We have had several conversations recently
about the benefits of powder coating vs painting. What exactly is powder
coating? And why is it more durable and longer lasting than paint?
The material that most
powder is made from is basically “plastic”. Polyesters are chemically
related to plastic and have an extremely strong chemical bond. Some may
remember the wonderful but hideous polyesters of the 1970s. While some
inexpensive polyesters and plastics are rigid and brittle, there are
many forms of plastic such as kevlar, nylon and plexiglass that are
strong and flexible. The molecular bonds that make plastics so durable
also make them extremely resistant to the natural process of
decomposition. This is one reason why powder coating is so long lasting.
Most quality powders are
made from pure or blended polyester resins. These start out in liquid
form and are poured into molds to dry. Imagine a huge ice cube tray.
Then the blocks of dried resin are ground into a fine powder by a giant
blender. Different colors can be made by mixing pigment during the
liquid resin stage or by mixing powders. The multitude of chemistries
make powder mixing somewhat dicey. The various chemistries in different
powders and metal flakes repel each other and create vein and hammertone
effects. Textured powders are made by mixing powders of different
chemistries after they are ground.
When powder is applied to
metal and placed into the oven for cure, it melts together to form a
continuous and resilient seal against moisture, rust and corrosion.
Unlike paint, powder does not contain chemicals that evaporate during
cure -once powder is cured in the oven, it remains flexible. Because it
is in the plastic family, powder continues to move with the metal as it
expands and contracts with the weather. Paint gets harder as the
chemicals that make it liquid evaporate. Once paint cures, it is more
likely to chip, crack and peel, allowing the metal underneath to rust.
Because of it’s plastic nature and flexibility powder bounces back
instead of chipping.
powder contains UV protectants that help maintain both color and gloss
throughout the years. While most paint begins to fade after 1-2 years,
powder will stay glossy for 10-15 years or more. We have attached a
picture of two trellises that were installed in mid 2007. One was
painted (not by Z shop) and is on the “protected” side of the building.
It receives morning sun. The other was powder coated (by Z shop) and
receives full afternoon sun. While the painted trellis is faded,
chipping and rusting, the powder coated trellis still looks as good as
day one. If you would like to see them, give us a call and we can tell
you where they are located.