Electro Coating Plants
Electrocoating – (Also known as Elpo, Electro dip, KTL, or Electrophoresis )
The Electrocoating system was developed in the U.S.A. approximately 50 years ago. The first plant was for the processing of wheels and soon afterwards full Auto body plants went into production.
The development of the Electrocoat technology provided improved corrosion protection especially in recessed areas.
The initial system used anodic electrodeposition, but was replaced by the superior stability of cathodic formulations in 1973. The film build can be adjusted within the specifications of the formulation used.
The process is similar to electroplating, the main difference being that electrocoating deposits organic resin molecules instead of metallic ions. The paint plating type operation allows for the object to be dipped into the electro dip water-thinned paint. The object to be painted is charged -ve i.e. the cathode, and the paint solids +ve i.e. anode and therefore deposits onto the cathode.
The electrical supply is a regulated and smoothed direct current with the facility to adjust the voltage for film build considerations. Cathodic electrocoat paint consists of resin, pigments, coalescing solvents and demineralized water.
The Electrocoat process is a one coat system and is therefore used mainly for the application of prime coats. There are, however, numerous small parts plants that require only single – one coat finishes with high corrosion protection all of which falls within the Electrocoat capability.
Major advantages include:
- High corrosion resistance at low film build, based on good pre-cleaning and phosphating before processing through the Electrocoat system;
- Corrosion protection in recessed areas.
- High transfer efficiencies in excess of 95%.
- Water based material eliminating fire risk and reduced cost for controlling pollution.
- Electrocoat deposited paint is insoluble in water, allowing efficient rinsing of dragged-out paint.
- Coatings will not sag during deposition or the baking process.
- The film build is reproducible on a continuous basis.
- Labour costs are minimal due to the fully automated process.
Electrocoat ancillary equipment:
- Chiller plant (Required to maintain the paint temperature within the required limits).
- Ultra Filtration Plant (For control of water-soluble impurities and production of ultrafiltrate to operate closed-loop rinsing after the main paint bath).
- Standby generator (Continuous operation of the circulation pumps and chiller plant is required).
- D.C. Rectifier.
- Anolyte system (circulation of anolyte to the anode cells).
- Demineralized plant with storage tank and pump circulation.
- Pigment and resin feed pumps.
- U,F, Rinse tunnel with pumps and related controls.
- Main pump circuits with filters, heat exchangers and controls.
- General enclosures and ventilation.
Continuous E-coat plants refer to a continuous overhead conveyor plant whereby the parts are loaded at the loading section and then transported through the complete process all the way to off-loading before human intervention is required. This type of process is more suited to high volume/throughput parts which are smaller in size.
Batch E-coat plants refer to the process type where batches of parts are dipped in the process tanks. This system usually incorporates an overhead transporter system or in lower capital investment type installations the parts may be dipped by the operator using an electric crawl and hoist system. This process is normally used for larger parts.