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Magnesium is a chemically active, moderately hard, silvery metal. It is the lightest structural metal, being one-third lighter than aluminum.

Properties

Magnesium oxidizes and tarnishes in moist air but not in dry air and is attacked by salt water. Magnesium is soluble in moist acids, insoluble in water, nontoxic, and nonmagnetic. In finely divided form it will ignite easily, but solid magnesium will not burn unless heated above its melting point.

Workability

Magnesium can be worked by all the usual methods. It can be cast, extruded, rolled, drawn, spun, forged, blanked, and coined. It can be brazed with special care. It can be riveted and welded by gas, arc and resistance welding.

Structural Uses

The major structural use of metallic magnesium at present is in alloy form for the aircraft, automotive, machine tool, and railroad industries, where its weight is important. When small quantities of aluminum, manganese, zirconium, zinc, rare earth metals, and thorium are combined with magnesium, the resulting alloys have excellent physical properties.

Uses of magnesium alloys in construction field have been confined to household equipment and small accessories. But, since magnesium is so abundant and has so many characteristics valuable in a structural metal, it is possible to forecast a large development of its uses in construction in the future.

Magnesium is also used for expendable anodes with other metals, which then serve as cathodes, to protect them from corrosion. For example, underground pipelines, well casings, and tanks are protected by placing magnesium anodes, connected by wires, adjacent to them. Any corroding action takes place with the magnesium and not with the other metal.

Ø Application as a metal

Magnesium is the third most commonly used structural metal, following steel and aluminum. Magnesium compounds, primarily magnesium oxide, are used mainly as refractory material in furnace linings for producing iron, steel, nonferrous metals, glass and cement. Magnesium oxide and other compounds also are used in agricultural, chemical and construction industries. As a metal, this element's principal use is as an alloying additive to aluminum with these aluminum-magnesium alloys being used mainly for beverage cans.

Magnesium Alloys

Magnesium alloys are utilized in engineering design mainly because of their high strength-weight ratios, excellent machinability, and relatively low cost on a piece basis. Alloys of magnesium are found to be especially useful in transportation and portable equipment as well as for parts, which are subject to frequent and rapid changes in position.

Ø Properties of Magnesium Alloys

· Light weight

· Low density (two thirds that of aluminium)

· Good high temperature mechanical properties

· Good to excellent corrosion resistance

Nickel

NICKEL

Nickel is a silver-colored metal mainly used as an alloying element. It provides increased resistance to atmosphere and chemical corrosion and increases the strength of the alloy.

Properties

Nickel is resistant to strong alkalis and many acids. It has good resistance to corrosion and oxidation and is strong and tough.

Working Characteristics

Nickel can be fabricated using most of the commonly used processes, such as hot- and cold-rolling, extruding, bending, forging and spinning. It can be joined by some welding process, soldered, brazed, or joined with mechanical fasteners.

Production of Nickel

Several processes are used to produce nickel from the ore. The most recent is the Hybinette process developed in Canada. The ore is processed using the Bessemer process from which the molten goes to a cooling chamber. From here it is crushed and ground and magnetically separated. The result is a nickel-copper platinum alloy that is treated by the electrolysis process to separate the nickel, copper, and platinum.

Uses of Nickel

In addition to its use as an alloying element in ferrous and nonferrous metals, nickel is also an excellent material to use for electroplating and electroless plating. Electroplating is the process of depositing a coating of metal on another metal by electrolysis. Electrolysis is a method of plating a material by chemical means in which the piece to be plated is immersed in a reducing agent that, when catalyzed by certain materials, changes metal ions to metal, forming a deposit on the surface of the piece. Nickel is used in electric heating elements, lamp filaments, and plumbing fittings.

The nickel alloys of particular interest to the construction field are certain steels (low-nickel), stainless steels, Monel metals, aluminum, steel, and iron alloys, and nickel silvers. Each of these is important enough to merit discussion under a separate heading. Other alloys having important specialized applications but less used in construction field are heat-resistant alloys and electrical resistance alloys; thermal expansion alloys; and high nickel-copper, copper-nickel and coinage alloys. There are also special nickel alloys and super alloys for industrial, transportation, and chemical field.

Nickel Alloys

A major use for nickel is as an alloying element. The alloying of nickel to other metals provides increased ductility, corrosion resistance, strength, hardness, and toughness. Nickel alloyed to nonferrous metals improves electrical resistance and magnetism and helps control expansion.

Inconel 600 is a special nickel alloy containing about 75 percent nickel, 15 percent chromium, and 7 percent iron. Other nickel alloys include those used for electrical resistance coils, magnetic and nonmagnetic alloys containing iron, alloys designed to have a high coefficient of thermal expansion that are used in the production of glass, and copper-nickel alloys used for products exposed to marine conditions.

