Layout 1

This technique requires little equipment
other than the bed, a source of air, and a
means of heating the parts. A variation of this
technique is to apply a negative electrostatic
charge to the powder which draws the powder
particles to the part via electrostatic attraction.
2. Electrostatic spray: An electrostatic
charge brings the particles and the part together.
One benefit is that the parts are
coated uniformly — even on the back side of
the part — because the attraction between
the powder and the part is uniform, all around
the part. Then the part is heated so that the
powder melts, fusing to the part surface.
This is the application method of choice
for coating many parts at once, or when the
coating thickness needs to be controlled.
Spray gun
Power supply
Electrostatic spray
Air/powder input
Electrostatic
charge
Diagram of typical electrostatic powder application process.
Advantages vs liquid coatings
Powder coatings offer several advantages
over liquid coatings in terms of performance,
ease and efficiency of use, cost, and environmental
concerns.
1. Better performance from higher film
thickness: Powder coatings provide the same
level of corrosion, wear protection, and release
as their liquid counterparts — if applied
at the same film thickness. However, in comparison
to liquid coatings, powders make
thicker films possible because they tend not
-3-
to run, drip, or sag.
Overall coating thickness can be built to
maximum levels allowed by the resin without
fear of blistering. In general, powder-coated
parts are more resistant to cracking, peeling,
and marring during handling and normal use.
Thicker coatings also tend to be tougher and
more durable and are particularly useful on
corrosion-prone applications where thicker
coatings provide added protection. They also
help cover small surface defects such as
sharp edges, dimples, and machining marks.
As a result, some secondary machining operations,
such as polishing, grinding, or deburring
may be eliminated.
2. Advantages in deep-well applications:
Powder coatings can be advantageous when
applied to parts that have recesses and depressions
(see page 7). Using the fluidizedbed
method of application,
powder coatings can be applied
almost evenly to channels, keyways,
holes and other recesses.
No other application method results
in coatings as uniform and
blister-free in these areas. This is
because coating thickness depends
primarily on the heat in the
part, not on electrostatic attraction
or how well volatile carriers
Powder surrounds
part, attracted
electrostatically
are driven off, as is the case with
liquid coatings.
3. Easier to use: Cleanup is
greatly simplified with powders.
Cleanup of liquid coatings often
requires stripping agents and solvents that
must be discarded. In contrast, a powder
booth or spray area can be cleaned up by
simply vacuuming the powder overspray.
4. More efficient: If the powder overspray
is not contaminated, it can be collected and
recycled (liquid coatings cannot), so it is possible
to use nearly 100 percent of the coating
material.
5. Low capital investment: Many of the advantages
of powder coatings lie in what they
enable users to avoid. For instance, powder