the coating, which covers the surface evenly. This method works for thermoplastic coatings and non-metal materials.
The durable powder coating provides a thick surface over the part. It resists damage from impacts and scratches. Unlike paint, powder coating generally does not require touch-ups due to chipping or fading. It provides long-lasting color for applications in harsh environments.
The powder coating process includes several steps, each of which helps ensure the finish’s success, longevity, and durability.
Blasting is a step used to remove inorganic contaminants, like welding smut, rust, and laser scale, or for previously finished surfaces. The blasting process uses abrasives to take off paint or other finishes, rust, or corrosion. By ensuring the surface does not have contamination, the finishing company can ensure better powder coating adhesion.
The most critical step of the powder coating process is pretreatment. This step is so crucial that we use an eight-step pretreatment method. First, an alkaline cleaner takes off organic liquid and dust contaminants. This stage finishes with two thorough rinses to remove all surface debris and cleaning chemical.
Next, the part undergoes an iron phosphate application to prepare the surface for better powder coating adhesion, and improved corrosion resistance. Dual rinses get all traces of the iron phosphate from the part’s surface.
A reverse-osmosis water rinse removes any remaining solutions from the surface. Finally, a chrome-free zirconium sealer covers the surface. This layer dries in place and seals the surface, readying it for the following stages of powder coating.
A primer added to the surface before the powder coating application is optional. However, it can help the finish on aluminum or steel products last up to four times longer than non-primed surfaces. Therefore, consider priming aluminum or steel components intended for outdoor use.
Masking blocks off areas of the part that do not need powder coating. It protects these areas from the coating process and ensures clean threads or machined areas.
The coating process has either an automatic system or a professional finisher, which spray the grounded metal parts with charged powder coating. The coating sticks to the surface through electrostatic bonds.
Curing melts the resins in the powder and turns it into a durable coating. The timing and temperature used for curing depend on the coating thickness, substrate material, item size, and other factors. Professionals use these aspects of the part to calculate the precise curing time. After curing, the part cools and moves on through packaging and shipping.
Reach out to Keystone Koating for commercial or industrial-grade powder coating services. Our eight-stage pretreatment process ensures quality adhesion of powder coating that lasts. Plus, we can provide quick turnarounds for large-volume orders. With our turnkey solutions, your business benefits from a complete coating process that starts with blasting and ends with packaging and shipping. We’ve been trusted for over 30 years on industrial or commercial projects such as yours. Contact us for a quote
You will get efficient and thoughtful service from ZHYAO.
Coating line means a series of one or more coating applicators and any associated flash-off area, drying area, and/or oven wherein a coating is applied, dried, and/or cured; a coating line ends with the end of the drying or means a series of one or more coating applicators and any associated flash-off area, drying area, and/or oven wherein a coating is applied, dried, and/or cured; a coating line ends with the end of the drying or curing area or prior to the beginning of the application of the next coating. It is not necessary to have an oven or a flash-off area in order to be included in this definition. This shall include, but is not limited to:
Powder coating eliminates the mess and imprecision of traditional painting processes. The liquid-free finishing process offers increased durability, colorfastness, and efficiency. Powder coating lines build on the efficiency of the process with the addition of a production line. Parts and assembled pieces move through a powder coating line on a conveyor system to maximize turnaround times without sacrificing the high-quality results powder coating offers.
Professionals use powdered thermosetting polymers, plastics and additives to create a hard, pigmented coat on metal surfaces. The basic process uses ESD (electrostatic spray deposition) technology to apply the powder to the surface of the product. The powder will fall off the product at this stage. Heat changes the chemical nature of the powder and allows it to bond to the surface of the metal and create a strong molecular structure.
Powder coating is a multi-step process. Each step ensures the powder adheres to and transforms the surface of the part. All powder coating processes use roughly the same steps, but automated powder coating lines increase productivity for high volumes projects and can handle more parts at one time. Consider the process:
Powders will not properly adhere to dirty, rusty, or lubricated parts. Professionals must thoroughly strip and clean the product before sending it into a powder coating process. Powder coating lines may include a multi-step cleaning process involving sandblasting for rust and debris removal, degreasing, washing, chemical etching for improved adherence, and/or phosphating for corrosion prevention.
A debris- and chemical-free surface will allow the powder to sit evenly and bond better during the heating process. Automated preparation programs take the guesswork out of preparation and cleaning processes. The parts move into the cleaning system and receive uniform treatment and drying before entering the next stage of the powder coating process.
Powder coating lines use conveyor systems to pull parts directly from the preparation process into a powder coating unit. The surface area of each product is manually powder coated to ensure complete coverage. Technicians must adjust sprayers and pigmentation levels to create single- and multi-color applications for various metal substrates.
The last stage of the powder coating process adheres the powder to the metal product. A powder coating conveyor line will move the batch from the coating unit to an appropriately heated bake oven for curing. Heat allows the polymer system to permanently bond to the metal and offer a sleek, uniform, and durable coating without drips or blemishes. The product leaves the oven and cools before leaving the powder coating line for packaging or assembly.
Powder coating lines feature some form of preparation, coating, and curing stage, but the individual approaches within each stage may vary. The line can conduct all three stages simultaneously to deliver continuous output for high-volume parts orders. Strong line systems feature durable and heat-resistant conveyor systems that carry the product movement through each stage. The size of the system dictates the quantity and size of the metal pieces that qualify for automatic line service. Powder coating lines can enhance any metalworking project with durable, even, and visually appealing finishes.
