CORONA VS TRIBO

Corona Charging

This kind of charging is made by pushing the uncharged partilces (powder) through an electric field created by high voltage circuit. The powder is then be charged and trend to the grounded objects.

Advantages

1) Strong electrostatic field results in rapid charging and deposition

2) Electrostatic fieldlines support the powder particles to move towards the work piece

3) Simple repairs of the powdered surface are possible

4) Light, robust spray gun

5) Accepts different types of powder materials and particle sizes

6) Film thickness can be simply changed by voltage variations

7) Simple construction is suited for fast colour changes

Disadvantages

1) Redundant ions generate a self-limiting effect

2) Strong fieldlines lead to Faraday effect (irregular coating, corners and crevices are not properly covered)

3) These effects can be reduced or eliminated respectively by voltage changes or use of anti-ionisation rings (to reduce Faraday and Orange peel effect)

Tribo Spray

In Tribo charging, the powder is charged by friction. Particles (powder) moves through the spray gun will rub against the media in the gun and get charged.

Advantages

1) No Faraday effect; deep crevices, corners and hollow spaces can be better penetrated

2) Powder can be better directed by the use of directional finger sprayers and aerodynamics

3) Less, if any, fat edges on the coated surface

4) Uniform coating

5) Very good automation possibilities

6) No high voltage generator required

7) Higher film builds possible without back-ionisation

8) Higher productivity by closer arrangement of objects

9) Better flow; practically no orange peel effect

Disadvantages

1) Performance is strongly influenced by uncontrolled air-streams

2) Special powder is necessary; formulation must be adapted to the Tribo charging process

3) Particles smaller than 10 microns are difficult to charge

4) Powder deposition slower than for corona

5) Colour changes take a long time

6/ Charging dependent on atmospheric moisture

7// The quantity of powder that can be charged from tribo guns is less, more tribo guns are required to coat.