One of the key technologies of anti-corrosion coatings is the so-called e-coat also known as e-coating, electrocoating or electrodeposition coating. It is a process (immersion) of applying a liquid coating to a metal surface by use of electrical current. Electrically charged paint particles of resins and pigments are deposited out of a water emulsion to coat a conductive substrate. Paint film thickness is regulated by the amount of voltage. The deposition is self-limiting and slows down as the applied coating electrically insulates the part. E-coat particles deposit firstly in the areas closest to the counter electrode. As these areas become insulated, particles are forced into more other bare metal areas. This phenomenon is known as throwpower and is a critical aspect of the e-coat process. The process is cationic or anionic. The cationic e-coating process is used in 90%, while the anodic in only 10% of applications.
Benefits of e-coat
There are numerous benefits of the e-coat including cost efficiencies, production efficiencies and environmental advantages.
The main advantage of the e-coat is that the process produces uniform finishes with excellent coverage and certain film thickness. High transfer efficiency, 100% coverage (including recessed area and sharp edges) and control of the film builds increase significantly corrosion protection and aesthetical properties of the final products.
Also the method is extremely effective in terms of resources use due to not only high transfer efficiency and self-limiting ability but also because there are no runs, drips or sags, non-uniform line loading and usually one or two coat applications are sufficient for the optimal performance.
The method is user-friendly automated system where low maintenance and minimal labour are needed. Faster production line speeds, dense racking of parts and low manpower requirements increase the line productivity. Usually, e-coat lines require higher initial costs but when consider variable costs (transfer efficiency, line efficiency, maintenance), the e-coat process come out as the lowest costs option for coating.
Furthermore, the excellent corrosion protection together with the line productivity bring environmental advantages of the epoxy e-coat. The products are durable and long-lasting and hence enable reduction of CO2 emissions and waste from the new product manufacturing. E-coat formulas are usually zero VOC (volatile organic compound) and HAPs-free (hazardous air pollutant) or low-VOC and reduced HAP. Compare to solvent-based coatings, this reduces air pollution. Share of the paint components utilized in the e-coat process is estimated to more than 95%. Such a raw material use efficiency reduces waste production, need of water use and waste water treatment and water pollution.
The e-coat process offers other important advantages: lead-free, heavy metal-free, reduced fire hazards, reduced exposure of workers to hazardous materials.