Monel is an alloy of approximately two-thirds nickel and one-third copper that has many uses in construction and industry.

Zinc

ZINC

Zinc (chemical symbol Zn) is a bluish white metal that is brittle and has low strength. It is often referred to as a white metal and is widely used as a protective coating over steel.

Properties

Zinc has low strength and is brittle. Although it can be damaged by alkalis and acids, it resists corrosion by water and forms a protective oxide when exposed to air. It is also subject to creep. The tensile strength can be greatly increased by cold-working and alloying.

Working Characteristics

Since zinc is a soft material, it can be hot- and cold- rolled, drawn, extruded, cast and machined. It can be joined by welding, soldering and various mechanical fasteners.

Production of Zinc

Zinc is extracted from zinc blende (sphalerite) ore. The mined ore is crushed and ground and the ore particles are separated from the rock. Element such as copper, lead and iron sulfides tend to be in the ore and are separated by a flotation process. This involves separating the element in the finely grained ore by floating them on a liquid. The floating capacity of the various elements varies. The lead and copper sulfates will float off the top of the liquid. Chemicals are added to cause the zinc sulfide to float and be taken off. This concentrated zinc material is dried and ready to be refined into the metal zinc.

The electrolytis process involves roasting the zinc concentrate and removing soluable parts whit a weak sulfuric acid solution. The solution is filtered to remove some of the other metals. Finally, this solution is moved to electrolytic tanks where cathodes of pure aluminum and anodes of lead or lead-silver are lowered into the tank and electric current is passed between them through the solution. Pure zinc is attracted to and plates the cathodes. The layer is removed, melted and poured in slabs for processing into various applications.

The vertical furnace method involves mixing coking coal briquettes and the dried zinc concentrate into the top of a vertical furnace where they are heated until the zinc concentrate vaporizes. The vapor is removed and into a solid. The solid zinc slabs are ready for use in producing various products.

Uses of Zinc

The major use for zinc is to form a protective coating over steel. This is referred to as galvanizing. Galvanizing involves placing the steel to be coated into a bath of molten zinc, which bonds to the surface. It is important that the coating be free of imperfections such as pinholes that would permit moisture to reach the steel and cause it to rust. Both galvanized sheet and strip material are available.

Since zinc and zinc alloys have low melting temperatures, they are easy to cast and used for some types of hardware and plumbing items. They are usually die cast and finished by polishing or plating with chromium, brass or other materials.

Zinc also finds use as an alloying element in brasses. Various zinc compounds find use in the production of paper, plastics, ceramics, rubber, abrasives, paint and other products. Zinc is also used for specialized products in which corrosion resistance is important, such as anchors, flashing, screws, nails, expansion joints, and corner beads. Solid zinc strip material used to produce a wide range of products, such as low-voltage buss bars, cavity wall ties, electric cable binders, electric motor covers, grading screens, and roofing and fascia material.

Zinc is high on the galvanic table of electrolytic potentials. This means it can be used to coat a material lower on the table to protect the material if galvanic action does occur. The zinc will be sacrificed, thus protecting the coated metal.

Zinc Alloys

Zinc alloys used for die casting consist of about 95 percent zinc and 4 percent aluminum and magnesium. Some copper may be present.

Tin

TIN

Tin (chemical symbol Sn) is produced from the ore containing the mineral cassiterite, which is a tin oxide. Since there is little cassiterite in North America, tin has to be imported from Malaysia, Brazil, Russia, Indonesia, Thailand, China and Bolivia. The ore usually contains little tin, so an extensive refining process is required.

Properties of Tin

Tin is soft metal that is malleable and ductile and blue-white in color. It is corrosion resistant when exposed to air and moisture. It will take a high polish and has properties enabling it to coat other metals.

Work Characteristics

Because tin is soft and malleable, it can be worked by rolling, spinning, extrusion and casting.

Production of Tin

After the ore is mined the impurities must be removed to get a concentrated ore. This involves a series of mechanical and chemical processes for crushing and cleaning the ore. Magnetic separators and screening operations are used from which the ore and the tailings are separated.

The concentrated cassiterite is refined, producing a high-purity metal of at least 99.8 percent tin. Several different processes are used but they all involve smelting (melting) the ore in a furnace in which a crude tin is separated from the slag. The crude tin is then heated to a predetermined temperature at which impurities with higher melting temperatures than tin remain. This process is called liquidation. This partly pure tin is drawn off and heated above its boiling point. As it is stirred, additional impurities rise to the surface and are drawn off. This continues until impurities are removed, leaving an almost pure tin.

