Alloy copper

Copper is used in three basic forms pure, alloyed with zinc (brass), and alloyed with tin (bronze). Copper has a tendency to form brittle amine 

While contact between aluminium alloys and copper and cuprous alloys (bronze, brass) causes no appreciable galvanic corrosion of aluminium under atmospheric conditions, it is nevertheless advisable to provide insulation between the two metals to localise surface corrosion of the aluminium. 

It should be recalled that the corrosion product of copper, verdigris, attacks aluminium and may be reduced under the formation of small copper particles. These particles in turn cause localised pitting corrosion of aluminium. 

Like copper salts, mercury salts lead to severe pitting corrosion of aluminium. 

Due to its volatility, mercury can easily be transported by moving fluids such as natural gas that contains minute traces [8]. Experience shows that mercury may be concentrated in plants where natural gas undergoes liquefaction and regasification it may damage aluminium heat exchangers [9]. For this reason, mercury is trapped in specific devices. 

Mercury itself leads to severe corrosion of aluminium, which appears as very narrow white lines, possibly thicker than 1 cm. It may also lead to intercrystaUine corrosion and rupture at cracks [10]. 

Since before the dawn of history, when primative people first discovered the red metal, copper has been serving us. The craftsmen who built the Great Pyramid for the Egyptian Pharaoh Cheops used copper pipe to convey water to the royal bath. A remnant of this pipe was unearthed some years ago, still in usable condition, a testimonial to copper s durability and resistance to corrosion. Today, nearly 5000 years after Cheops, copper is still used to convey water and is a prime material for this purpose. 

Copper ores foimd in the United States contain approximately 1% copper in the form of copper sulfide. Copper sulfide concentrates are smelted to yield a matte that is a mixture of copper and iron sulfides. These mattes are remelted in a converter where air is blown through the mattes to oxidize the remaining sulfur. The remaining copper is approximately 99% pure. This is referred to as blister copper and is further refined to remove other impurities. The final tough-pitch copper has a purity of about 99.5%, which is suitable for many alloys. A higher purity of 99.9% can be obtained by electrolytic refinement of the tough-pitch copper. 

This designation system is used throughout America, Australia, and Brazil. Each number refers to a specific alloy composition. The UNS numbers for specific groups of wrought alloys are given in Table 18.1 along with applications for each group. 

There are more than 100 temper designations for copper and copper alloys. These may be found in ASTM B601, Standard Practice for Temper 

Unified Numbering System for Wrought Copper and Copper Alloys 

High conductivity of electrical grades superior to aU other metals except silver on a volume basis and aluminum on weight basis. High cost relative to other common metals. 

High thermal conductivity. Conductivity reduced by small quantities of other elements. 

Excellent ductility permits easy working. High casting temperatures of the metal and its alloys. 

Mechanical properties of copper strength,. creep resistance, and fatigue performance are improved by alloying (but conductivity is impaired) The gasing reaction of copper with oxygen requires precautions when temperatures exceed 700°C. 

Good corrosion resistance to potable water and to atmospheric and marine environments can be further improved by alloying. Toxic therefore must not be used in contact with foodstuff (e.g., food processing plant). 

Halogens under specific conditions— for example, fluorine below about 400 C, dry HF below 600°C, dry CI2 below 150°C, dry Brj at 25°C, iodine below 375X [16], 

Oxidizing acids, for example, HNO3, hot concentrated H2SO4, and aerated nonoxidizing acids (including carbonic acid). 

NH4OH (plus O2). A complex ion, Cu(NH3) +, forms. Substituted NH3 compounds (amines) are also corrosive. These compounds are those that cause stress-corrosion cracking of susceptible copper alloys. 

High-velocity aerated waters and aqueous solutions. In corrosive waters (high in O2 and CO2, low in Ca and Mg ), the velocity should be kept [8,13] below 1.2 m/s (4ft/s) in less corrosive waters, 65 C ( 150 F), the velocity should be kept below 2.4 m/s (8ft/s). 

Hydrogen sulfide, sulfur, and some sulfur compounds. 

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The electrical industry is one of the greatest users of copper. Iron s alloys -- brass and bronze --are very important all American coins are copper alloys and gun metals also contain copper. 

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