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About Aluminum Anodizing
Aluminum anodizing is a unique electrochemical process
that increases the thickness of a passive, naturally occurring, protective
aluminum oxide film. The resulting finish, depending on the process,
is the second hardest substance known on earth next to a diamond, and
is often comparable to sapphire. Metal anodizing expands on the natural
oxidation process by adding electricity and chemicals to create a hard,
transparent surface to the aluminum. Without this process, regular aluminum
will corrode and become weak, but anodizing provides protection from
these defects. After anodizing, the metal becomes hard and weather-resistant.
Other metals, such as titanium,
can be anodized to produce similar results.
Before starting the anodizing process, the metal must be clean to prevent surface
problems. Next, the metal is pre-treated with a bath to produce various degrees
of shininess. Several of these methods are bright dip anodizing, satin anodizing
and matte anodizing. Now the product is ready to be anodized, and in this step
it is coated using a variety of methods, including hard coat, standard sulfuric
and color
anodizing. After this, the product is covered with color dye or a sealant.. Anodizing is
a relatively short process that only takes a few hours to complete.
Anodized aluminum is known for its excellent corrosion resistance. Color variation
is also possible. The anodized finish is porous enough to accept penetration
by color dyes. After dyeing, the color is fixed by sealing in a hot nickel acetate
or equivalent solution. Since anodized aluminum is inorganic, it is therefore
unaffected by ultraviolet rays. Another benefit of aluminum anodizing is the
possibility of future repair or re-coloring by stripping the anodized layer from
the aluminum. Additionally, the anodized surface does not flake and is both insulative
and static-resistant.
Several different methods of aluminum anodizing are available. One of these
is hard
coat anodizing, which is useful because it is non-conductive to electricity
and also has better wear resistance than other methods. Standard anodizing is
another method that provides a great base for bonding to other metals and organic
coatings. Many products are made with anodized aluminum, including refrigerators,
dryers, mailboxes, duct covers, grills, pots, pans, bicycle frames, wheel covers
and electronic products like clocks. The architectural industry is very dependent
on the production of quality anodized aluminum, as it is often used for framing
of buildings. Other industries that benefit from the use of anodizing are the
automotive, military, aerospace, medical and industrial industries.
Featured
Articles
http://www.nomma.org/support/finishing/Anodizing/anodizing.html
http://www.byv.kth.se/avd/byte/bphys/pdf/art_0103.pdf
Types of Aluminum Anodizing
- is
a technique used to coat the exterior of a metal with a protective film.
- is a process through which the surface of
an anodized coated with a protective black dye.
- refers
to the pretreatment step before anodizing, which takes place in a bath of
acids and creates a bright, shiny finish.
- is
a process that provides corrosion resistance and makes the aluminum
surface electrically conductive. It also provides a superior surface
condition for the application of paints, powder coats and adhesives.
- preoxidizes
the aluminum surface for a clear, uniform finish.
- is when a colored coat is applied to the exterior
of a metal.
- provides a thin coating of aluminum oxide that is
tightly bonded to the surface of the aluminum. This method offers
corrosion resistance and aesthetic appeal, as well as makes the aluminum
surface electrically non-conductive.
- is a variant of
anodizing. It produces similar results to standard anodized
surfaces, but the thicker and denser hard anodic film limits the
coloring results to dark tones.
- is
the filling of internal cracks, voids and corroded pockets, which would
otherwise cause castings, forgings and powdered metal parts to leak.
- is used most often in the jewelry segment
of the industry, as it has less occurrence of skin allergy than
any other metals.
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