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Pub 223 - Copper for Contacts

This publication looks at the properties required for contact materials, and to identify those applications in which copper or copper alloys have special advantages. 1980, revised 2015. 36pp.

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Can copper and copper alloys be hardened by heat treatment?

Some alloys can, including copper-beryllium, copper-chromium and copper-nickel-silicon. Most unalloyed coppers and brasses can only be softened by heating.

Can copper-nickels be brazed?

Yes they can be brazed by all processes. Appropriate silver brazing alloys should be used as phosphorus bearing brazing alloys cause a reaction with nickel to form a brittle phosphide phase.

Can copper-nickels be welded directly to steel?

Yes they can using appropriate 65% nickel-copper consumables to avoid iron dilution effects.

How many copper alloys are available for aquaculture so far?

Three. They are: Copper-Zinc, Copper-Nickel, and Copper-Silicon.

The Corrosion Performance of Metals for the Marine Environment: A Basic Guide (European Federation of Corrosion (EFC) Series)

This book, edited by Carol Powell and Roger Francis, is aimed at engineers new to the marine environment and those wanting to update their knowledge. Applications, commonly used alloy compositions, mechanical properties and the types of corrosion that the alloy groups are susceptible to are all described. The concluding section provides an explanation of galvanic corrosion in seawater and how each alloy group behaves when coupled to others

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Which copper alloys are currently available for aquaculture and do they have different applications?

Three alloys are currently commercially available: copper-zinc, copper-nickel and copper-silicon.

Copper-zinc is good for flexible mesh containment systems.
Copper-nickel is good for rigid (e.g. welded) mesh.
Copper-silicon is good where rigid mesh is needed, or where panels can have flexible connections.

How much silver is present in nickel silvers?

None, nickel silvers are copper-nickel-zinc alloys which have an attractive colour when polished.

What situation is each best for?

Copper-Zinc is good for flexible mesh containment systems.

Copper-Nickel is good for rigid (e.g. welded) mesh.

Copper-Silicon is good where rigid mesh is needed, or where panels can have flexible connections.

What are the critical pitting and crevice corrosion temperatures for copper-nickels in chloride environments?

Copper-nickels do not behave in the same way as stainless steels do towards corrosion by chlorides and these parameters are not appropriate to them. They do not have a critical temperature limit.

What types of corrosion are copper-nickels sensitive to?

It is important that maximum velocity guidelines are adhered to for piping and heat exchanger/condenser service, as high velocities can cause impingement attack. Exposure to sulphides and ammonia in polluted seawater can lead to pitting or high corrosion rates and it is important to avoid these conditions, particularly during commissioning, start up and standby.