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Uses for Lead Compounds

Lead and Lead Alloys

Products and Applications

Federal Register, November 2, 1994: Lead is a soft, bluish metallic element mined from rock and found in its natural state all over the world. Lead is virtually indestructible, is non-biodegradable, and has been known since antiquity for its adaptability in making various useful items. In modern times it has been used to manufacture many different products, including paint, batteries, pipes, solder, pottery, and gasoline.

From the turn of the century through the 1940's, paint manufacturers frequently used lead as a primary ingredient in many oil-based interior and exterior house paints. Usage gradually decreased throughout the 1950’s and 60’s as latex paints (which are generally lead-free) became more widespread. The Consumer Product Safety Commission (CPSC) banned lead-based paints from residential use in 1978.  Currently, paint may not have more than 0.06% lead by weight.

HUD estimates that 75 % of the houses built in the United States before 1978 contain some lead-based paint. By current estimations, approximately 57 million homes may contain lead-based paint. Thus, lead-based paint may pose a potential hazard to the occupants under some conditions.

Lead affects virtually every system of the body. While it is harmful to individuals of all ages, lead exposure is especially harmful to children, fetuses, and women of childbearing age. Results of recent studies suggest that lead’s adverse effects occur at blood-lead levels previously thought to be safe; in fact, there does not yet appear to be a discernible threshold for the adverse effects of lead on the young.

In 1991, the Secretary of the Department of Health and Human Services characterized lead poisoning as the "number one environmental threat to the health of children in the United States."

Although the percentage of children with elevated blood-lead levels has declined over the last 20 years with the reduction of lead in gasoline, millions of U.S. children still have levels of lead in their blood high enough to seriously threaten their health.

Lead-based paint poses a health threat through various routes of exposure. Children under age 6 may ingest lead-based paint chips from flaking walls, window, and doors. Lead from exterior house paint can flake off or leach into the soil around the outside of a home, contaminating children’s playing areas. Dust caused during normal lead-based paint wear (especially around windows and doors) can create an invisible film over surfaces in a house. In some cases, cleaning and renovation activities can actually increase the threat of lead-based paint exposure by dispersing fine lead dust particles in the air and over accessible household surfaces. Both adults and children can receive hazardous exposures by inhaling the fine dust or by ingesting paint-dust during hand-to-mount activities.

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Uses for Lead Compounds:

Lead monoxide (PbO) also known as "litharge," is a yellow solid that is used to make some types of glass, such as lead crystal and flint glass, in the vulcanizing of rubber and as a paint pigment;

Lead dioxide (PbO2) is a brown material that is used in lead-acid storage batteries;

Trilead tetraoxide (Pb3O4) also known as "red lead," is used to make a reddish-brown paint that prevents rust on outdoor steel structures;

Lead arsenate [Pb3(AsO4)2] has been used as an insecticide although other, less harmful, substances have now largely replaced it;

Lead carbonate (PbCo3), also known as "cerussite," is a white, poisonous substance that was once widely used as a pigment for white paint. Use of lead carbonate in paints has largely been stopped in favor of titanium oxide (TiO2);

Lead chromate (PbCro4), also known as "crocoite," is used to produce chrome yellow paint;

Lead nitrate [Pb(No3)2] is used to make fireworks and other pyrotechnics;

Lead silicate (PbSiO3) is used to make some types of glass and in the production of rubber and paints.

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Lead and Lead Alloys

Compositions and Grades

Listed below are the Unified Numbering System (UNS) designations for various pure lead grades and lead-base alloys.

