Resource Library

I intend to use copper as a cladding material but I do not want to wait for the natural patina to form. What do you suggest that I might use?

Copper sheet is available in pre-patinated form.  As well as green, other attractive colours such as brown, gold and silver are available.  See www.kme.com and www.aurubis.co.uk.
What effect does heavy cold working have on the electrical conductivity of copper?

It reduces by about 3%.
I require an aluminium bronze with a very low iron content (0.5-0.7%). The application is a holder in an induction furnace. It is important that the holder does not become heated in service.

Suggest DEF STAN 02-834, which is a naval grade of aluminium bronze with a low magnetic permeability.  This meets MOD requirements.
Which copper alloy has the best corrosion resistance in seawater?

Various copper alloys have particular strengths under specific sea water conditions but on balance 90-10 copper-nickel has excellent corrosion resistance in many applications and is perhaps the most versatile. There is a detailed description of the properties and applications of this and other popular copper nickel alloys on the www.coppernickel.org website. Of course, aluminium bronze alloys, particularly nickel aluminium bronze, are also recognised for their corrosion resistance in severe seawater conditions and for that reason also have established applications as propellers and pumps and valves.
I wish to produce components by carrying out simple forming operations on brass sheet. Should I use the 70/30 Cartridge Brass (CW505L)?

CW505L is the most ductile brass, but for simple forming the more economical 63/37 Common Brass (CW508L) should be used.
Which copper alloy has the highest ductility?

70/30 brasses CZ106 (CW505L).
I wish to restore a copper canopy on an old building to its original condition. How can I do this?

Stages:

(a) Remove surface oxide with dilute (10%) hydrochloric acid
(b) Neutralise with bicarbonate solution (lye)
(c) Seal by chromate conversion
(d) Lacquer
(e) Wax
(f) Clean with detergent annually.
How does the surface of copper alloys change in seawater?

After exposure to seawater, copper alloys develop a surface oxide film which provides protection from corrosion.
Which copper alloys are strongest?

Copper-beryllium alloys.
I wish to restore the brass cladding on a shop front. Over a long period of time the brass has tarnished.

The first job is to clean the surface. Use a detergent with a kitchen scouring sponge (usually green). For a badly stained surface it may be necessary to incorporate pumice powder with the detergent .For large areas it may even be necessary to shot blast the surface. After cleaning dry the surface with hot air and as soon as possible wax the surface using natural wax. Natural wax is essential since it will enhance the true colour and form a protective coating, repelling water. Artificial wax should not be used since it will crack in time and draw water in.
What is 'INCRALAC'?

A clear acrylic resin finish containing tarnish inhibitor. It is an air drying ester lacquer containing Benzotriazole, a corrosion inhibitor. It can be relied upon to provide protection for 3-8 years outdoors and for much longer indoors .
Which copper alloys may be used for the design of springs?

Copper strip and wire may be produced with a combination of high elastic limit and good corrosion resistance, making them an ideal choice for springs. The main groups of alloys are:

  • Phosphor bronze, typically CW451K (PB102) with a yield strength of about 500N/mm2.
  • Nickel silver, typically CW409J (NS106).This is silver coloured and has excellent tarnish resistance.
  • Copper beryllium CW100C (CB101). This alloy is used where very high yield strength is required (greater than 1000N/mm2). These alloys are expensive and phosphor bronze will be adequate for most engineering applications.

A useful Specification is BS EN 1654:1998 (Copper and copper alloys. Strip for springs and connectors).