Metal finishing Q&As since 1989

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Coating on Aluminum for Electrical Insulation

Can I dip my aluminum discs in some kind of conversion coating bath and expect a thicker oxide layer to have grown and withstand higher voltages?

Does anyone know what happens if I boil my aluminum in deionized water and get some kind of boehmite layer?

Jose Carlos
transducer manufacturer - around Boston
2005

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In general, conversion coatings are used on aluminum when conductivity is to be maintained, and anodizing is done when insulative value is sought. Is there a reason they can't be anodized? sulfuric acid anodizing is the most common and probably the least expensive for this purpose, but boric acid anodizing is used for electrolytic capacitors and may suit your needs.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

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Hello,

According to Wernick, Pinner, and Sheasby, you can get a thin but highly protective coating by boiling aluminum for 20 hours in distilled water. The coating itself would be non-conductive as well as protective, but whether or not it would be thick enough to prevent your voltages from breaking through (this would also be affected by the pressure exerted by your contacts as well) would have to be determined.

As a manufacturer though - definitely take Ted's advice! The boiling water would probably end up being more expensive, and you couldn't be as certain of the quality. Anodizing would be the way to go. Good luck.

Jim Gorsich
Compton, California, USA
2005