By Michael Hornbaker, Loren Keene,
Randy Krawiec, Rob Tesmer,
and Todd Wilken
Almost all metal fabricators consider on- time part delivery a key metric. In today’s just-in-time manufacturing environment,
the parts need to be there so the customers don’t
miss a beat in their own manufacturing facilities.
To maintain their ability to get parts where they
need to be and when they need to be there, more
fabricators are investigating in-house finishing capabilities. ;ey know that once metal parts leave
the shop to receive a liquid or a powder coating,
they have lost their ability to guarantee a delivery
date. It is quite literally out of their hands.
Now, a finishing contractor may be a good supply chain partner, but a metal fabricator is one of
its many customers—perhaps one of the smaller
ones. If the custom coater needs to clear the production schedule for one of its largest customers,
guess where that leaves the small batch from the
Metal fabricators looking to take on finishing
should know about two of the most common finishing alternatives—liquid and powder coating—
and the requirements involved for a company hoping to apply one or both.
What Makes up the Coating?
Liquid. ;e basic raw materials comprising a liquid
coating are additives, carriers, pigments, and resins.
Additives make up the smallest portion of any liq-
uid coating composition, but they impart special
characteristics on the overall finish; for example,
they might assist with rust prevention or UV pro-
tection. ;e carrier is the main liquid used to for-
mulate the paint. ;e carrier can be water, solvent,
or a combination of the two. Liquid coatings heavy
in solvents traditionally have been the dominant
form of liquid finish applied to metal parts over
the years, but more interest has been directed to
waterborne and high-solids coatings, which release
a minimal amount of volatile organic compounds
(VOCs) during application when compared to tra-
ditional solventborne coatings. Pigments play a
role in final appearance and performance to some
extent. As a rule, the volume of pigments influ-
ences the gloss of the film. ;e more pigment pres-
ent, the lower the coating’s gloss. Resins act as the
base of the liquid coating. ;ey primarily govern
the overall performance of the coating, helping the
paint to excel for particular applications.
Powder. Powder coatings don’t require a carrier.
;e additives, pigments, and resins are formulated
in a powder form. To apply the material to parts,
the powder is electrostatically charged and conveyed via compressed air. ;e charged powder is
attracted to a grounded part. ;e part is then taken through an oven, where the heat changes the
powder from a solid to a liquid and then to a solid
coating. Generally, powders do not have any or extremely low VOCs.
How Does the Coating
Affect the Environment?
Liquid. Solventborne coatings are often specified
for a finish because of their dependable performance and ability to air-dry in a matter of minutes.
Unfortunately, most of the traditional liquid paint
formulations from yesteryear no longer are around
because of the need to reduce VOCs emitted during application.
;at has led to the development of more environmentally friendly coatings, such as new waterborne formulations and high-solids coatings, that
emit low VOCs. ;e waterbornes, which have come
a long way from the early versions used 15 years ago,
are slowly growing in acceptance. However, some
The basics of liquid and powder coatings
Taking on finishing in-house?
Get to know the coating technologies first