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I am about to install a copper weathervane which will also work as lightning conductor (it will be mounted on top of an earthed aluminium flagpole).

Because:

  • exposed to weather, copper will corrode and become looking like the Statue of Liberty; and
  • I want the weathervane to look white/silver/metallic

— I am looking for options to coat the weathervane with conductive metallic layer which will:

  1. Protect copper from corrosion
  2. Be electrically conductive
  3. Look white/silver/metallic

Products like EMI/RFI shielding would perhaps be ideal for the purpose, but the problem is that they are not available in New Zealand, and they are classified as dangerous goods to be shipped here by ordinary mail (except for water based, but this won't be weather resistant).

I am therefore looking at making conductive coat myself from aluminium powder.

What kind of base/resin should I use?

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    According to the dissimilar metal charts I have seen, and in real world experience, aluminum and copper do not get along at all. Copper will cause the aluminum to oxidize in short order. – Jack Jun 26 '18 at 5:32
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You are way overthinking this. First, ever hear of companies doing chrome plating? Yes. Zinc plating (galvanizing)? Yes. Aluminum plating? No. And there's a reason for that! Aluminum corrodes horribly in the weather, it would be somewhat less desirable than manure plating.

Just buy cold galvanizing compound. It is paint that's over 90% zinc, designed to repair/restore things which were galvanized. The remaining 10% is the resin that holds the paint together, and the solvents which evaporate.

It weathers to the appearance of a galvanized tin roof.

The solids are heavy and really want to separate. It takes a long time to stir it up. It wants to separate in the paint cup while you are painting, so you must constantly stir it up from the bottom. Also, it's liable to break a paint shaker unless the shaker is designed for much larger cans.

Seriously, the can is so heavy you want to heat it up to see if it says "One ring to rule them all".

If you must make your own paint, don't use epoxy as a base. Sunlight destroys epoxy. But there are several other things like epoxy which don't have that problem, and they are widely used by shops that make skateboards and surfboards. An example is polyurethane, which comes in 2 parts, you mix it like epoxy, mix in your powdered metal base, and off you go.

Also before you say "not available in NZ", do make sure you've done some genuine detective work. Industrial procurement is never easy. I need a custom crankshaft for an obsolete industrial diesel, they don't sell those at Walmart and it isn't on the Internet. You have to dig, dig, dig through the industrial supply network.

  • Aluminium will be just fine when not in contact with soil/alkali — the surface oxide layer prevents corrosion. The reason aluminium plating does not exist is different: aluminium is too active to be reduced from water solution — it will react with water immediately as no protective oxide layer will be formed. Thanks for the hints re cold galvanizing compound and polyurethane base. – Greendrake Jun 26 '18 at 4:57
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If you want another alternative to painting and the copper is bright and brand new. On top of that it has no existing soldered joints, you could apply soldering flux over the whole thing and melt a coat of lead or solder over it with a torch and bar solder You may be able to find solid lead bars too, they have a lower melting point than 50-50 solder

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About any "silver" colored paint contains aluminum flake as pigment and would satisfy your requirements. You are making it too complicated.

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