Zinc is a brittle transition metal of a bluish-white color (it fades
in the air, being covered with a thin layer of zinc oxide). Zinc (Zn) is
a white silver metal (mp = 420 ° C, tkip = 906 ° C), brittle at room
temperature. When stored in air, it acquires a light bluish tint,
covered with a thin film of zinc oxide ZnO or basic carbonate 2ZnCO3 o
Zn (OH) 2, which protects it from further oxidation. Roofing iron is
covered with zinc. Pay attention to the rusted grate, which has not been
galvanized. Even if the zinc coating is damaged, the iron will still not
begin to rust until it corrodes the entire zinc coating. The bulk of the
zinc goes to cover the iron to protect it from rust. Roofing sheets,
drainpipes, buckets and many other products are made of galvanized iron.
Pure metallic zinc is used to restore the noble metals mined by underground leaching (gold, silver). In addition, zinc is used to extract silver, gold (and other metals) from crude lead in the form of zinc intermetallic compounds with silver and gold (the so-called "silver foam"), which are then processed by conventional refining methods.
It is used to protect steel from corrosion (galvanizing surfaces not subject to mechanical stress, or metallization - for bridges, tanks, metal structures).
Zinc is used as a material for the negative electrode in chemical current sources, that is, in batteries and accumulators.
Zinc plates are widely used in printing, in particular, for printing illustrations in large publications. For this, from the 19th century, zincography has been used - the production of cliches on a zinc plate by etching the pattern in it with acid. Impurities, with the exception of a small amount of lead, impair the etching process. Before etching, the zinc plate is annealed and rolled in a heated state.
Zinc is introduced into many brazing alloys to lower their melting point.
Zinc oxide is widely used in medicine as an antiseptic and anti-inflammatory agent. Zinc oxide is also used for the production of paint - zinc white.
Zinc is an important component of brass. Zinc alloys with aluminum and magnesium (TsAM, ZAMAK) due to the relatively high mechanical and very high casting qualities are very widely used in mechanical engineering for precision casting. In particular, in weaponry, ZAMAK alloys (-3, -5) sometimes cast pistol locks, especially those designed to use weak or traumatic cartridges. All kinds of technical fittings are cast from zinc alloys, such as car handles, carburetor bodies, scale models and various miniatures, as well as any other products that require precision casting with acceptable strength.
Zinc chloride is an important flux for soldering metals and a component in the manufacture of fiber.
Telluride, selenide, phosphide, zinc sulfide are widely used semiconductors. Zinc sulfide is an integral part of many phosphors. Zinc phosphide is used as a poison for rodents.
Zinc selenide is used to make optical glasses with a very low absorption coefficient in the mid-infrared range, for example, in carbon dioxide lasers.
Zinc does not exist in nature in a free state. It is obtained from their other mined ores. The main compounds that contain zinc:
polymetallic sulfide ores
minerals, most in sphalerite.
Along with zinc, small amounts of thallium, cadmium, germanium, and gallium are present in mixed ores.
Zinc is processed in special plants. Each of the enterprises is characterized by its special production technologies.
In order to isolate zinc, it is necessary to enrich the ore using a flotation or gravity method. As a result of enrichment, zinc concentrate is formed, as well as by-products, such as copper or pyrite concentrate.
This is followed by kiln firing of zinc concentrate, which results in zinc oxide. At this stage, the process is divided. The resulting sulphurous gas is transferred to create sulphurous acid, and zinc has yet another purification step.
There are two methods for producing zinc at this stage:
distillation (pyrometallurgy). Specialists bake the concentrate, sinter and recover using coal or coke. Next, metal fumes are condensed and poured into molds
electrolysis (hydrometallurgy). In this method, at the end of the firing, the concentrate is treated with sulfuric acid. The resulting solution is purified from unnecessary impurities by electrolysis .