The main use area of lead is battery manufacturing and lead isolation of underground communication cables lea is another important area of consumption. Corrosion-preventive lead has important usage areas in oxide paints, coating of cables, in the form of lead tetraethyl and tetramethyl as octane-regulating compounds, in the protection from x-rays since it is a least radiation-permeable metal, in the construction of coloured television tubes and in the manufacture of ammunition.

The lead with 34th place among the elements found on the earth has an atomic number of 82 and an atomic weight of 207.21. Lead, whose original crystal structure is rarely found in the nature, lead crystallizes in the cubic system. It is grey coloured and has metallic shine. Its melting point is low (327 °C) and boiling point (1 atmosphere) is 1525 °C. Lead, which is corrosion-resistant, easily shaped with high specific gravity (11,4 t / m3), can be used as different alloys. In cases, where tension is significant, its use is limited since it has a low tensile strength (1 t/in2). Besides being the most resistant to corrosion among ordinary metals, it is also a metal that has the flattening and wire drawing properties. Lead forms five types of oxidized compounds as PbO, Pb203, Pb04, Pb02 and Pb20. The most durable of all is PbO. The general characteristics of lead minerals observed in the nature are summarized as follows;

Galena (PbS):
It contains 86.6% of Pb and 13.4% of S. It may contain a small amount of iron, zinc, antimony, selenium, silver and gold. The silver content generally ranges from 0.01 to 2.0%. For this reason, it takes the name of lead glance. Its hardness is 2.3, specific gravity is between 7.4- and 7.6 and the colour is silver grey. The galena, which crystallizes in the cubic system, easily melts in the blow pipe flame.

Cerussite (PbCO3):
Cerussite is found on the galena fleets, sometimes in crystals and sometimes in dense and stalactite-shaped masses. The cerussite, which has single or grouped crystals, is in the rhombic crystal structure. It has a crispy structure with a hardness of 3-3.5 and specific gravity of 6.5. The pure colour of mineral, which may be yellow, grey brown and white in colour, is white.

Lead Products and Commercial Grading

Depending on the developing technologies and metal prices, mineral deposits containing 2% Pb + 5% Zn or 3% Pb + 2% Zn or a some Ag and Au, even it is in small amount, are economically operating. Due to the increased investment costs and low metal prices in recent years, the emphasis is on the operation of deposits containing silver and having a Pb + Zn grade greater than 10%. The grade for lead concentrates is 70-80% Pb. Bulk concentrates, which can be sold, may contain 30% Pb, 30-40% Zn, 4-5% Cu.

Depending on the imperial smelting processes applied to the concentrated products in transition to metal, the limits of base grade and other impurities are limited. Arsenic and antimony in lead concentrates and chlorine and fluorine in zinc concentrates are undesirable main impurities. Lead is a soft, heavy, malleable but non-wireable and highly resistant to corrosion. Commercial grading is given below.

Refined lead: It is the lead of which impurities have been removed with metallurgical methods. The grade of refined lead is at least 99.85% Pb. The refined lead is marketed in four different groups:

* Pure Lead: Refined lead in high purity grade.
* Chemical Lead: It is defined as lead which has a high purity but silver has not been removed from its content. This type of lead is usually derived from the lead ore extracted in Southern Missouri.
* Acid-Copper Lead: Lead obtained by adding copper to the refined lead.
* Normal Silver-free Lead: It is defined as refined lead of which silver has ben removed from its content.
The grading given above is based on the chemical requirements in ASTM B29-55 specifications, prepared for pig lead. Lead is also found on the market in the following forms:
Ingot lead Powder lead
Pig Lead Sheet Lead
Foil Wool lead
Shot (lead) Coating (lead)
Paints (lead) Extrusions
Cast lead
Lead is mostly alloyed with antimony, calcium and tin. These alloys are called "antimony" or "hard lead", "white metal", "meltable alloys" or "soft solder"

Usage Areas of Lead

The main use area of lead is battery manufacturing and lead isolation of underground communication cables lea is another important area of consumption. Corrosion-preventive lead has important usage areas in oxide paints, cable sheathing, in the form of lead tetraethyl and tetramethyl as octane-regulating compounds, in the protection from x-rays since it is a least radiation-permeable metal, in the construction of coloured television tubes and in the manufacture of ammunition.

