Anodizing is a process for producing decorative
and protective films on articles made from aluminum and its alloys.
The resulting oxide film improves both corrosion and abrasion resistance,
and is electrically inert. The porous nature of the film allows
production of colored coatings by absorption of organic dyes or
metallic pigments.
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Aluminum is the only metal that can be anodized
using standard anodizing procedures. If an aluminum component has
other metals attached, such as steel studs, pems, or heli-coils,
these areas must be masked prior to anodizing.
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A normal film thickness of .0006 inches will
prevent atmospheric corrosion for a minimum of ten years in a heavy
industrial environment. The oxide film itself is very hard, but
is generally too thin to increase the effective hardness of the
metal itself. It will, however, resist surface scratches and thus
protects the appearance of the metal under normal wear conditions.
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Following the dying of an anodized surface,
a sealer is applied to effectively close the pores and prevent fading,
staining, or bleeding out of color. A properly dyed and sealed component
will not fade under outdoor conditions for a minimum of five years.
Because the anodic film is molecularly bonded to the sub-strate,
and this film absorbs the pigment to the depth of the coating, the
colors will not chip or rub off.
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The anodic film is brittle, much like ceramic,
and will crack if bent. For this reason, all forming should be done
prior to anodizing. If certain areas are required to be un-anodized,
these areas can be masked prior to anodizing, or machined (normally
ground with an abrasive) following the anodizing process.
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This is a process similar to conventional anodizing,
in which a higher voltage is applied and which produces film thicknesses
in the range of .001 to .003 inches. This film provides greater
abrasion and corrosion resistance than conventional anodizing, and
is used to coat aluminum components that will be exposed to extreme
wear conditions.
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Compared to other types of electro-plating such
as chrome, cadmium, nickel, etc., anodizing is relatively cheap.
Pricing is based on surface area, weight, special handling requirements,
labor requirements for racking, or a combination of these. Call,
fax, or email your information, drawings, or blueprints for same-day
quotes.
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For color requirements not available in anodizing
dyes, painting is sometimes necessary. Anodizing provides an excellent
primer base for paint applications. Anodized surfaces can also be
silkscreened, dry-lube painted or powdercoated. For painting applications,
it is recommended that the anodizing not be sealed.
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Chem film, or chromate conversion coating, is
a dip process for coating aluminum with a chromium-based compound.
It offers excellent atmospheric corrosion resistance and is also
an excellent primer coat for paint or other organic coatings. It
is thinner than anodic coatings and is hardly competitive with anodizing
for abrasion and wear resistance. Chemical films are also electrically
conductive, unlike anodizing.
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Chromate (chem. film) coatings can be done
in either clear or yellow. These coatings can be dyed, but due to
the nature of the film, this is not recommended. The dyes are easily
scratched or rubbed off. Trivalent chromate films (RoHS compliant)
currently can be done only in clear, but work is being done to develop
a yellow color for that as well.
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