Copper content

The lead—copper phase diagram (1) is shown in Figure 9. Copper is an alloying element as well as an impurity in lead. The lead—copper system has a eutectic point at 0.06% copper and 326°C. In lead refining, the copper content can thus be reduced to about 0.08% merely by cooling. Further refining requites chemical treatment. The solubiUty of copper in lead decreases to about 0.005% at 0°C. 

Only lead alloys containing copper below 0.08% have practical appHcations. Lead sheet, pipe, cable sheathing, wine, and fabricated products are produced from lead—copper alloys having copper contents near the eutectic composition. Lead—copper alloys in the range 0.03—0.08 wt % copper are covered by many specifications ASTM B29-92 (7), QQL 171 (United States), BS 334, HP2 Type 11 (Canada), DIN 1719 (Germany), and AS 1812 (Austraha). 

The matte can be treated in different ways, depending on the copper content and on the desired product. In some cases, the copper content of the Bessemer matte is low enough to allow the material to be cast directly into sulfide anodes for electrolytic refining. Usually it is necessary first to separate the nickel and copper sulfides. The copper—nickel matte is cooled slowly for ca 4 d to faciUtate grain growth of mineral crystals of copper sulfide, nickel—sulfide, and a nickel—copper alloy. This matte is pulverized, the nickel and copper sulfides isolated by flotation, and the alloy extracted magnetically and refined electrolyticaHy. The nickel sulfide is cast into anodes for electrolysis or, more commonly, is roasted to nickel oxide and further reduced to metal for refining by electrolysis or by the carbonyl method. Alternatively, the nickel sulfide may be roasted to provide a nickel oxide sinter that is suitable for direct use by the steel industry. 

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). 

Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

For most commercial appHcations, a copper content in the range of 0.25 to 0.75% does not adversely affect the serviceabiUty of die castings and should not serve as a basis for rejection ASTM B 240-79 (93). 

Because the solution is capable of absorbing one mole of carbon monoxide per mole of cuprous ion, it is desirable to maximize the copper content of the solution. The ammonia not only complexes with the cuprous ion to permit absorption but also increases the copper solubiUty and thereby permits an even greater carbon monoxide absorption capacity. The ammonia concentration is set by a balance between ammonia vapor pressure and solution acidity. Weak organic acids, eg, formic, acetic, and carbonic acid, are used because they are relatively noncorrosive and inexpensive. A typical formic acid... 

Almost two-thirds of the world s copper resources are porphyry deposits. The term porphyry is generally appUed to a type of disseminated copper deposit that is hydrothermal in origin and characterized by a large proportion of minerals uniformly distributed as disseminations or in fractures and small veins. Copper contents are generally 1% or less. The most extensive porphyry deposits are located in western Canada, the southwestern United States, Mexico, and western South America. In addition to the porphyrys, there are large bedded copper deposits in Germany, Poland, the CIS, AustraUa, and central Africa. 

In spite of low copper contents, massive horizontal development renders porphyry deposits amenable to large-scale production methods. Porphyry deposits are associated with igneous activity and intmsion of molten rocks into cooler parts of the earth s cmst, often in connection with the formation of mountains. Erosion of mountainous areas exposes these deposits to weathering, and, under the right conditions, enables the formation of oxidized or secondary copper deposits. Copper mines in the United States are Usted in Table 2. 

Although some changes occur in the melting furnace, cathode impurities are usually reflected directly in the final quaUty of electrorefined copper. It is commonly accepted that armealabiUty of copper is unfavorably affected by teUurium, selenium, bismuth, antimony, and arsenic, in decreasing order of adverse effect. Silver in cathodes represents a nonrecoverable loss of silver to the refiner. If the copper content of electrolyte is maintained at the normal level of 40—50 g/L, and the appropriate ratio of arsenic to antimony and bismuth (29) is present, these elements do not codeposit on the cathode. 

When the copper content in the Dorn metal has been reduced to less than 1% by fire refining, the metal is cast into anodes for electrolytic separation of silver. A typical analysis of Dorn metal is... 

Table 5. U.S. Production of Copper-Bearing Ores and Recoverable Copper Content of Ores, t...

Purity. Electrolytic copper is one of the purest of the materials of commerce. The average copper content of ETP copper, for instance, is over 99.95%, and even the highest level of impurities other than oxygen are found only to the extent of 15—30 ppm. Up to 0.05% oxygen is present in the form of copper(I) oxide. Even at these low impurity levels, properties of interest to fabricators are affected in varying degree. 

Copper Hydroxide. Copper(II) hydroxide [20427-59-2] Cu(OH)2, produced by reaction of a copper salt solution and sodium hydroxide, is a blue, gelatinous, voluminous precipitate of limited stabiUty. The thermodynamically unstable copper hydroxide can be kiaetically stabilized by a suitable production method. Usually ammonia or phosphates ate iacorporated iato the hydroxide to produce a color-stable product. The ammonia processed copper hydroxide (16—19) is almost stoichiometric and copper content as high as 64% is not uncommon. The phosphate produced material (20,21) is lower ia copper (57—59%) and has a finer particle size and higher surface area than the ammonia processed hydroxide. Other methods of production generally rely on the formation of an iasoluble copper precursor prior to the formation of the hydroxide (22—26). 

