Zinc is a bluish-white, reactive metal whose tonnage is far below that of iron, steel and copper, yet it plays a steady role in three fields: corrosion protection, alloys and batteries. Its largest use is hot-dip galvanizing: steel sheet or wire is dipped in molten zinc to form a dense zinc layer that sacrificially protects the steel when corrosion begins, so galvanized sheet, pipe and fittings are widely used on roofing panels, highway guardrails, lampposts and transmission towers, making galvanizing the dominant anti-corrosion route for steel worldwide. Brass, a copper-zinc alloy, combines the workability of copper with the strength and wear resistance of zinc and is used in taps, valves, locks, musical instruments and decorative hardware. In batteries, zinc-carbon and alkaline zinc-manganese cells use zinc as the negative can or gel anode in enormous volumes, while zinc-air and zinc-bromine flow batteries are hot topics in energy-storage research. Zinc also goes into die-casting alloys (precision die castings for cars and home appliances), metallurgical reducing agents, and raw materials for pesticides and pharmaceuticals.
ZnS, i.e. sphalerite, is the main ore for zinc smelting; after flotation it is roasted to zinc oxide, from which metallic zinc is extracted by hydrometallurgical or pyrometallurgical routes. Zinc oxide (ZnO), a widely used white powder known as zinc white, acts as a vulcanization activator in rubber tires, as a white pigment in plastics and paints, as a UV absorber in sunscreens, and as a raw material for electronic ceramics such as varistors. Zinc sulfate (ZnSO4) is used as a trace zinc additive in animal feed and crop fertilizers, and also in viscose-fiber spinning baths and electroplating. Zinc chloride (ZnCl2) is a main constituent of soldering flux, a wood preservative and a battery electrolyte, and is also used medicinally as an astringent and deodorant.
