Copper content in Marine Aluminum Electrical Fittings

[KenAlmon]

I have read in many suppliers sites/catalogues about the role copper plays in aluminum electrical equipment. Most of the time, manufacturers take great pride in identifying that they have no more than 0.1%, 0.4% or 1.5% copper in their aluminum products (typically cast, not forged). Can you please advise what % is the best in so far as application in a marine (salt spray) environment is concerned? I am sure that someone did a study at one point and identified that for increasing copper content in a marine environment, more pitting occurred as a result of increasing copper. Do you know where I may find the results of such a study? Finally, how does one ensure low copper content? Is it separated during casting or before that?

Thanks

Ken Almon

 

[mcguire]

The Metals Handbook states that any copper above "a few tenths of a percent" causes the problem which is a dissolution and redeposition of copper causing galvanic couples. 3003 with 0.2% max or 5xxx grades with 0.1% max ought to be fine, or as good as you'll get if you have to use aluminum.