Nickel, alloys with copper

Watanabe and coworkers have found that alloy electrodes are often more efficient than electrodes made of pure metals. They have studies the reduction of CO on copper alloys with nickel, tin, lead, zinc cadmium and mercury [24]. The alloys were all produced by electroplating from mixtures of the metal ions in solution. In the cases of nickel, tin, lead and zinc alloys, current densities and faradaic efficiencies were all found to be greater than those of the pure components. Also product selectivity was found to be a function of the metal alloyed with copper. 

Monel, the classic nickel-copper alloy with the metals in the ratio 2 1, is probably, after the stainless steels, the most commonly used alloy for chemical plant. It is easily worked and has good mechanical properties up to 500°C. It is more expensive than stainless steel but is not susceptible to stress-corrosion cracking in chloride solutions. Monel has good resistance to dilute mineral acids and can be used in reducing conditions, where the stainless steels would be unsuitable. It may be used for equipment handling, alkalies, organic acids and salts, and sea water. 

The earliest of these, a chisel-shaped tool of about 3500 B. C., was of pure copper (99.9 per cent). So also a small figure of about 1300 B. C. was of pure copper. Some fifteen other articles, dating from 1900 B. C. to 350 B. C., were of copper alloyed with tin, ranging from 3 to 14 per cent tin, or with tin and lead, the lead ranging from small quantities, probably unintentional, up to 25 per cent. One figure, of 700 B. C., was of copper with 1.72 per cent arsenic. All of these bronzes contained small quantities of iron, and often small quantities of nickel, cobalt and arsenic, probably unintentional constituents. 

In the case of so-called active soldering an active solder is used a metallic solder containing interface active additives which make certain that the molten solder wets the ceramics. An example of such a solder is a silver / copper alloy with a titanium or titanium / indium additive which can be used when soldering zirconium (IV) oxide to certain steels, aluminium oxide to nickel / cobalt or iron / nickel alloys and aluminium oxide to a iron / nickel / cobalt alloy. 

In seawater, nickel shows a corrosion rate below 0.13mmyr and could be classified as corrosion resistant. In stagnant seawater, formation of a biofilm on the surface is possible and this could lead to microbiological-induced corrosion. In order to prevent this, nickel-copper alloys with 30% Cu are used, because copper has an antibacterial effect. 

Copper and some copper alloys do exhibit corrosion under advanced velocity conditions. Their corrosion resistance is dependent on the growth and maintenance of the protective layers formed on the metal surface. The maximum velocity recommended for copper in seawater is 0.9 m/sec. Alloying with nickel or aluminum increases the resistance of copper alloys to impingement attack [72,79]. 

The copper-nickels are single-phase solution alloys, with nickel as the principal alloying ingredient. The alloys most important for corrosion resistance are those containing 10 and 30% nickel. Table 18.11 lists these wrought alloys. Iron, manganese, silicon, and niobium may be added. Iron improves the impingement resistance of these alloys, if it is in solid solution. Iron present in small microprecipitates can be detrimental to corrosion resistance. To aid weldability, niobium is added. 

Mold makers should avoid material combinations of aluminum and copper alloys with a mutual temperature control circuit, unless the metallic cooling bore holes can be protected (e.g., by chemical nickel). Contact corrosion, which can develop by physical contact of aluminum and nobler metals (e.g., copper), can be prevented by electrically insulating separating agents or adhesive. 

Copper-nickels. These are alloys with nickel as the principal alloying element, with or without other elements designated commonly as nickel silvers (i.e., alloys containing zinc and nickel as the principal and secondary alloying elements). 

For example,copper has relatively good corrosion resistance under non-oxidizing conditions. It can be alloyed with zinc to yield a stronger material (brass), but with lowered corrosion resistance. Flowever, by alloying copper with a passivating metal such as nickel, both mechanical and corrosion properties are improved. Another important alloy is steel, which is an alloy between iron (>50%) and other alloying elements such as carbon. 

Nickel—Copper. In the soHd state, nickel and copper form a continuous soHd solution. The nickel-rich, nickel—copper alloys are characterized by a good compromise of strength and ductihty and are resistant to corrosion and stress corrosion ia many environments, ia particular water and seawater, nonoxidizing acids, neutral and alkaline salts, and alkaUes. These alloys are weldable and are characterized by elevated and high temperature mechanical properties for certain appHcations. The copper content ia these alloys also easure improved thermal coaductivity for heat exchange. MONEL alloy 400 is a typical nickel-rich, nickel—copper alloy ia which the nickel content is ca 66 wt %. MONEL alloy K-500 is essentially alloy 400 with small additions of aluminum and titanium. Aging of alloy K-500 results in very fine y -precipitates and increased strength (see also Copper alloys). 

Copper and nickel can be alloyed with zinc to form nickel silvers. Nickel silvers are ductile, easily formed and machined, have good corrosion resistance, can be worked to provide a range of mechanical properties, and have an attractive white color. These alloys are used for ornamental purposes, as sHverplated and uncoated tableware and flatware in the electrical iadustry as contacts, connections, and springs and as many formed and machined parts (see Electrical connectors). 

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