The process of e-coating application
Surface preparation – is one of the most critical steps prior to the application of coating on the product. Surface preparation is also an important step in other coating applications that make use of liquid paint or powder coat. There are different techniques and technologies employed in surface preparation but the choice will depend on the application and the substrate. In most cases, the substrate is chemically cleaned to ensure the quality of adhesion.
Dry-off – requires E-coat Equipment in the form of a drying oven so that the clean parts can be dried off before it enters the electro-coating area. The kind of paint and the part characteristics will determine if there is a need for drying otherwise the parts can be brought directly to the e-coating area for the application of paint.
Application of electro-coating – E-coat Equipment that is necessary to the process of application is the tank that is usually constructed from steel plate with an inner lining of chemically resistant, dielectric material. The tank itself must be electrically grounded with a size that can accommodate dwell time and part dimensions. Current will flow from a power supply to an electrode, through the paint to the part and through the part back into the power supply. In this process, resin and pigments migrate to the part where a uniform film will be deposited. There are two types of e-coat paint that can be used; the cathodic and anodic. Cathodic paint is more corrosion resistant while anodic paint is less expensive and does not require an anolyte system.
Curing – one of the most important E-coat Equipment is the curing oven. E-coat is essentially a liquid paint which requires curing after it has coated a part. The curing cycle is based on the type of paint chemistry used. For example, if an acrylic-urethane type e-coat is used it will require a curing temperature of about 320oF for 20 minutes. The energy used in curing the e-coat will depend on part size and geometry. A part with a simple geometry can be cured completely through the use of infrared heating. Infrared heating works through line of sight and heats the metal surface without the need to heat the whole part. On the other hand, a convection oven is a better choice for curing parts with complex geometries since heat will reach all areas of the part. In order to obtain optimum coating properties, a full cure is important with both time and temperature considered during the curing process.