• Pure leads L50000 - L50099
• Lead - silver alloys L50100 - L50199
• Lead - arsenic alloys L50300 - L50399
• Lead - barium alloys L50500 - L50599
• Lead - calcium alloys L50700 - L50899
• Lead - cadmium alloys L50900 - L50999
• Lead - copper alloys L51100 - L51199
• Lead - indium alloys L51500 - L51599
• Lead - lithium alloys L51700 - L51799
• Lead - antimony alloys L52500 - L53799
• Lead - tin alloys L54000 - L55099
• Lead - strontium alloys L55200 - L55299

Grades of lead

Grades are pure lead (also called corroding lead) and common lead (both containing 99.94% min lead), and chemical lead and acid-copper lead (both containing 99.90% min lead). Lead of higher specified purity (99.99%) is also available in commercial quantities. Specifications other than ASTM B 29 for grades of pig lead include federal specification QQ-L-171, German standard DIN 1719, British specification BS 334, Canadian Standard CSA-HP2, and Australian Standard 1812.

Corroding Lead. Most lead produced in the United States is pure (or corroding) lead (99.94% min Pb). Corroding lead which exhibits the outstanding corrosion resistance typical of lead and its alloys. Corroding lead is used in making pigments, lead oxides, and a wide variety of other lead chemicals.

Chemical Lead. Refined lead with a residual copper content of 0.04 to 0.08% and a residual silver content of 0.002 to 0.02% is particularly desirable in the chemical industries and thus is called chemical lead.

Copper-bearing lead provides corrosion protection comparable to that of chemical lead in most applications that require high corrosion resistance. Common lead, which contains higher amounts of silver and bismuth than does corroding lead, is used for battery oxide and general alloying.

Lead-Base Alloys

Because lead is very soft and ductile, it is normally used Commercially as lead alloys. Antimony, tin, arsenic, and calcium are the most common alloying elements. Antimony generally is used to give greater hardness and strength, as in storage battery grids, sheet, pipe, and castings. Antimony contents of lead-antimony alloys can range from 0.5 to 25%, but they are usually 2 to 5%.

Lead-calcium alloys have replaced lead-antimony alloys in a number of applications, in particular, storage battery grids and casting applications. These alloys contain 0.03 to 0.15% Ca. More recently, aluminum has been added to calcium-lead and calcium-tin-lead alloys as a stabilizer for calcium. Adding tin to lead or lead alloys increases hardness and strength, but lead-tin alloys are more commonly used for their good melting, casting, and wetting properties, as in type metals and solders. Tin gives the alloy the ability to wet and bond with metals such as steel and copper; unalloyed lead has poor wetting characteristics. Tin combined with lead and bismuth or cadmium forms the principal ingredient of many low-melting alloys.

Arsenical lead (UNS L50310) is used for cable sheathing. Arsenic is often used to harden lead-antimony alloys and is essential to the production of round dropped shot.

Properties of Lead

The properties of lead that make it useful in a wide variety of applications are density, malleability, lubricity, flexibility, electrical conductivity, and coefficient of thermal expansion, all of which are quite high; and elastic modulus, elastic limit, strength, hardness, and melting point, all of which are quite low. Lead also has good resistance to corrosion under a wide variety of conditions. Lead is easily alloyed with many other metals and casts with little difficulty.

The high density of lead (11.35 g/cm3, at room temperature) makes it very effective in shielding against x-rays and gamma radiation. The combination of high density, high limpness (low stiffness), and high damping capacity makes lead an excellent material for deadening sound and for isolating equipment and structures from mechanical vibrations.

Malleability, softness, and lubricity are three related properties that account for the extensive use of lead in many applications.

The low tensile strength and low creep strength of lead must always be considered when designing lead components. The principal limitation on the use of lead as a structural material is not its low tensile strength but its susceptibility to creep. Lead continuously deforms at low stresses and this deformation ultimately results in failure at stresses far below the ultimate tensile strength. The low strength of lead does not necessarily preclude its use. Lead products can be designed to be self-supporting, or inserts or supports of other materials can be provided. Alloying with other metals, notably calcium or antimony, is a common method of strengthening lead for many applications. In general, consideration should always be given to supporting lead structures by lead-covered steel straps. When lead is used as a lining in a structure made of a stronger material, the lining can be supported by bonding it to the structure. With the development of improved bonding and adhesive techniques, composites of lead with other materials can be made. Composites have improved strength yet also retain the desirable properties of lead.

