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Zinc is a moderately reactive, blue gray metal that tarnishes in moist air and burns in air with a bright bluish-green flame, giving off fumes of zinc oxide. It reacts with acids, alkalis and other non-metals. If not completely pure, zinc reacts with dilute acids to release hydrogen. The one common oxidation state of zinc is +2. From 100 °C to 210 °C (212 °F to 410 °F) zinc metal is malleable and can easily be beaten into various shapes. Above 210 °C (410 °F), the metal becomes brittle and will be pulverized by beating. Zinc is nonmagnetic. The earth has been estimated to have 46 years supply of zinc. There are zinc mines throughout the world, with the largest producers being China, Australia and Peru. In 2005, China produced almost one-fourth of the global zinc output, reports the British Geological Survey. Mines and refineries in Europe include Umicore in Belgium, Tara, Galmoy and Lisheen in Ireland and Zinkgruvan in Sweden. Zinc metal is produced using extractive metallurgy. Zinc sulfide (sphalerite) minerals are concentrated using the froth flotation method and then usually roasted using pyrometallurgy to oxidise the zinc sulfide to zinc oxide. The zinc oxide is leached to zinc sulfate (ZnSO4) in several stages of increasingly stronger sulfuric acid (H2SO4). Iron is usually rejected as jarosite or goethite, removing other impurities at the same time. The final purification uses zinc dust to remove copper, cadmium and cobalt in two to three different stages. The metal is then extracted from the purified zinc sulfate solution by electrowinning as cathodic deposits over aluminium sheets. Zinc cathodes can be directly cast or alloyed with aluminium. Electrolyte zinc sulfate solutions must be very pure for electrowinning to be at all efficient. Impurities can change the decomposition voltage enough to where the electrolysis cell produces largely hydrogen gas rather than zinc metal.[40] There are two common processes for electrowinning the metal: the low current density process, and the Tainton high current density process. The former uses a 10% sulfuric acid solution as the electolyte, with current density of 270–325 amperes per square meter. The latter uses 22–28% sulfuric acid solution as the electrolyte with a current density of about 1,000 amperes per square meter. The latter gives better purity and has higher production capacity per volume of electrolyte, but has the disadvantage of running hotter and being more corrosive to the vessel in which it is done. In either of the electrolytic processes, each metric ton of zinc production expends about 3900 kW•h (14 MJ) of electric power. There are also several pyrometallurgical processes that reduce zinc oxide using carbon, then distill the metallic zinc from the resulting mix in an atmosphere of carbon monoxide. These include the Belgian-type horizontal-retort process, the New Jersey Zinc continuous vertical-retort process, and the St. Joseph Lead Company's electrothermal process. The Belgian process requires redistillation to remove impurities of lead, cadmium, iron, copper, and arsenic. The New Jersey process employs a fractionating column, which is absent in the Belgian process, that separates the individual impurities, where they can be sold as byproducts. The St. Joseph Lead Company process heats the zinc oxide/coke mixture by passing an electric current through it rather than by coal or gas fire. Another pyrometallurgical process is flash smelting. Then zinc oxide is obtained, usually producing zinc of lesser quality than the hydrometallurgical process. Zinc oxide treatment has much fewer applications, but high grade deposits have been successful in producing zinc from zinc oxides and zinc carbonates using hydrometallurgy. The most widely used alloy of zinc is brass, in which copper is alloyed with anywhere from 9% to 45% zinc, depending upon the type of brass, along with much smaller amounts of lead and tin. Alloys of 85–88% zinc, 4–10% copper, and 2–8% aluminium find limited use in certain types of machine bearings. Alloys of primarily zinc with small amounts of copper, aluminium, and magnesium are useful in die casting as well as spin casting. An example of this is zinc aluminium. Similar alloys with the addition of a small amount of lead can be cold-rolled into sheets. An alloy of 96% zinc and 4% aluminium is used to make stamping dies for low production run applications where ferrous metal dies would be too expensive. Zinc oxide is perhaps the best known and most widely used zinc compound, as it makes a good base for white pigments in paint. It also finds industrial use in the rubber industry, and is sold as opaque sunscreen. A variety of other zinc compounds find use industrially, such as zinc chloride (in deodorants), zinc pyrithione (anti-dandruff shampoos), zinc sulfide (in luminescent paints), and zinc methyl or zinc diethyl in the organic laboratory. Roughly one quarter of all zinc output is consumed in the form of zinc compounds. Naturally occurring zinc is composed of the 5 stable isotopes 64Zn, 66Zn, 67Zn, 68Zn, and 70Zn with 64Zn being the most abundant (48.6% natural abundance). Twenty-one radioisotopes have been characterised with the most abundant and stable being 65Zn with a half-life of 244.26 days, and 72Zn with a half-life of 46.5 hours. All of the remaining radioactive isotopes have half-lives that are less than 14 hours and the majority of these have half lives that are less than 1 second. This element also has 4 meta states. Zinc has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of isotopically enriched 64Zn, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope Zn-65 with a half-life of 244 days and produce approximately 2.27 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several days. Such a weapon is not known to have ever been built, tested, or used. Zinc is the fourth most common metal in use, trailing only iron, aluminium, and copper in annual production Zinc is used to galvanize steel to prevent corrosion Zinc is used to Parkerize steel to prevent rust and corrosion Zinc is used in alloys such as brass, nickelled silver, typewriter metal, various soldering formulas and German silver Zinc is the primary metal used in making American cents since 1982 Zinc is used in die casting notably in the automobile industry Zinc is used as part of the containers of batteries. The most widespread such use is as the anode in alkaline batteries Zinc is used as the anode or fuel of the zinc-air battery/fuel cell providing the basis of the theorised zinc economy Zinc is used as a sacrificial anode on boats and ships that use cathodic protection to prevent corrosion of metals that are exposed to sea water Zinc is used in contemporary pipe organ building as a substitute for the classic lead/tin alloy in pipes sounding the lowest (pedal) tones, as it is tonally almost indistinguishable from lead/tin at those pitches, and has the added advantages of being much more economical and lighter in weight. Even the best organ builders use zinc in this capacity. Zinc oxide is used as a white pigment in watercolours or paints, and as an activator in the rubber industry. As an over-the-counter ointment, it is applied as a thin coating on the exposed skin of the face or nose to prevent dehydration of the area of skin. It can protect against sunburn in the summer and windburn in the winter. Applied thinly to a baby's diaper area (perineum) with each diaper change, it can protect against rash. As determined in the Age-Related Eye Disease Study, it is part of an effective treatment for age-related macular degeneration in some cases Zinc chloride is used as a deodorant and can also be used as a wood preservative Zinc sulfide is used in luminescent pigments such as on the hands of clocks and other items that glow in the dark. Zinc methyl (Zn(CH3)2) is used in a number of organic syntheses. Zinc stearate is a lubricative plastic additive. Lotions made of calamine, a mix of Zn-(hydroxy-)carbonates and silicates, are used to treat skin rash. Zinc metal is included in most single tablet over-the-counter daily vitamin and mineral supplements. It is believed to possess anti-oxidant properties, which protect against premature aging of the skin and muscles of the body. In larger amounts, taken as zinc alone in other proprietaries, it is believed by some to speed up the healing process after an injury. Preparations include zinc acetate and zinc gluconate. Zinc gluconate glycine and zinc acetate are also used in throat lozenges or tablets to reduce the duration and the severity of cold symptoms. The graph below shows the use of zinc by end use.
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