Environmental Engineering Reference
In-Depth Information
Table 4.3
Some common copper alloys and their nominal chemical
composition
Material
Composition (%)
Beryllium copper
98 Cu, 1.9 Be, 0.2 Ni or Co
Red brass
85 Cu, 15 Zn
Cartridge brass (yellow brass)
70 Cu, 30 Zn
Admiralty brass
71 Cu, 28 Zn, 1 Sn, 0.04 As
Aluminum brass
77 Cu, 21 Zn, 2 Al, 0.04 As
Muntz metal
60 Cu, 40 Zn
Phosphor bronze
90-95 Cu, 5-10 Zn, 0.25 P
Aluminum bronze
92 Cu, 8 Al
Cupronickels
69-88 Cu, 10-30 Ni, 0.5-1 Fe, 0.5
Mn
Nickel silver
65 Cu, 25 Zn, 10 Ni
Source
: Adapted from: M. G. Fontana,
Corrosion Engineering
, 3rd ed., McGraw-Hill, New
York, 1983.
5-10% tin, often with addition of a small amount of phosphorus. They are more
resistant to SCC and impingement attack than brasses. Aluminum bronzes with
5-8% aluminum and cupronickels containing 10-30% nickel with small iron
additions have superior resistance to erosion corrosion. Copper alloys are used
extensively as heat exchanger tubes because of their high thermal conductivity,
and resistance to erosion corrosion is an important consideration in such applica-
tions. Copper alloys are also used for piping, valves, pumps, gears, bushings,
shafts, tanks, and other vessels.
4.1.6 Nickel and Its Alloys
Nickel is inherently resistant to caustic solutions at all concentrations and temper-
atures, seawater, and slightly acidic solutions. Addition of nickel to cast irons,
steels, and stainless steels improves the corrosion performance of these alloys.
However, nickel is not resistant to strongly oxidizing solutions, e.g., nitric acid
and ammonia solutions. At high temperatures, nickel is attacked by sulfur-bearing
gases and is embrittled.
Nickel alloys constitute a major group of corrosion-resistant alloys. Some im-
portant nickel alloys are listed in Table 4.4. Monel, containing about 30% copper,
is considered to be a natural for handling hydrofluoric acid. A host of alloys have
been developed with chromium and molybdenum as principal alloying elements.
Chromium addition induces passivity and improves corrosion resistance in oxi-
dizing solutions, including nitric acid. Nickel-chromium-molybdenum alloys
(Hastelloy) are best suited to handle hydrochloric acid at all concentrations.