Battery manufacturing:
Lead batteries are used not only in automobiles but also in many industrial and military systems where lighting, communication systems and electrical energy are to be stored. The plates of lead-acid batteries are sheets cast from the lead alloy. This alloy contains 6-12% antimony, and a small amount of arsenic, tin and other elements. It increases the resistance against corrosion by giving hardness to the antimony sheet. Tin enables the melt become a proper mould.

Tetraethyl lead (Pb(C2H5)4):
When hydrocarbon fuels are mixed with air, they ignite at appropriate heat and pressure without any electric spark. This event is the working principle of diesel engines. The desired combustion in the air-fuel mixture starts with the ignition of the mixture in the automobile cylinder. However, if the combustion of the fuel is not arranged according to the other factors connected to it, the emerging heat and pressure cause a severe explosion. This is called knocking, and the compounds used to reduce it are called antiknocks. Tetraethyl (tetramethyl) lead forms the active substance of this compound. Super petrol contains 2-4 ml of tetraethyl lead in one gallon (3.6 liters), while normal gasoline contains 0.5-1.5 ml of tetraethyl lead.

Litharge (Lead oxide):
Besides the manufacturing of positive and negative plates of batteries, they also fined fields of use in ceramics, lead chromate, varnish, insecticide, tire making and oil refinery. Also, it is the main chemical used for melting gold in the "Fire Assay" method.

Cable sheathing:
It is used as lead sheathing in telephone and telegraphic communications, in electrical transmission and distribution cables. The main function of the lead sheath is its resistance to moisture and other destructive factors. With this feature, it is used in the construction of underground cables. In some cases, antimony (1%), calcium (0.04%) and arsenic (0.1-0.2%) are added to make it harder.

Caulking Lead:
With its resistance to corrosive agents, flexibility and low melting point, lead is used in joints of water pipes. Caulking lead contains 99.73% pure lead and less than 0.08% of arsenic, antimony, tin, copper, zinc, iron and silver. Bismuth content should be maximum 0.25%. As a general condition, about 1 pound (0.454 kg) lead is required for each inch of pipe diameter in pipe caulking.

Lead wool:
Lead yarn is obtained by sieving melted lead. This yarn is used to prevent leaks in the taps of oil wells.

In general, the solder contains 30-40% Pb and 60-70% Sn. In solders desired at plastic level, tin is below 40% and lead is above 60%. The melting point is 183 °C

Journal bearing alloys:
These materials, which are used as a moving partition support and link between the moving and fixed parts of the machine, are lead, tin and copper based alloys.

Ablative alloys:
They are used in anchor melds, magnets, staples, compressing gas cylinders, manufacturing of plugs and fire-resistant door construction and similar areas.

Lead leaf:
It has a thickness of 0.01 mm. It is used in some types of electrical condenser. Due to its resistance to moisture and radiation, it is used in packaging and photo-film in medical industry, in dentistry and radiography industry. In addition, in the military field it is used to protect ordnance material from light and moisture, and to pack good quality teas.

With its high specific gravity, ease of casting and low cost its use as ballast material is widespread. One ton of lead is used for each pair of wheels of a steam locomotive. It is used in machine balances, car wheel balances, anti-aircrafts, keels and airplane propellers.

Radiation shield:
Lead has the ability to reduce dangerous radiation, especially gamma radiation. Gamma and neutron rays distort the living tissues because of their ionizing properties. Lead absorbs these rays. It can be used continuously without being contaminated or become radioactive. Lead used in the sheathing must contain substances that may become radioactive as a result of high energy radiation. Cadmium or paraffin and hydrogenated substances such as water are used as protective against neutrons. However, because of the fact that when the neutrons are absorbed, they ray out gamma rays, they need to be stopped with lead shields.

Vibration absorber:
In the structures close to vibration sources such as railways, lead and asbestos blocks are placed under column bases. Various sensitive instruments are mounted on lead blocks or covered with lead sheaths to protect them from vibrations. When the piping system is installed in the ships, the pipes are insulated with lead straps in order to prevent vibration.

Glass, glaze and polish:
Red lead, white lead, litharge and lead silicates are used in glass, glaze and polish. Leaded-glass has a high refractive index, thermal conductivity and chemical stability are less than lead-free glass. It provides shine and resonance to the glass. A good quality crystal may contain 30% litharge. The lead used in glass and polish should be of high purity in order to prevent discolouration.

