Electrolusis shouldn't be created with the copper napthante treatment to copper tubing, it's a great look as well.

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Alter Eagle Construction & Design

..typed that a Little fast. (spelling)

electrolysis & copper naphthenate

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Alter Eagle Construction & Design

Apart from the dielectric union that can occur between dis-similar metals, you have additional code compliance concerns when using any type of baluster to make sure it meets your lcoal minimum code requirement for lateral load.

Most codes require that any balutser be able to resist a load of at least 50lbs per sf from any lateral force.

Whether or not you can use the copper you suggest and on what spacing will be a matter of your lcoal code....and may not be permitted at all depending upon the loads...

You could use a dielectric union, the plastic spacers used in a common brand of aluminium deck balusters may be enough to seperate the two metals?

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Alter Eagle Construction & Design

couldn't you get the aluminum parts powder coated with 'clear', thus sealing them from the elements? this should eliminate any concerns about the chemical reaction between different metals.

powder coat is tough as nails, and i would think in this situation it would work rather well, providing the cost isn't overboard.