Metal finishing Q&As since 1989

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Copper Anodized Aluminum

 

I have a 3-part question, with each question leading into the next:

1. Can you anodize aluminum with copper?

2. If so, is it economically cheaper than using solid copper?

3. Finally, in-the-long-run will copper anodized aluminum hold up better to the elements or will solid copper hold up better?

I know that from a decorative standpoint weathered copper is prettier with its green patina. But I am wondering if the same effect can be obtained at a reduced cost. Aluminum is less expensive than copper, and if it can be anodized, than maybe the same effect (the green patina) would still be obtainable at a reduced cost per. sq. foot. But if there is increased maintenance costs than this whole question might be moot. Any guidance here would be greatly appreciated.

Steven Valley
- Falls Church, Virginia, USA

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1. No, but you have some terms mixed up. You can electroplate aluminum with copper.

2. Sometimes. A lot of bus bar and wire is copper plated aluminum.

3. Solid copper will hold up better. The 'risk factor' for copper plated aluminum may be more than you are interested in, because it is possible that the items will be poorly plated.

Before asking any followup questions, Steve, please fill us in on the real-world situation; Thanks.

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

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You can anodise aluminium and do one of the following:
(1) dye impregnate the anodised layer (standard colouring method).
(2) Electrophoretically impregnate an unsealed anodised layer with copper sol and then chemically treat to achieve the green patina.
(3)Copper flash onto unsealed anodised aluminium and then chemically treat to achieve the green patina.

John Tuohy
- Ireland

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I stand corrected then, John. Can you refer me to any article on this technology of making a patinable aluminum article? It sounds interesting for rain gutters, etc.

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

My shop does anodizing & we have done anodize dyed to match copper & it looks great - lasts long & doesn't tarnish like copper.

David A. Kraft
- Long Island City, New York
 

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Ted,

I'm a chemical engineer by qualification and aerospace/automotive/pharmaceutical by professions. I must admit ignorance to most commercial metal finishing titles and frankly a bit humbled by the sort of blase esoteric knowledge displayed by the professionals on this website. Please don't think me arrogant but I do like to keep the plug&play professionals on their toes.

Section (2): Patent by Japanese researchers. Development results were good. NASA played with gold versions for infrared mirrors. I don't know the commercial stage but that was years ago. I'll have a search for the reference. Section (3): Work done by myself for Rolls Royce ~1989. Technically not difficult. Anodised layer must be between 5um and 10um. Current density close to 'burning' point. Fast transfer and 5% nitric dip to avoid hydroxide gel in pores. DI rinse and electroless copper by reduction. Colouration by 45 degC humid HCl fumes. 30min bake at 95 degC. Fast IPA rinse and force dry. Acrylic lacquer seal.

Commercial process..I'll have a dig about.
Proprietary breach..possibly partial!

John Tuphy
- Ireland