Today industrial parts manufacturers enjoy access to a broad array of processes for modifying the exterior of a metal workpiece to achieve desired qualities in a finished component. Finishing serves a variety of different potential objectives. For instance, a fabricator may seek to improve corrosion resistance, extend the useful lifespan and wear resistance of a part, or provide increased surface electrical conductivity.
In many cases, the finishing process creates more attractive surfaces. This process potentially increasing marketability. Powder coating, an additive process, constitutes one widely used type of surface treatment. It may offer a number of useful surface properties in addition to improving the overall aesthetic appearance of a metal part.
Powder coating involves the application of thermoplastic or thermoset polymer powders to metal or plastic exteriors. Currently most industrial manufacturers apply dry powder to metal with the assistance of electricity and heat. The powder particles cling to the surface and melt, forming a film of fused particles. In general, this process encompasses three distinct phases:
In order to apply a powder coating, a manufacturer first prepares a metal surface to accept the powder. This step also removes dust particles, grease and other debris which might interfere with even coatings. Typically, pretreatment involves the use of abrasive chemicals and/or mechanical processes, such as sandblasting. Cleaning, rinsing and (sometimes) preheating all enter into this phase.
Manufacturers apply powder to metal surfaces using a variety of different technologies. One popular method employs spray guns which apply an electric charge to particles expelled forcefully towards a grounded metal surface. Preheated parts may also be directed through a “fluidized” bed of airborne particles.
Curing involves maintaining a part within designated temperature ranges for specific periods of time to permit a coating to flow and bond evenly across the surface. The curing time varies based upon the heating technology and the materials utilized during powder coating.
The most popular powder coatings in industrial manufacturing environments rely upon either thermoplastic or thermoset polymer powders. Both materials offer distinct advantages and disadvantages:
Theremoplastic powders simply melt during the heating process. They flow across the entire exposed surface of a metal component. However, these powders retain their chemical compositions after curing. Manufacturers usually apply thermoplastics, such as nylon powder coatings, to metal surfaces which have undergone preheating. Thermoplastic powders typically create recyclable coatings displaying heightened impact resistance
Thermoset polymer powders after melting undergo chemical changes. The particles in the powder cross-link with one another or fuse with additives, helping to toughen the surface covering formed on a metal exterior. One advantage offered by thermoset powders: this material will not soften and liquefy if subjected to re-heating after initial application. Thermoset coatings in most cases cost less than thermoplastic coatings. Today manufacturers rely extensively upon four broad types of thermoset polymers in creating powder coatings: acrylic (widely used in the automotive industry), polyester, epoxy and fluoropolymer.
Industrial manufacturers frequently apply powder coatings very cost-effectively. This finishing process has achieved acceptance around the world as a way to enhance the appearance and functionality of metal components.
Powder coating sometimes takes place on a “low tech” hobbyist scale, but typically in modern industrial settings applying these finishes entails extensive automation. The type of powder used will typically dictate the materials required in order to prepare the metal surface. In its most basic form this process requires the use of an oven, preparatory equipment (such as sandblasting machinery or abrasive chemicals for pretreatment), and specialized powder application tools (e.g. an electrostatic spray gun or “corona” gun or a fluidized bed).
The curing times required for powder coating also varies widely, depending upon the type of powder and the available heating technology. Today many production facilities shorten curing time through the use of lasers to heat thermoset powder, for instance. A manufacturer performing powder coating must possess the means to closely monitor temperature levels to achieve satisfactory results.
Numerous industrial parts, tools and items of equipment benefit from the powder coating process. Manufacturers generally use powder coating in lieu of painting to finish metal surfaces in order to gain desired surface qualities, such as enhanced resistance to daily exterior wear and/or a more attractive appearance.
Popular commercial applications for this process include coloring aluminum extrusions and coating heavy equipment, automotive parts, and agricultural implements. Powder coating allows manufacturers to generate products for outdoor use capable of retaining vivid surface colors despite protracted exposure to inclement weather. It also helps create stylish consumer metal household items. For example, powder coating permits designers to develop kitchen and laundry appliances which appeal aesthetically to the consumer marketplace.
Powder coating holds a number of important benefits as an industrial finishing process.
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