What is Anodized Aluminum?

manufacturing industry

Many metals are structurally weakened by the oxidation process, but not aluminum. Aluminum can actually be made stronger and more durable through a process called 'anodizing'. Anodizing involves placing a sheet of aluminum into a chemical acid bath, quite often acetone in laboratory experiments. The sheet of aluminum becomes the positive anode of a chemical battery and the acid bath becomes the negative. An electric current passes through the acid, causing the surface of the aluminum to oxidize (essentially rust). The oxidized aluminum forms a strong coating as it replaces the original aluminum on the surface. The result is an extremely hard substance called anodized aluminum.

Anodized aluminum can be nearly as hard as diamond under the right anodizing process. Many modern buildings use anodized aluminum in places where the metal framework is exposed to the elements. Anodized aluminum is also a popular material for making high-end cookware such as frying pans and pots. Heat is distributed evenly across anodized aluminum, and the process of anodizing provides a naturally protective finish. It is possible to use another electroplating process to make anodized aluminum look like copper or brass or other metals. Special dyes can also be used to color the anodized aluminum for decorative uses.

Because of its strength and durability, anodized aluminum is also used in a number of other applications. Many of the satellites circling the Earth are protected from space debris by layers of anodized aluminum. The automobile industry relies heavily on anodized aluminum for trims and protective housings for exposed parts. Furniture designers often use anodized aluminum as the framework for outdoor pieces as well as the base metal for lamps and other decorative items. Modern home appliances and computer systems may utilize anodized aluminum as protective housing.

Anodized aluminum may not be appropriate for all applications because of its non-conductive nature. Unlike other metals such as iron, the oxidation process doesn't seem to weaken aluminum. The layer of 'aluminum rust' is still part of the original aluminum and will not transfer to food or easily flake off under stress. This makes it especially popular for food-service applications and industrial applications where durability is crucial.

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Posted by: YalieBabie
What is the distinctive molecular basis for this advantagious oxidation of aluminum, as a opposed to other metals which are degraded by rusting?
Posted by: anon933
If i was to place aluminum that is anodized to 25 microns attached to brass stands into a fountain that contains bromide is there any way to stop corrosion?
Posted by: anon1849
Our company is using anodized aluminum reflector for our lighting fixtures. Would it be better to use a vaccum metalized galvanized iron sheet instead. What are the short term and long term advantage or disadvantages in using the latter. Thanks
Posted by: anon3855
"chemical acid bath, quite often acetone" Acetone is not an acid, and will not promote anodizing as described. It is a ketone, and if it is used in the anodizing process at all it is for degreasing.
Posted by: dsmith
A question concerning anodized aluminum (6061-T6)as a housing for a 303 stainless steel, spring loaded plunger pin (.25" diam). Would I have an issue with wear or corrosion if I used this combination? The pin has about .38" lng min in the alum housing & travels about .25" (low cycles, occasional, moderate side load on extended pin). I know it's not the total picture, but would appreciate any feed back.
Posted by: gloriaclary
Why aren't pots and pans made of hard anodized aluminum dishwasher safe?

Posted by: anon8706
Acetone is actually a ketone. Ketone is just a general label for several chemicals.
Posted by: anon9063
lots of sites for anodizing talk about aluminum, but what about stainless steel or other types of metals. on many cheap consumer products like "non-load bearing" carbeiners the anodizing layer comes off with a mere scratch, but other things nothing short

of a grinder would leave a mark... someone enlighten me please, thanx

Posted by: JB757
How well will anodized alum. pipe stand up when used in the marine industry (yachts)as a thru hull penetration for raw salt water intake and or sewage systems. How does the material effect the surrounding alum. that is not anodized in a constant saltwater enviroment. does it not cause an electrolosis problem between the two due to the electric charge that some anodized alum. materials retain.

JB


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Source: Aluminum Anodizers Council

Written by Michael Pollick

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