Tin in its pure form is a metal which is silvery white, ductile, highly crystalline and malleable. Tin is seen as a green metal, and is valued for its non-toxicity and resistance to corrosion. Compared to other metals, the melting point of tin is low (at 231.93°C), while the boiling point is quite high (2062°C). This wide range makes the capacity of tin to alloy with other metals one of its most attractive features, as well as its appearance. It’s found everywhere in nature, with small amounts present in rocks, soil, plants, water, and in our bodies. The world’s foremost regulatory bodies do not list tin among the inorganic chemicals restricted for health reasons. Tin and tin alloys are excellent candidates as replacements for environmentally undesirable metals, especially lead and cadmium.
TIN IN HISTORY
Tin is one of the oldest metals known by man. There are domestic utensils and arrow-heads made of bronze (copper with about 15% of tin), dating from 3500 B.C. The Phoenicians had a very important role in the spread of bronze utensils due to its commercial trades with Britain, Spain and the Middle East. Pliny - the Roman author, naturalist, and natural philosopher - referred in 49 A.D. to the existence of tin and lead alloys, what we now know as solder, as well as recipients of tinned copper. Tinned iron was only developed in the 14th century in Bohemia, and tinned steel appeared only in the 17th century.
Tin in solder is essential in the electronics industry and until recently was an alloy of tin and lead. With a low temperature melting point, this alloy was the material that allowed the joining of all the components on a circuit board in every electronics instrument made. Every computer, mobile phone and camera has a solder join.
The lead component in solder has come under increasing environmental concern because of the amount of electronic equipment that makes its way into rubbish fill, and the toxicity in lead is seen to be draining away from these fill areas. Therefore there are mandated requirements for the increasing tin component in solder, and 90% tin component solders are the main type used in the industry today.
About 17% of tin produced today goes into making tinplated steel - tinplate - for food and beverage cans; a long established means of packaging and storing both perishable and non-perishable substances. Tinplate is a long term, well established, safe and dependable material used in the food packaging industry. It is a thin coating of tin metal on the steel cans used by the food industry that provides the non-corrosive layer which allows long term robust storage of food products from production to homes.
Tinplate was once the main global use of tin, however in the late 1970s alternatives were introduced, aluminium and plastic lined tin cans lead to the tin price collapse. Today tinplate use is steadily increasing, especially in India and China
The chemical industry is a fast growing consumer of tin. Demand is strong for household and industrial paints, in plastics, brake pads, water treatment (corrosion inhibition) applications and in non-ferrous alloys for use in engineering industries. More potential growth areas for tin chemicals were cited as fire retardants, antimicrobials - which can be disinfectants or other products used to kill microorganisms such as bacteria, fungi and protozoans - and dental products, as tin fluoride is already being used as an additive in toothpaste.
Tin is one of the two basic elements used since the Renaissance in the manufacture of organ pipes (the other being lead). The amount of tin in the pipe defines the pipe's tone, tin being the most tonally resonant of all metals. Tin mixed with copper makes bronze, which has a wide range of uses in today’s world; sculptures and ornaments, ship propellers, bearings, clips, electrical connectors, springs, guitar and piano strings and durable tools to name a few.
Combining increasing amounts of tin with copper creates an even stronger alloy called 'Gunmetal'. Originally used primarily for making guns (and in particular cannons), this use was, eventually, mostly replaced by high-grade steel. Gunmetal resists corrosion from steam and salt water. It also casts and machines well and, as such, still has a major modern use in ship propellers, steam and hydraulic castings, valves and gears as well as statues and various small objects.
Window glass is most often made via floating molten glass on top of molten tin (creating float glass) in order to make a flat surface (this is called the "Pilkington process").
Additionally, electrically conductive coatings are produced when tin salts are sprayed onto glass. These energy efficient coatings have been used in panel lighting and in the production of frost-free windshields and have little environmental impact.
New uses of tin are being discovered, particularly as a result of the ongoing research at the International Tin Research Institute Ltd (ITRI).
TIN METAL TRADING
Tin is one of the original four metals aside copper, lead and zinc that were traded on the London Metal Exchange in the late 19th century.
The LME provides the principal pricing mechanism for the tin industry, an international exchange where the sales and purchases can be hedged. Trading is in 5 tonne lots and the US dollar is the major currency in use. Traded option contracts for tin are also offered. The LME is a 24-hour market and is not restricted to the periods of floor trading.
Tin sale agreements can be negotiated whereby the mining company is paid 80% of the value of the concentrates against assay documents prior to export. The 20% balance is payable on smelter out-turn.