What is anodizing?
Anodizing is an electrochemical process that thickens and toughens the protective Aluminum Oxide. The resulting finish, depending on the process, is the hardest substance known second only to diamond. The anodic coating is part of the metal, but has a porous structure that allows secondary infusions, (i.e. organic and inorganic coloring, lubricity acids, etc.) The anodizing process is non-hazardous and produces no harmful or dangerous by-products. Anodizing is a safe process that is not harmful to human health.
How closely can the thickness of Hard Anodizing be controlled for a coating thickness requirement of .002 mils.
In production, plus or minus .0002 can be maintained. Closer control is possible but cost is significantly higher.
How much buildup will there be on a .002 Hard Anodize coating thickness?
A coating thickness of .002 will increase the thickness on one side of a flat surface by only.001. This being true, the increase in measurement of a rounded surface that is hard anodized at .002 mil coating thickness would be a total change of plus .002 mils in diameter.
How much buildup can be expected on a decorative sulfuric acid anodized .0006-co thickness?
Approximately .0002 buildup per surface can be expected on a sulfuric acid decorative coating with a coating thickness of .0006. The lower current density applied and higher temperature used during processing lend itself to lower efficiency and subsequently less buildup per surface than the Hard Anodizing Process.
What about buildup allowances for threads that need to be coated?
Threaded areas are tricky in Hard Anodizing. The increase in pitch diameter is at a ratio of 4 to 1 in hard anodizing. This must be taken into acocunt when designing threaded parts. When extremely tight thread specifications are involved, it is often necessary to mask the threads. Samples should be processed if your outcome is in doubt.
How uniform can I expect the coating when applied to blind bore holes?
Small diameter bores with a depth > three (3) times the diameter are partially shielded the current. Consequently, they will not build up a uniform coating unless internal cathodes are used. This application is expensive and should be avoided when possible.
Why is it important to know the aluminum alloy that is being processed?
Aluminum alloy identification is a must for the anodizers to do their job effectively. Hard Anodize in particular, has a greater buildup per surface than decorative anodizing and alloy thickness differences are magnified when processing unknown aluminum alloy. For instance, an aluminum alloy processed unknowingly with a 2024 alloy can produce significant buildup difference and also greatly increase the danger of burning.
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