Uses of Tin

Since tin and tin alloys have high corrosion resistance and excellent coating ability, they are used extensively to provide protective coatings on other metals, especially steel. One example is a coating on cans used to store food for retail sale. Tin is also used as an alloying element in other metals. Its low melting point makes it useful in some solders. It finds applications in mirrors, hardware and fusible alloys. Tin compounds are used in the production of glazed, glass and porcelain enamel

Aluminium

Aluminium is a relatively new material, compared with iron, but it is finding increased use in the building industry. The process now used for extracting aluminium from its ore, bauxite, requires tremendous amounts of electricity which about 10kWh for each pound of metal. As a consequence, any large aluminium-extraction industry must be located near the source of abundant low cost electric power at present hydroelectric power.

The ore is strip-mined in various parts of the world and shipped to smelters located near large hydroelectric power developments. Other essentials ingredients in the manufacture of aluminium are petroleum coke, cryolite and fluorspar.

Properties of aluminium

Aluminium is highly resistant to weather and to corrosive industrial and seacoast atmospheres. Although exposure causes surface oxidation and dulling, the metal is not weakened structurally. The oxide form an added protective coating, so that the weathering rate soon tends to level off. The average penetration of weathering on architectural alloys is not much deeper after half a century than after 2 years. Exposure in a typical industrial atmosphere produces pitting to an average depth of only 0.003 in [ 0.08 mm] after 52 years.

Pure aluminum (99.996 % pure) is the most corrosion-resistant form of aluminum or its alloys, but it is extremely soft and weak. Alloys of aluminum with chromium, manganese and silicon are still highly resistant to corrosion, alloy containing appreciable amounts of copper are more susceptible to corrosion. The addition of Zinc improves the machining qualities of aluminum. Nickel increases it hardness.

Production of aluminum

Aluminium is a strongly reactive metal that forms a high-energy chemical bond with oxygen. Compared to most other metals, it is difficult to extract from ore, such as bauxite, due to the energy required to reduce aluminium oxide (Al₂O₃). For example, direct reduction with carbon, as is used to produce iron, is not chemically possible, since aluminium is a stronger reducing agent than carbon. Aluminium oxide has a melting point of about 2,000 °C. Therefore, it must be extracted by electrolysis. In this process, the aluminium oxide is dissolved in molten cryolite and then reduced to the pure metal. The operational temperature of the reduction cells is around 950 to 980 °C. Cryolite is found as a mineral in Greenland, but in industrial use it has been replaced by a synthetic substance. Cryolite is a chemical compound of aluminium, sodium, and calcium fluorides: (Na₃AlF₆). The aluminium oxide (a white powder) is obtained by refining bauxite in the Bayer process of Karl Bayer. (Previously, the Deville process was the predominant refining technology.)

The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with potassium. Both of the electrodes used in the electrolysis of aluminium oxide are carbon. Once the ore is in the molten state, its ions are free to move around. The reaction at the cathode (negative electrode) is

Al³⁺ + 3 e⁻ → Al

Here the aluminium ion is being reduced (electrons are added). The aluminium metal then sinks to the bottom and is tapped off.

At the anode (positive electrode), oxygen is formed:

2 O²⁻ → O₂ + 4 e⁻

This carbon anode is then oxidized by the oxygen, releasing carbon dioxide.

O₂ + C → CO₂

The anodes in a reduction cell must therefore be replaced regularly, since they are consumed in the process.

Unlike the anodes, the cathodes are not oxidized because there is no oxygen present, as the carbon cathodes are protected by the liquid aluminium inside the cells. Nevertheless, cathodes do erode, mainly due to electrochemical processes. After five to ten years, depending on the current used in the electrolysis, a cell has to be rebuilt because of cathode wear.

Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologically. The worldwide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters achieve approximately 12.8 kW·h/kg (46.1 MJ/kg). (Compare this to the heat of reaction, 31 MJ/kg, and the Gibbs free energy of reaction, 29 MJ/kg.) Reduction line currents for older technologies are typically 100 to 200 kA; state-of-the-art smelters,operate at about 350 kA. Trials have been reported with 500 kA cells.

Used of aluminum

• Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles etc.)
• Packaging (cans, foil, etc.)
• Water treatment
• Treatment against fish parasites such as Gyrodactylus salaris.
• Construction (windows, doors, siding, building wire, etc.)
• Cooking utensils
• Electrical transmission lines for power distribution
• MKM steel and Alnico magnets
• Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.
• Heat sinks for electronic appliances such as transistors and CPUs.
• Substrate material of metal-core copper clad laminates used in high brightness LED lighting.
• Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.

Lead

Lead

Lead is a blue-gray, soft very heavy metal which is the heaviest of the common metals. It is extremely workable, has good corrosion resistance, is easily recovered from scrap materials and is relatively impenetrable to radiation.

