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Painting

Cataphoresis: electro static painting or e-coating (KTL)

Cataphoresis painting, or e-coating, is a surface treatment that gives base metal surfaces resistance to chemical and environmental corrosion.

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The cataphoresis process is an electrodeposition of paint in immersion with a continuous electric current. The deposited film gives the artefacts high anti-corrosive characteristics, prolonging over time the preservation of even those parts that cannot be reached with a traditional spray system (box sections, deep bends, sheet metal couplings).

This cutting-edge technology is used on all car bodies and on artefacts in other industries such as: industrial vehicles, motorbikes, furniture, tractors and agricultural machinery, and where complete and excellent rust protection is required.

Treatment cycle of the cataphoresis process

According to the daily production schedule, the warehouse workers pick the material designated for cataphoresis and deliver it to the appropriate work areas adjacent to the cataphoresis plant. The material is placed in well-defined areas and sorted according to weight and/or overall size. These areas are equipped with mechanical systems to facilitate loading operations.

Once in the designated areas, the cataphoresis workers perform a qualitative and quantitative check of the material to be coated. In fact, for optimal cataphoresis, the material must have certain characteristics (absence of oxidation, calamine, writing or paint marks, etc.). If the material is suitable for the cataphoresis process, the workers proceed to hang it on special sling bars in the manner defined in the production schedule.

All equipment used for a machining cycle is always cleaned and maintained by an in-house grit-blasting service. This is necessary to keep the structures free of paint deposited during previous painting operations which can create electrical insulation, preventing electrical continuity between the material and the sling bar.

After the pieces have been hung, the employees attach an identification tag to each sling bar or specific container which shows the customer code, article code, number of pieces and, if necessary, an indication of further processing of the material.

Once the preliminary hanging operations have been completed, the material is sent to the cataphoresis system via an automated feed system.

7-stage pre-treatment phase

The pretreatment phase consists of 7 different steps to prepare the material to best receive the subsequent cataphoresis treatment:

  1. Hot degreasing with alkaline products in water solution (pre-degreasing);
  2. Hot degreasing with alkaline products in water solution;
  3. Washing with demineralised water and an activator;
  4. Phosphating with zinc-manganese-nickel salts (tricationic/trimetallic);
  5. Washing with demineralised recycled water and passivating agent;
  6. Washing with demineralised water;
  7. Washing with demineralised water and drip drying.

Water from the pretreatment stages is collected in tanks located outside the plant. Physical and chemical parameters related to the pretreatment phases are monitored on a daily basis.

Epoxy paint immersion electrodeposition phase

Once the pre-treatment phase is complete, the material moves on to cataphoresis treatment. The material is immersed in the cataphoresis tank long enough for the paint to be electrodeposited by means of a direct current. The film of paint deposited after immersion in the tank gives the materials excellent anti-corrosion properties, prolonging the preservation of parts that cannot be reached with traditional spray systems (sharp bends, sheet-metal couplings, box sections).

Post-treatment washing phase

The cataphoresis treatment is followed by three washes to remove excess paint. The first two washes are carried out using an ultrafiltrate and the last wash uses demineralised water.

Polymerisation phase

The material is sent to the final curing stage. This stage, necessary to dry and cure the paint, takes place in a tunnel oven with forced air circulation at 180-200°C.

Upon leaving the cataphoresis oven, the material is checked for compliance and either sent for further processing such as liquid or powder enamelling, packaging and shipping, or temporarily stored awaiting shipment.

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