Tribo-charge gun vs. Corona Spray Gun

The most popular powder coating systems are the triboelectric or corona/electrostatic charging spray guns. These systems have been used for several years and have both seen significant improvements over these years. When deciding to purchase a spray gun, possible the most important question to answer is, which one would be right for you and your business? To answer this question, first it's important to understand the basic principles behind of each type of spray gun and the type of results each delivers.

Corona/ Electrostatic: The corona spray gun has an electrode located near the tip of the gun. This electrode is charged with a high voltage, low amperage power unit, which emits a field charge that imparts a negative charge onto the particles of powder that results in the powder being attracted to the grounded work piece. Positive polarity generators are used primarily for charging nylon powders.

The corona spray gun works by producing a corona discharge which is an electrical discharge brought on by the ionization of the powder surrounding the electrode, which occurs when the potential gradient exceeds approximately 30 kV per centimeter, however these conditions are insufficient to cause complete electrical breakdown or arcing.

Powder particles exiting the gun travel near the electrode where they accumulate a negative charge. However, not all of the powder particles accumulate a charge as some are shielded from other particles in the charging zone. These particles may be carried and deposited onto the object through the flow created by the charged particles, similar to a tree branch being carried in a river current. Tribo: Tribo-charging guns create a charge on the powder particles via intimate contact with polytetrafluoroethylene from the gun walls. This occurs when the two differently charged materials are brought into contact, and a transfer of electrical charge occurs eliminating the imbalance between the two objects. The degree and direction of the charge transfer depends greatly on many factors, such as the chemical and electronic structure of both materials.

Polytetrafluoroethylene or PTFE, which is commercially known as Teflon is typically used as the powder contact walls in a Tribo gun. The powder particles are a composition of resin, pigment, fillers, and depending on the type of effect could include other additives such as metallic flecks. Most finishing powders become positively charged when they come in contact with the Teflon walls.

Tribo guns charge the powder particles when the powder particles contact the Teflon walls. The more contact the powder particle makes with the walls the greater the charge on the particles. As long as there's Teflon in the gun for the powder to make contact with, the powder will become charged. For this reason, the airflow from the gun plays a very important with a Tribo gun transporting the powder particles onto the object being coated.