It has a characteristic of corrosion resistance, this corrosion resistance arises from the fact that metallic lead does not react with many compounds or solutions, and with certain others it forms compounds that act as protective coatings against further action or corrosion.

Lead in fume, vapor or dust form and lead compounds are toxic if ingested in measurable quantity. Lead carbonate and lead sulfate have been almost complicatedly eliminated as the white paint solid in interior paints because of the lead poisoning of children from lead base paint. The only exception is basic lead silicochromate, which is nontoxic.

When the commercial, the lead is represent extruded as form of pipe, rod, wire, ribbon, cames, traps, bends, wedge lead, and special shapes. Lead also rolled into sheet, foil, strip, blanks for drawing, and blanks for various shapes. It also cast as sand or die castings; and in miscellaneous forms including metallic powder, wool and shot.

Types and uses

There are several grades of lead metal, of which corroding lead, chemical lead and common desilverized lead are of interest to the construction field. Corroding lead is used for fine white lead paints, red lead, litharge, and orange mineral. Chemical lead and common desilverized lead are used for sheet, pipe, lead wool, powered lead, ribbon lead and alloys.

Lead fines many uses in rough hardware items such as expansion shields for securing bolts, screws and other accessories in masonry, washers, lead headed nails and so on.

There also some specialized uses of lead in construction, for example, as an anti spar material for floors in areas where explosions may occur, in chemical laboratories for sinks, pipes and special equipment, and as a shield against radiation.

Another interest used for lead is in the form of lead azide. Lead azide is easily exploded by an electrically heated wire, so it is used in the manufacturing of blasting caps, which to set off other explosives.

Brass

Brass

A yellowish alloy of copper and zinc, sometimes including small amounts of other metals, but usually 67 percent copper and 33 percent zinc. (American Heritage Dictionary). The other materials added to the brass to give special qualities. The copper-zinc proportion may vary from 95% copper and 5% zinc to 55% copper and 45% zinc. Brass varies in color from lemon yellow to deep golden brown according to the amount of zinc: 10%zinc for bronze color; 15% zinc for golden; 20-38% zinc for yellow; and above 45% zinc for silvery white.

Brass is stronger and harder than copper, but not as strong or hard as steel. It is easy to form into various shapes, a good conductor of heat, and generally resistant to corrosion from salt water. Because of these properties, brass is used to make pipes and tubes, weather-stripping and other architectural trim pieces, screws, radiators, musical instruments, and cartridge casings for firearms.

Classification

Alpha brasses are ductile and can be both cold-worked without annealing and hot-worked. Corrosion resistence and electrical and thermal conductivity are fair, these properties decreasing with a decrease in copper content. Alpha brasses have a wide range of color. Copper-base alloys containing more than 64% copper are known as alpha brasses.

Alpha-Beta brasses are copper-base alloys containing from 64% down to 55% copper, and containing between 36% and 45% zinc. They have comparatively high tensile strength and hardness, fairly low melting points, and relative poor corrosion resistance and electrical conductivity. They can be easily hot worked and within limits can be cold work without annealing. Their color range is important because as the copper content decreases, they become less red and at 55% copper the color practically matches that of commercial bronze ; therefore complicated shapes may be made by hot extrusion and used with sheets of commercial bronze.

Leaded brasses are those to which lead is added to increase machinability. They maybe either Alpha or Alpha-Beta brasses and are especially suited for free-machining purposes. They can be easily hot-worked (however, the metal must be supported mechanically) and cold-worked within limits, but they are not as strong, corrosion resistant, or hard as the Alpha and Beta brasses.

Tin brasses also called naval brasses, are used for chemical, steam power plant, and marine equipment.

Manganese-tin alloy is used as substitute for nickel silver, and manganese brass (bronze) is used where high strength and resistance to seawater are required.

Type and use

In the construction field, brasses are used for doors, windows, door and window frames, and ornamental metalwork such as railings, trim and grilles. The brasses are used for finish hardware, plating of hardware, and other miscellaneous accessories such as screws, nut and bolts, anchors, weatherstripping, and ties.

The bulk of brass produced is use in plumbing, heating, and air conditioning and in industrial machinery and equipment, where the special properties of brasses are required.

Introduction

Aluminum metal does not occur in nature.It is made by the electrolysis of a molten mixture of bauxite (aluminum oxide ore) and cryolite (sodium aluminum fluoride). In additional to its light weight, ithas moderate resistance to corrosion due to the rapid formation of a thin, transparent, tightly adherent aluminum oxide coating. Thicker oxide coating are produced by an electrotic process known as anodizing. Non ferrous metal consist of aluminum,brass,lead, tin, zinc, nickel and magnesium.