Copper—zinc—aluminum systems

Other Systems. Evidence for dealloying has been reported in austenitic stainless steel and iron-nickel alloys in acidified chloride-containing solutions, reduction of titanium dioxide in molten calcium chloride, and copper-zinc-aluminum alloy pellets in NaOH solutions to produce Raney metal particles. (Corcoran)5... 

For ethylene glycol systems copper tubing is often used (up to 3 in), while pumps, cooler tubes, or coils are made of iron, steel, brass, copper, or aluminum. Galvanized tubes should not be used in ethylene glycol systems because of reac tion of the inhibitor with the zinc. Methanol water solutions are compatible with most materials but in sufficient concentration will badly corrode aluminum. 

The vendor claims that the following metals have been successfully treated to parts per biUion (ppb) and detection limit levels aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, molybdenum, nickel, selenium, silver, tin, uranium, vanadium, and zinc. The system is also able to remove ammonia, nitrates, phosphates, potassium, fluorides, and sodium. Studies have also been performed using Aqua-Fix to remove radionuchdes such as uranium from waste streams. 

Binary and ternary systems containing copper, zinc oxide and aluminum are widely used for industrial methanol synthesis. The adsorption of CO on a fully reduced and clean Cu surface is fully reversible at room temperature, with heats of adsorption ranging between 70 kj mol at low coverage and 45 kj mol" at high coverage [88]. 

Sanders et al. (1983) have also shown that the effects of Cu(II) on the growth of crab larvae and on their metallothionein with copper chelate buffer systems must be interpreted on the basis of free Cu ion activity. The data obtained reveal predictable relations between [Cu ] in seawater and processes at the cellular and organismic levels. Similarly, the uptake of metal ions by plants (e.g., of aluminum) is usually related to free metal-ion activity. Others have shown that the chelation of a variety of metals reduces the toxicity of metals to organisms for example, a reduction in the uptake of mercury by fish in the presence of EDTA and cysteine a reduction in copper and/or zinc toxicity to... 

When higher-temperature heat is available, other systems are possible. A school in Munich, Germany, dehydrated 7 metric tons of zeolites using 130°C steam in the district heating system during off-peak hours, then passed moist air over them in the day to recover the heat.201 Pellets of calcium hydroxide containing zinc, aluminum, and copper additives were dehydrated to calcium oxide using solar heat from a solar concentrator then the reaction was reversed to recover the heat.202 Zeolite 13X has been used to store carbon dioxide obtained from the decomposition of calcium carbonate at 825°C (15.2).203 Such temperatures are available with solar furnaces (where a whole field of mirrors focus on the reaction vessel). 

ISO CORRAG [23], the International Organization for Standardization (ISO) has implemented a classification system for evaluating atmospheric corrosivity and on the basis of variables that are fairly easy to obtain [24, 25]. This ISO classification has found several applications, for example, to predict the long-term corrosion behavior in different environments and to evaluate the effect of protective coatings. It contains two principally different approaches of assessing the corrosivity of any outdoor atmospheric environment. The first is based on exposure of standard specimens of steel, copper, zinc, and aluminum for one year whereby the corrosion effect is measured through mass loss measurements. One of five measured corrosivity classes... 

Among the non-ferrous metals, zinc, aluminum, and copper are most often employed in outdoor applications such as buildings, installations and transportation systems. Table 8.24 indicates the average corrosion rates of these metals in different types of atmosphere. Compared to steel, these rates are rather small. The values given in parentheses indicate the maximum depth of pits (in jtm) after twenty years of exposure time. 

Moist ammonia corrodes copper, zinc, and their alloys. It is customary, therefore, that iron or steel is used in piping and fittings. Certain aluminum alloys are used in appurtenances and can be used in other parts of systems for ammonia. 

Nonferrous metallurgy is as varied as the ores and finished products. Almost every thermal, chemical, and physical process known to engineers is in use. The general classification scheme that follows gives an understanding of the emissions and control systems aluminum (primary and secondary), beryllium, copper (primary and secondary), lead (primary and secondary), mercury, zinc, alloys of nonferrous metals (primary and secondary), and other nonferrous metals. 

As shown in Table 11.1, hydrothermal emissions are a major source of soluble iron, manganese, and zinc and a minor source of aluminum, cobalt, copper, and lead. Other elements with significant hydrothermal inputs include lithium, rubidium, cesium, and potassium. Considerable uncertainty also surroimds these flux estimates because they are the result of extrapolations from measurements made at a small number of hydrothermal systems at single points in time. These fluxes appear to vary significantly over short time scales as tectonic activity abruptly opens and closes cracks in the oceanic crust. 

It was pointed out by Hume-Rothcry 4 in 1926 that certain interns etallic compounds with close]y related structures but apparently unrelated stoichiometric composition can be considered to have the same ratio of number of valence electron to number of. atoms,. For example, the j8 phases of the systems Cu—Zti, Cu—-Alv and Ou -Sn are analogous in structure, all being based on the -4.5 arrangement their compositions correspond closely to the formulas CuZn, CusAl, and CtttSn. Considering copper to be univalent, zinc bivalent, aluminum trivalent, and tin quadrivalent, we see that the ratio of valence electrons to atoms has the value f for each of these compounds ... 

---