You probably own a workshop or have a construction project and
are stuck in the painting phase. You know you want to use powder paints, but
you are unsure what type of powder-coated gun to use. Below is a breakdown of
the differences between how tribo and corona powder coated guns
Powder Output and Application Speed
Corona guns take the day in the fight between tribo and corona
powder-coating guns for powder output. The rate at which a gun produces powder
determines the amount of powder that will contact the work surface. Corona guns
can consistently
charge powder particles and operate at both high and lower power output modes.
However, tribo guns are much slower due to restrictions on the
flow of powder output. The reason for flow restriction is that the gun forces
the powder to flow through several tubes, rotates the powder inside the inner
tube using air, or creates dimples, thus disrupting the flow of the powder through
the tube. Switching the tribo gun to a low power output increases the risk of
getting the powder charged due to rubbing against the walls of the gun. The
high power output mode doesn't help much either, because the flow restriction
limits disrupt the higher speed, thus lowering the power output.
Due to these differences, you’ll need more tribo guns to apply
the same amount of powder that a single corona powder gun will apply,
especially at high line speeds. Corona guns can be applied at low and high conveyor
speeds, but you will need a tribo gun to achieve thick coatings.
Powder Types
The type of powder will dictate whether to use a corona or a
tribo gun. This is because tribo guns are limited to specially formulated
powders specifically made for this type of powder-coated gun. Remember, this
gun doesn't create charges between dissimilar materials, limiting tribo guns'
applications.
On the other hand, if you need to perform special operations, go
for corona guns because they are capable of pretty much anything from frequent
color changes to the application of different types of powders.
The Faraday Cage Effect
The corona powder coating gun is more limited by the Faraday
cage effect than the tribo gun. This means that you can use the tribo powder
coating guns to coat surfaces highly affected by the faraday cage effect, such
as supporting seams for shelves, corner inboxes and radiator fins. This is
because a tribo powder
coating gun does not generate an ion field between the product and the
gun, since the ion field is responsible for increased electrostatic repulsion.
Initially, the powder particles are attracted to flat
surfaces. However, the electrostatic repulsion, which works on particles with
similar charges in intense air flows or areas, forces the particles out of the
seams and corners. Luckily, the Faraday Cage Effect can be lowered in corona
powder-coating guns by operating them at lower power output. This removes the
ions from the equation, leaving the airflow dynamics at work.
The Quality of Finishes
The two guns differ in quality finishes, with the tribo guns
being effective for thinner, finer finishes and tribo for thicker finishes. A
corona gun will produce a consistent film build for thinner film thickness.
While other variables such as particle output charges, environmental
conditions, and conveyor speeds will influence the level of consistency, corona
powder guns can effectively make adjustments to ensure a nice smooth finish.
However, the corona gun cannot achieve thicker finishes because
of back ionization. The gun creates high charging
fields when
new powder particles accumulating on the work surface dissipate their charges
through the existing powder film. This limits the amount of powder you can
apply and still maintain a smooth finish since back ionization creates micro
craters or a wavy appearance at 3 mil finishes and above.
Tribo guns, on the other hand, don't create an electrostatic
field because they don’t charge the powder particles and thus they's not
affected by back ionization. This results in smoother, thicker finishes.
The Prevailing Environmental Conditions
You should carry a corona gun with you if you work in harsh
environments. While experts recommend all coating operations to be conducted in
controlled environments, it is not possible sometimes. And variables such as
humidity, type of material, and room temperature will affect how both guns
perform. The corona gun is immune to environmental factors since it doesn't
rely on the charge creation of powder particles.
Remember, tribo guns work by creating charges on the powder particles.
Varying environmental conditions interfere with the charging effectiveness, and
the transfer of powder particles to Teflon material is especially difficult
with varying environmental conditions. The result is inconsistencies in the
powder coating over time.
Bottom Line
While the corona powder application gun seems to win over the tribo application gun, remember both have their strengths. The corona powder application gun effectively applies thinner finishes and can use different powder paints with different colors. It is, however, affected by back ionization and doesn't work well in areas with a high Faraday cage effect. On the other hand, the tribo guns can work on crevices, corners, and radiator fins and produce a thicker consistency. However, it's limited by airflow dynamics and works slower than a corona powder application gun. You can now make an informed decision!
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