Interesting Facts About Lead and its Various Alloys
Lead (Pb) is a bluish-white soft lustrous metal, which is highly ductile, malleable and a comparatively poor conductor of electricity. Lead is an extremely valuable metal, but due to its toxicity, it can only be used in limited applications. If humans did not have to be concerned about inhaling in lead dust or swallowing its fragments, it would have been used extensively due to its extremely industry-friendly features, such as brilliant malleability and resistance to corrosion.
Throughout the past, prior to scientific innovations uncovered its compelling deadliness, lead was extensively used in several products, including paint, cosmetics, pipes, gasoline, and solder. Certain features of lead, such as its ductility and resistance to corrosion, make it an especially excellent material for producing water pipes.
Lead is no longer used for many of its earlier uses, but this metal is quite beneficial in products that are used to keep extremely acidic materials. For instance, lead is used in tank linings that hold corrosive fluids, such as sulfuric acid. It is also applied in lead-acid batteries, found in automobiles.
Due to its ability to soak up vibration and density, lead also acts as an exceptional defense against various types of dangerous radiation, such as those found in nuclear reactors and X-ray machines. Lead is also used in some ammunition and bullets.
Lead’s low strength does not essentially prohibit its use. Products made using lead are intended to be self-supporting or inserts of other substances can be offered. Alloying with other non-ferrous metals, especially antimony or calcium, is a popular technique of bolstering lead for different applications. Generally, consideration must be given to supporting lead constructions by lead-coated steel straps. When lead is the substance used as a lining in a formation made of a tougher material, the lining can be supported by binding it to the formation.
Grades of Lead
There are four different types of lead grades, Pure lead, which is also known as corroding lead, Common lead, Chemical lead and Acid-copper lead. Corroding lead and common lead both contain a minimum of 99.94% lead while chemical lead and acid-copper lead contain 99.90% lead. Lead of superior stipulated purity (99.99%) is also obtainable in industrial capacities.
Chemical Lead: Refined lead with an enduring silver content of 0.002% to 0.02% and a lingering copper content of 0.04% to 0.08% is especially popular in chemical industries and consequently is termed chemical lead.
Corroding Lead: Most lead manufactured worldwide is pure or corroding lead. Corroding lead demonstrates excellent corrosion resistance characteristic of lead and its alloys. Corroding lead is used in formulating lead oxides and pigments and a wide array of other lead chemicals.
Copper-bearing lead offers protection from corrosion, which is similar to that of chemical lead in nearly all applications that entail high resistance to corrosion. Common lead, which comprises greater volumes of bismuth and silver than corroding lead, is used for general alloying and battery oxide.
Properties of Lead
The characteristics of lead that makes it useful in various applications are malleability, density, flexibility, lubricity, coefficient of thermal expansion, and electrical conductivity all of which are on the higher side. It also has features such as elastic limit, elastic modulus, hardness, melting point, and strength that are all quite low. Lead can also be easily alloyed with several other casts and metals with little trouble.
Lead’s high density makes it an effective substance as a guard against gamma and x-ray radiation. The blend of high limpness, high density, and high damping capacity makes lead an exceptional substance for stifling sound and for insulating structures and equipment from vibrations.
Softness, lubricity, and malleability are three correlated features that account for the widespread use of lead in multiple applications.
The low creep strength and low tensile strength of lead must always be taken into account when building lead components. The primary limitation of using lead as a structural substance is not its minimal tensile strength but its vulnerability to creep. Lead unceasingly distorts at low stresses and this distortion eventually leads to failure at stresses much below the definitive tensile strength.
With the advancement of enhanced adhesive and bonding techniques, combinations of lead with other substances can be made. Combinations have enhanced strength yet also keep hold of the desirable characteristics of lead.
Alloys of Lead
Since lead is ductile and soft, it is typically used as lead alloys commercially. Tin, antimony, calcium, and arsenic are some of the commonly used alloying elements. Antimony provides better strength and hardness, as in battery grids, pipe, castings, and sheet. The amount of antimony in lead-antimony alloys ranges from 0.5% to 25% but normally hovers around 2% to 5%.
Today lead-calcium alloys are more widely used in comparison to lead-antimony alloys in several applications, particularly with casting applications and battery grids. The amount of calcium in these alloys varies from 0.03% to 0.15%. Lately, aluminium is also added as a stabilizer for calcium in calcium-lead and calcium-tin-lead alloys. Adding tin to lead or lead alloys improves strength and hardness, but lead-tin alloys are utilized for their excellent casting, wetting, and melting properties.
Tin gives the alloy the power to wet and bind with metals such as copper and steel. Unalloyed lead has inadequate wetting qualities. Tin fused with bismuth and lead, or cadmium forms the key ingredient of numerous low-melting alloys.
Arsenical lead is utilized for sheathing cables. Arsenic is frequently used to solidify lead-antimony alloys and is critical to the creation of round dropped shot.
Impact of Lead on Human Health
Lead is one of the four metals with the most dangerous effects on humans. It can enter our bodies through food, air, and water. Food items such as vegetables, meat, seafood, wine, and soft drinks could possibly have substantial amounts of lead.
Lead can enter the water through corroded pipes. That is why community water treatment plants are now needed to carry out pH adjustments in water. Lead can cause numerous undesirable effects, such as:
● Behavioral disturbances in children, such as impulsive behavior, hyperactivity, and aggression
● Reduced learning abilities among children
● Weakened fertility among men as a result of sperm damage
● Brain and kidney damage
● Disruption of nervous systems
Environmental Consequences of Lead
In addition to leaded gasoline, other human actions, such as industrial manufacturing, solid waste combustion, and fuel combustion also increase lead concentrations in the environment.
Lead ends up in the water and pollutes the soil through lead corroded pipelines for transporting water and through the corrosion of leaded paints. The pollutants cannot be broken down and they can only be transformed into other forms.
Lead collects in the bodies of organisms in soil and water. It eventually, affects the health of shellfish and phytoplankton even when only small concentrations of lead are present.
Phytoplankton is a key source of oxygen production in oceans and many large sea animals consume it. That is why it is believed that lead pollution can impact global balances.
Soil functions are disrupted by the accumulation of lead, especially near farmlands and highways, where excessive concentrations may be present. Organisms in the soil suffer from lead poisoning, too. Lead is a dangerous chemical, as it can not only accumulate in individual organisms, but also in the whole food chain.