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Products and Applications

The most significant applications of lead and lead alloys are lead-acid storage batteries (in the grid plates, posts, and connector straps), ammunition, cable sheathing, and building construction materials (such as sheet, pipe, solder, and wool for caulking). Other important applications include counterweights, battery clamps and other cast products such as: bearings, ballast, gaskets, type metal, terneplate, and foil. Lead in various forms and combinations is finding increased application as a material for controlling sound and mechanical vibrations. Also, in many forms it is important as shielding against x-rays and, in the nuclear industry, gamma rays. In addition, lead is used as an alloying element in steel and in copper alloys to improve machinability and other characteristics, and it is used in fusible (low-melting) alloys for fire sprinkler systems.

Battery Grids. The largest use of lead is in the manufacture of lead-acid storage batteries. These batteries consist of a series of grid plates made from either cast or wrought calcium lead or antimonial lead that is pasted with a mixture of lead oxides and immersed in sulfuric acid.

Type metals, a class of metals used in the printing industry, generally consist of lead-antimony and tin alloys. Small amounts of copper are added to increase hardness for some applications.

Cable Sheathing. Lead sheathing extruded around electrical power and communication cables gives the most durable protection against moisture and corrosion damage, and provides mechanical protection of the insulation. Chemical lead, 1% antimonial lead, and arsenical lead are most commonly employed for this purpose.

Sheet. Lead sheet is a construction material of major importance in chemical and related industries because lead resists attack by a wide range of chemicals. Lead sheet is also used in building construction for roofing and flashing, shower pans, flooring, x-ray and gamma-ray protection, and vibration damping and soundproofing. Sheet for use in chemical industries and building construction is made from either pure lead or 6% antimonial lead. Calcium-lead and calcium-lead-tin alloys are also suitable for many of these applications.

Pipe. Seamless pipe made from lead and lead alloys is readily fabricated by extrusion. Because of its corrosion resistance and flexibility, lead pipes finds many uses in the chemical industry and in plumbing and water distribution system. Pipe for these applications is made from either chemical lead or 6% antimonial lead.

Solders in the tin-lead system are the most widely used of all joining materials. The low melting range of tin-lead solders makes them ideal for joining most metals by convenient heating methods with little or no damage to heat-sensitive parts. Tin-lead solder alloys can be obtained with melting temperatures as low as 182 °C and as high as 315 °C. Except for the pure metals and the eutectic solder with 63% Sn and 37% Pb, all tin-lead solder alloys melt within a temperature range that varies according to the alloy composition.

Lead-base bearing alloys, which are called lead-base babbitt metals, vary widely in composition but can be categorized into two groups:

• Alloys of lead, tin, antimony, and, in many instances, arsenic
• Alloys of lead, calcium, tin, and one or more of the alkaline earth metals

Ammunition. Large quantities of lead are used in ammunition for both military and sporting purposes. Alloys used for shot contain up to 8% Sb and 2% As; those used for bullet cores contain up to 2% Sb.

Terne Coatings. Long terne steel sheet is carbon steel sheet that has been continuously coated by various hot dip processes with terne metal (lead with 3 to 15% Sn). Its excellent solderability and special corrosion resistance make the product well-suited for this application.

Lead foil, generally known as composition metal foil, is usually made by rolling a sandwich of lead between two sheets of tin, producing a tight union of the metals.

Fusible Alloys. Lead alloyed with tin, bismuth, cadmium, indium, or other elements, either alone or in combination, forms alloys with particularly low melting points. Some of these alloys, which melt at temperatures even lower than the boiling point of water, are referred to as fusible alloys.

Anodes made of lead alloys are used in the electrowinning and plating of metals such as manganese, copper, nickel, and zinc. Rolled lead-calcium-tin and lead-silver alloys are the preferred anode materials in these applications, because of their high resistance to corrosion in the sulfuric acid used in electrolytic solutions. Lead anodes also have high resistance to corrosion by seawater, making them economical to use in systems for the cathodic protection of ships and offshore rigs.

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