Malleable brass
: Brass contains around 61.5% Cu and 3% Pb and 35.5% Zn. In order to increase the malleability of brass, lead is usually added in an amount of 0.25-6%. Cutting tools are made of leaded materials. Lead is added to increase the malleability properties of aluminium and steel. Leaded tin bronze (88% Cu, 6% Sn, 1.5% Pb and 4.5% Zn) is used in manufacturing of valves, support pieces and bends while leaded nickel brass (57% Cu, 2% Sn, 9% Pb, 20% Zn, 12% Ni- German silver) is used in the casting alloy. Lead bronze is used in journal bearings and the Pb content is over 30%. Leaded red and yellow brass are used in pipe sets, metalware and carburettors.

Semiconductor lead:
Thermoelectric lead telluride is used to generate electricity directly from the nuclear reaction heat. In the US, lead sulphide was used to collect information about the water content in the atmosphere during the Nike-Cojun rockets flight. The electrical output of lead sulphide varies according to the water vapour of the atmospheres.

Lead Paints:

- White lead (Cerusa): The approximate formula is 2PbCO3.Pb(OH)2. Basic lead carbonate or white lead is a white paint that has been used for many years. It is also used in making pottery glaze, polish and glazier’s putty.
- Red lead (Vermillion): It has a significant place in the paint industry. It is a standard type of paint used for preventing corrosion and rust in iron bridges, steel structures, ship boats and water and fuel tanks. It increases flexibility by increasing resistance of paint film.
- Orange mineral: It is a bright red rock which is used for colouring and making printing ink. Its chemical composition and construction is similar to the red lead.
- Lead chromate (PbCrO4): It is a bright yellow rock which is precipitated by the addition of potassium or sodium bichromate to the lead acetate (or nitrate) solution. If the solution is buffered with sodium hydroxide before adding bichromate, a yellow-orange precipitate forms.
- Basic lead chromate: It is named as American red, Chinese red or chrome red, and is made from white lead. It is a mixture of chromium green, yellow lead chromate and Prussian or Chinese blue.
- Basic lead silicate: The paint, which forms a complex saline of lead oxide and silica, is made with litharge, silica and sulfuric acid.
- Basic lead sulphate: It is a white, opaque paint with the same properties as the basic lead sulphate. It is obtained by combustion of galena concentrates or by reaction of the lead with sulphur dioxide in hot air. Some plastics are used as stabilizers.
- Blue lead: It has basic lead sulphate and a small amount of lead sulphide, zinc oxide and carbon with bluish grey colour. It is used as anti-rust.

Lead Substitutes

In some areas, there are various materials used in substitution for lead. For example in batteries nickel-cadmium, mercury, nickel-zinc, silver-zinc, iron and carbon-zinc compounds can be used instead of lead. However, their electrical properties are different and the sources of raw materials, which they are derived from, are not sufficient. In addition, most of them are more expensive than lead. Only in special applications, where high energies are required, other expensive materials may be preferred instead of large-volume lead-acid batteries. Lithium sulphide, sodium sulphide and zinc chloride amulets among batteries being developed for possible use in electric vehicles have theoretically more energy capacity than lead-acid batteries. However, lithium sulphur and sodium sulphur are more efficient at higher temperatures (over 300 °C) while zinc chloride types are more efficient at lower temperatures (0-10 °C). A manganese compound called MMT is used as a gasoline additive. Some other metal compounds may also be used instead of lead as additives. However, these are less convenient and much more expensive than lead and they cause environmental problems. Octane level can be increased in refineries, but if lead is not added, efficiency of gasoline decreases. Car designs have been made to use unleaded gasoline, the unleaded gasoline trade has been increasing steadily and the average lead ratios in all fuels have been reduced since 1974.

Lead is no more used in the interior paints, due to its toxic effects. Titanium and zinc are preferred for exterior paints. Due to its resistance to rust and corrosion, lead paint maintains its characteristic of being the basic material in constructions and highways. In places, where high corrosion does not cause a problem, polyethylene and metallic or organic compounds are used in underground and communication cables in substitution for lead. Lead competes with plastics, galvanized steel, copper and aluminium in construction. Plastic and asbestos cemented pipes are also substitute lead pipes. In corrosive chemical environments, stainless steel, titanium, plastics and cement are used instead of lead, and plastics are used in caulking and joints. Iron and steel substitute lead in the ammunition. In tubes and similar cups, plastics, aluminium, tin and glass are preferred.

Resource: MTA

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