The copper-rich amalgams have performed well in clinical trials in which they were compared with alloys having lower copper content. An improved marginal stability was observed, which may be associated with a longer clinical lifetime (136). These amalgams have also been called non-y2 amalgams, where refers to the compound Sn Hg comprised of Sn Hg [11092-12-9] and Sn Hg [11092-11-8]. 

One of the serious defects of the conventional amalgams is the corrosion of the Sn Hg phase, which is normally absent or, if it forms, mostiy disappears in amalgams with the increased copper content hence, the term non-y2 amalgams. The phases present in two conventional amalgams used in clinical testing (56,58,62) are... 

Replenishment should be done with caie. Massive additions can cause decomposition. Maximum stability of electroless baths is obtained when continuous replenishment is practiced. Colorimetric analy2ers are commonly used to control the addition of replenisher solutions in a set ratio based on the nickel or copper content of the bath. A number of machines are available that continuously analy2e plating baths and make additions based on each separately analy2ed component. 

Barrel plating of parts in copper cyanide solutions utilizes various formulations, some weaker, some stronger than the high speed baths. When plating parts that tend to stick together or nest during the barrel rotation, the free cyanide may need to be increased. This may require 35—40 g/L free potassium cyanide or more with an equal copper content. 

The electrolytes used were acetate buffer at pEI values 2, 4 and 6 and the same electrolyte is used in the presence of EDTA at pEI values of 2 and 6. Iron and copper contents could be most easily determined in EDTA medium at pH 6. The best medium for nickel was found to be as ammonia buffer pH 9.5 qg/L, it could be separated from zinc in this medium. The elements determined in white and red wine were Cu, Pb, Zn, Cd, Fe and Ni. The quantities found were for iron about 9000 qg/L, for copper 290 qg/L, Ni 80 qg/L, lead 150 qg/L and zinc 460 qg/L. The validation was made by determining each element under different conditions. 

In order to find optimal conditions for the soluble copper determination we examined the influence of electrolysis potential, electrolysis time, and the solution stirring rate on the accuracy and sensitivity of determination. We found that the optimal parameters for PSA determination of copper were electrolysis potential of -0.9 V vs. 3.5 mol/dm Ag/AgCl, electrolysis time of 300 s, and solution stirring rate of 4000 rpm. The soluble copper content in samples investigated in this study varied from 1.85 to 4.85 ppm. Very good correlation between the copper content determined by PSA and AAS indicated that PSA could be successfully applied for the soluble copper content determination in various dental materials. 

The corrosion rates of wrought iron and mild steel when immersed in seawater or buried in soil are not significantly different when the copper contents are similar. 

Where the retention of strength at elevated temperatures is required, then the alloys H12and H16 should be considered. Because of their copper content the corrosion resistance is mediocre and for service in aggressive environments the Al-lZn clad version to DTD 5070 would generally be preferred to the unclad metal. 

Common packaging materials are a potential source of aggressive substance s, and careful selection is recommended to avoid surface deterioration. Where paper is in contact with aluminium, the chloride content should be below 0-05 7o, sulphate content below 0-25 7o, copper content below 0-01% and the pH of aqueous extracts in the range pH 5-5-7-5, in order to avoid corrosion in damp conditions. Papers and felts used in building applications should also conform to this specification as a minimum requirement and be of the highest quality, since metallic copper found in materials of inferior origin can result in severe local galvanic attack of aluminium. 

In the tests described by Tracy, a high-tensile brass suffered severe dezinc-ification (Table 4.11). The loss in tensile strength for this material was 100% and for a non-arsenical 70/30 brass 54% no other material lost more than 23% during 20 years exposure. In Mattsson and Holm s tests the highest corrosion rates were shown by some of the brasses. Dezincification caused losses of tensile strength of up to 32% for a P brass and up to 12% for some of the a-P brasses no other materials lost more than 5% in 7 years. Dezinc-ification, but to a lesser degree, occurred also in the a brasses tested, even in a material with as high a copper content as 92%. Incorporation of arsenic in the a brasses consistently prevented dezincification only in marine atmospheres. 

In de-aerated conditions, for instance in most central heating systems, little if any attack on copper occurs . As far as drinking waters are concerned, copper is not classified as a toxic substance or hazardous to health. To avoid any difficulties due to unpalatability, the maximum continuous copper content should not exceed 10 p.p.m., with a limit of 3 p.p.m. in water after standing overnight in copper pipes. A review of the subject by Grunau makes reference to 394 published papers. 

Example 3. The mean (x) of four determinations of the copper content of a sample of an alloy was 8.27 per cent with a standard deviation s = 0.17 per cent. Calculate the 95 % confidence limit for the true value. 

---