Lead



Lead is a main-group element with symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed to air. Lead has a shiny chrome-silver luster when it is melted into a liquid.

History
Lead has been commonly used for thousands of years because it is widespread, easy to extract and easy to work with. It is highly malleable and ductile as well as easy to smelt. Metallic lead beads dating back to 6400 BCE have been found in Çatalhöyük in modern-day Turkey. In the early Bronze Age, lead was used with antimony and arsenic. Lead is mentioned in the Book of Exodus (15:10).

The largest preindustrial producer of lead was the Roman economy, with an estimated output per annum of 80,000 t, which was typically won as a by-product of silver smelting. Roman mining activities occurred in Central Europe, Roman Britain, the Balkans, Greece, Asia Minor; Hispania alone accounted for 40% of world production.

Roman lead pipes often bore the insignia of Roman emperors (see Roman lead pipe inscriptions). Lead plumbing in the Latin West may have been continued beyond the age of Theoderic the Great into the medieval period. Many Roman "pigs" (ingots) of lead figure in Derbyshire lead mining history and in the history of the industry in other English centers. The Romans also used lead in molten form to secure iron pins that held together large limestone blocks in certain monumental buildings. In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Alchemists accordingly used Saturn's symbol (the scythe, ♄) to refer to lead.

Lead's symbol Pb is an abbreviation of its Latin name plumbum for soft metals; originally it was plumbum nigrum (literally, "black plumbum"), where plumbum candidum (literally, "bright plumbum") was tin. The English words "plumbing", "plumber", "plumb", and "plumb-bob" also derive from this Latin root.

Cleaning
-very soft metal,not recommended
 * Mechanical


 * Chemical

1.Hydrochloric acid/Ammonium acetate treatment

Solution A: 5% HCl

Solution B: 10% ammonium acetate,with 0,2% agar agar

Solution A removes all except oxide,after that step rinse in hot destilled water,and then remove any oxide with solution B. Rinse with cold destilled water. Solution B can be used without solution A.

2.EDTA solution

40 gm EDTA

1 lit water

pH must be 5-5,5

Immerse object in solution. Specially good for basic lead carbonate removal. Hot solution work faster(80 C). Rinse with hot destilled water.

3.Alkaline solution

200 gm slaked lime

100 gm Na2CO3

50 gm NaOH

Add small amount of water,result must be thick liquid!

Removes lead carbonate,sulphate and oxide.Rinse well with destilled water.


 * Electrochemical

Electrolytic cleaning

5% NaOH or Na2CO3

stainless steel anodes

10-12 v,2-5A/dm2

Object connected to negative terminal of current source must be immersed in solution,anode must be immersed before. First rinse in diluted sulphuric acid(pH 3,5),then in destilled water.


 * Ultrasonic


 * Laser

Structural consolidation

 * Mecanical joning
 * Soldering
 * Welding
 * Gluing/cementing

Stabilization

 * Corrosion inhibitors
 * Conversion coatings

Clearcoats

 * Paraloid B 72
 * Paraloid B 67
 * Paraloid B 44
 * Paraloid B 48 N

Waxes

 * Renaissance Wax
 * Cosmolloid 80 H
 * DIY mixtures

Combinations

 * basecoat Paraloid B 72 + topcoat Renaissance wax etc.