< ALUMINIUM BRONZE
COPPER/NICKEL (NICKEL BRONZE, CN SERIES, EN CC330-334G)
Copper/nickel casting alloys contain some 30% nickel, with further additions of either chromium (CN1) or niobium (CN2). The wrought versions of this material contain between 5% and 32% nickel together with various trace elements (NES 779 & NES 780 alloys). Casts formed in copper/nickels, like those in copper/aluminium alloys, are highly resistant to corrosion and typically specified for service in adverse conditions – most commonly as naval architecture. The main interest to artists again is the material’s distinctive colour – in this instance offering an appearance close to that of silver coinage (though a green tint is often discernable, especially after a period of out of doors exposure and weathering).
Nickel bronzes are difficult to patinate, structurally stronger and more problematic to cast and chase than most of the other cast copper alloys. Wrought material is available from specialist non-ferrous metal stockists – round bar (BS 2874), and sheet or plate (BS 2870), are the most common forms available. Cast and wrought nickel bronze alloy (90/10 grade CN 102/NES 779 is best overall for general purpose use), is usually welded by a TIG process, though filler wire for MIG process is also available (nickel rich copper filler material for welding carries a C17 or C19 designation). In keeping with other unusual or exotic alloys, founders are likely to charge premium rates for cast work in this material.
OTHER COPPER ALLOYS
A number of other copper based alloys are available including copper/chromium (BS 4577/EN CC040&140A), copper/manganese/aluminium (EN CC212E) and copper/beryllium (CB101 wrought alloy). However, these are normally used in highly specialised industrial applications and are of little interest to the artist or designer except perhaps on a conceptual level. The casual use of copper/beryllium materials should be avoided, this material can release a highly toxic particulate if abrasively worked.
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