Manufacturers today employ a variety of finishing processes to modify the exterior of a metal workpiece in order to obtain desired qualities. Painting represents a widely used surface treatment, for instance.
One specialized type of painting utilized by some metal parts fabricators had become known as "e-coating". Also called "electrodeposition", "electropainting" or "electrophoretic coating", this surface treatment gained importance recently.
The E-Coating Process
E-coating enables a manufacturer to improve corrosion resistance by employing an electrical field to coat metal using specialized epoxies or paints. A number of companies have developed proprietary formulations for this purpose.
Typically, the e-coating process entails several steps. (The requirements for applying individual specific proprietary formulations impact this process significantly. The usual steps involved in applying e-coating successfully within an industrial setting include:
Ordering Metal Parts
Manufacturers typically begin the process of e-coating by arranging mental parts along an assembly line.
Pretreatment And Cleansing
Part fabricators perform pretreatment and cleansing operations required for the deposition of specific proprietary paints or epoxy formulations. For instance, some brands adhere more effectively with pretreatment procedures which include coating the metal surface with a specialized formulation of zinc phosphate before rinsing the workpiece with water and mineral-free water.
Paint Application And Rinsing
Typically during e-coating, the manufacturer deposits paint (or an epoxy) onto the surface of the metal by submerging the workpiece in a bath filled with the desired substrate. Applying an electrical current directly through this vat causes the charged particles to adhere to the surface of the metal. The manufacturer then retrieves the coated part and rinses away excess material. Control over the voltage level and the immersion period enables the manufacturer to closely regulate the thickness of substrate deposition.
A Dehydration Oven
Water-based substrates may necessitate the use of a specialized dehydration oven. This step helps eliminate moisture from the workpiece surface.
A Cure Oven
The production protocol may require the metal part to remain at specific temperatures for designated periods of time within a curing oven in order to promote the completion of chemical changes within the electrophoretic coating. Frequently electrostatically applied paints and epoxies harden more effectively at controlled temperatures. For example, the application of heat may cause some components of the paint or epoxy to form new bonds which enhance surface hardening or improve corrosion resistance.
Anodic And Cathodic E-Coating
The bath used during the e-coating procedure permits substrate deposition through the creation of an electrical field. As an electrical current passes through the bath, the substrate forms an attraction to the metal surface of the workpiece, which serves as either the anode (in anodic e-coating processes) or the cathode (in cathodic e-coating processes).
Materials And Applications
The e-coating finishing process developed comparatively recently. The invention of proprietary epoxy and paint formulations designed specifically for electropainting contributed to its growing popularity. Today e-coating manufacturing environments frequently utilize automation.
E-coating can transform the surface of any fabrication material capable of conducting electricity: aluminum, copper, brass, tin, nickel, steel, and more. The substrates employed during e-coating may occur in either powdered or liquefied forms. This finishing process does require the generation of an electrical field. Manufacturers usually rely upon electrified baths to perform e-coating in mass production environments.
Today corrosion-resistant epoxy and acrylic paint formulations predominate as the preferred e-coating bath substrates. These materials help protect metal surfaces against corrosion. In some cases, they also contribute significantly to the aesthetic appearance of the automobile. Some companies market proprietary e-coatings designed to enhance the ease of maintaining automotive products in attractive, corrosion-free condition.
E-coating reportedly has achieved the widest acceptance within the auto manufacturing industry. Preliminary experimentation with the application of water-based resins through electrophoretic deposition occurred during the 1920s and 1930s. (Previously the process had focused mainly on tire production.) Interest in electrophoretic deposition resurged during the 1950s and in 1963 an automaker launched the first commercial fabrication facility to utilize an anodic e-coating process. During the 1970s, automakers reportedly invested heavily in electropainting technology to promote the application of specialized primers to vehicles during mass production. Most auto manufacturers switched to cathodic e-coating systems during that period.
Recently, some other manufacturing sectors started utilizing e-coating more widely to protect the surfaces of metal components from corrosion or to apply hard colorful paints. Today e-coating occurs not only in the automotive sector, but also in fabrication plants producing heavy construction equipment, agricultural implements, buses, trucks, office equipment and some consumer items.
The Advantages of E-Coating as a Finishing Process
E-coating offers some important advantages:
- The use of electrified baths permits manufacturers to obtain very uniform, complete surface coatings of metal workpieces. Although e-coating can occur on a small "low tech" scale, in large production environments this process permits the use of extensive automation. Electrified baths enable fabricators to completely coat a workpiece with a desired substrate.
- Investing in e-coating systems may reduce an individual manufacturing facility's labor costs over the long term. This finishing process works well in conjunction with robotics, for instance.
- E-coating with the assistance of an electrified bath permits a manufacturer to closely control the thickness of deposited coatings. By adjusting production parameters, for example, a fabricator may provide specific coating thicknesses for different components within an assembly.
- Today the substrates used during e-coating sometimes significantly extend the anticipated product lifespan. For instance, some coatings offer enhanced surface corrosion resistance.
- The e-coating process utilizes production resources efficiently. It assists manufacturers in conserving raw materials effectively.