Swanton Welding Company, Inc. offers a complete powder coating line system in addition to other standard painting options. We use high-quality powder coating sprayers and a Stage 1 heated conveyor oven to coat and recoat metal pieces of all kinds. Reach out to us at (419) 826- today to learn more about our powder coating finishing services.
It goes by many names: prepainted metal, coil coated metal, prefinished metal. Each of these descriptions refers to the product of a Coil Coating Line, sometimes called a continuous coil line (CCL). Prepainted metal is commonly used as a coated product in construction applications (metal walls and roofs are two examples), as well as appliances, HVAC units (air conditioners, furnaces, etc.), rainware products (gutters, downspouts, flashing, etc.), and many others. Prepainted metal is the product; a CCL is the application process used to produce prepainted metal.
As its name suggests, the CCL process for prepainted metal is continuous, but what does that actually mean? It probably seems obvious—continuous means “not stopping” or “never ending”—but how does a coil coating line make this happen? It’s not like there is such a thing as an infinitely long coil of metal. Surely, some part of the process must stop when a coil of metal is completely processed and another new, unprocessed coil must be started.
The word “continuous” refers to that segment of a coil coating line that stays in a steady-state condition: the cleaning, pretreating, painting, curing, and cooling. Engineers love steady states because all the processing conditions remain constant throughout this segment, and a constant, unchanging process is one of the secrets to producing high-quality prepainted metal at very fast line speeds.
Still, what happens when one coil has been completely processed and another must be started? Imagine watching the fascinating engineering that makes the CCL continuous.
Here’s the scenario. You’ve now painted about 17,000 feet (about 3 miles of metal) from a coil that is at the entry end of the CCL. The tail end of this coil is about to run out, and another coil must be put in its place. To accomplish this, you must find some way to keep the steady-state part of the coil line running while the entry end of line stops. The answer is genius: the CCL uses an accumulator, a piece of equipment that “accumulates” a certain amount of metal. It is a set of upper and lower banks of rolls through which the metal strip is threaded in a serpentine fashion, and it stores lengths of metal as the two roll banks are spread apart. The total stored length of metal depends on the design speed of the line—usually 60 seconds of steady-state metal processing time. When the entry end of the continuous coil line stops (is that an oxymoron?), the roll banks move toward each other, and the stored metal in the accumulator continues to feed the steady-state portion of the CCL.
Magura, Daniel & Fedák, Viliam & Kyslan, Karol & Sanjeevikumar, P. (). “Practical Experience with Control of Drives of an Accumulator in a Web Processing Continuous Line.”
In those 60 seconds, a lot of things have to happen at the entry end, which is now not moving at all. The new coil is loaded onto the CCL. The front end of this new coil must be attached to the tail end of the earlier coil. This attachment may be made by mechanical press-type joint (sometimes called stitching) or by welding the two ends together. And the attachment must happen quickly. If the accumulator runs out of metal, and if the two coils (the old and the new one) are not joined, the CCL must be stopped, which, of course, negates the concept of “steady state.”
As the coils are successfully joined, the CCL continues to operate. The first task of the newly joined coils is to replenish the accumulator. Remember that it has fed the steady-state portion of the coil line while the new coil was loaded onto the line, but it is now nearly empty (i.e., the length of metal in the serpentine arrangement of rolls is very small). It must be replenished in anticipation of the next time a coil is consumed and a new coil is loaded and joined to the old coil. This is done by running the entry end of the CCL at a much faster speed than the steady-state portion. This is referred to as overspeed, and it is typically 25% up to 100% faster than the steady-state portion of the line.
So, imagine that you are standing near the accumulator and you see the steady-state portion of the line is running at 600 feet per minute. The accumulator is empty, but that serpentine ribbon of metal and the rollers start rising higher and higher from the ground level as metal from the entry end of the CCL is fed into the accumulator. When the accumulator is filled, the line speed at the entry end returns to the same as that of the steady-state portion of the CCL. It truly is an engineering marvel.
But wait; there’s more. We have explained adding a coil to the line, but how does one remove a coil from the exit end of the line after it has been cleaned, pretreated, and painted? You guessed it: There is not only an entry end accumulator, there is also an exit end accumulator. Basically, the same process occurs at both the entry end and the exit end, but in reverse of each other. The exit accumulator collects metal from the continuous process, allowing the non-continuous processes of changing coils at the exit end of the line. Fascinating stuff!
Other painting processes are also continuous. A spray line, for example, is nothing more than a giant conveyorized loop, where bare parts are hung onto the line and then cleaned and pretreated. The conveyor eventually carries them into a spray booth, where the paint is applied. Then the parts travel into very large baking oven, where the coating is cured. Then the parts are cooled and unloaded.
The big difference between a CCL and a spray line is the rate at which the metal can be processed. A CCL typically can coat 10 times as much surface area as a spray line in the same amount of time, and it does so at essentially 100% efficiency (i.e., no loss of paint during the painting process). That’s why a CCL is emblematic of an engineer’s mantra: Better (consistent cleaning, pretreating, painting, curing, and cooling), faster (line speeds, meaning more metal area painted), cheaper (maximized utilization of energy)!