Physical and chemical properties of zinc. zinc metal
It is located in the second group, a side subgroup of the periodic system of Mendeleev and is a transition metal. The serial number of the element is 30, the mass is 65.37. The electronic configuration of the outer layer of the atom is 4s2. The only and constant is "+2". Transition metals are characterized by the formation of complex compounds in which they act as a complexing agent with different coordination numbers. This also applies to zinc. There are 5 naturally stable isotopes with mass numbers from 64 to 70. At the same time, the 65Zn isotope is radioactive, its half-life is 244 days.
Zinc is a silvery-blue metal that rapidly develops a protective oxide film when exposed to air, hiding its luster. When the oxide film is removed, zinc exhibits the properties of metals - radiance and a characteristic bright luster. In nature, zinc is found in many minerals and ores. The most common: cleophane, zinc blende (sphalerite), wurtzite, marmatite, calamine, smithsonite, willemite, zincite, franklinite.
Smithsonite
As part of mixed ores, zinc occurs with its constant companions: thallium, germanium, indium, gallium, cadmium. The earth's crust contains 0.0076% zinc, and 0.07 mg / l of this metal is found in sea water in the form of salts. The formula of zinc as a simple substance is Zn, the chemical bond is metallic. Zinc has a hexagonal dense crystal lattice.
Physical and chemical properties of zinc
The melting point of zinc is 420 °C. Under normal conditions, it is a brittle metal. When heated to 100-150 ° C, the ductility and ductility of zinc increases, it is possible to manufacture wire from metal and roll foil. The boiling point of zinc is 906 °C. This metal is an excellent conductor. Starting from 200 °C, zinc is easily triturated into a gray powder and loses plasticity. The metal has good thermal conductivity and heat capacity. The described physical parameters allow the use of zinc in compounds with other elements. Brass is the best known zinc alloy.
Brass wind instruments
Under normal conditions, the surface of zinc is instantly covered with oxide in the form of a gray-white dull coating. It is formed due to the fact that oxygen in the air oxidizes a pure substance. Zinc as a simple substance reacts with chalcogens, halogens, oxygen, alkalis, acids, ammonium (its salts),. Zinc does not interact with nitrogen, hydrogen, boron, carbon and silicon. Chemically pure zinc does not react with solutions of acids and alkalis. - the metal is amphoteric, and when reacting with alkalis, it forms complex compounds - hydroxozincates. Click to find out what experiments on the study of the properties of zinc can be done at home.
The reaction of sulfuric acid with zinc and the production of hydrogen
The interaction of dilute sulfuric acid with zinc is the main laboratory method for producing hydrogen. For this, pure grained (granular) zinc or technical zinc in the form of scraps and shavings is used.
If very pure zinc and sulfuric acid are taken, then hydrogen is released slowly, especially at the beginning of the reaction. Therefore, a little solution of copper sulphate is sometimes added to the solution that has cooled down after dilution. Metallic copper deposited on the zinc surface speeds up the reaction. The best way to dilute acid to produce hydrogen is to dilute concentrated sulfuric acid with a density of 1.19 with water in a ratio of 1:1.
Reaction of concentrated sulfuric acid with zinc
In concentrated sulfuric acid, the oxidizing agent is not a hydrogen cation, but a stronger oxidizing agent, the sulfate ion. It does not show itself as an oxidizing agent in dilute sulfuric acid due to strong hydration, and, as a result, low mobility.
How concentrated sulfuric acid will react with zinc depends on temperature and concentration. Reaction equations:
Zn + 2H₂SO₄ = ZnSO₄ + SO₂ + 2H₂O
3Zn + 4H₂SO₄ = 3ZnSO₄ + S + 4H₂O
4Zn + 5H₂SO₄ = 4ZnSO₄ + H₂S + 4H₂O
Concentrated sulfuric acid is a strong oxidizing agent due to the oxidation state of sulfur (S⁺⁶). It interacts even with low-activity metals, that is, with metals before and after hydrogen, and, unlike dilute acid, it never releases hydrogen during these reactions. In the reactions of concentrated sulfuric acid with metals, three products are always formed: salt, water, and the product of sulfur reduction. Concentrated sulfuric acid is such a strong oxidizing agent that it even oxidizes some non-metals (coal, sulfur, phosphorus).
The element zinc (Zn) in the periodic table has serial number 30. It is in the fourth period of the second group. Atomic weight - 65.37. Distribution of electrons in layers 2-8-18-2
The origin of the element's name is unclear, but it seems plausible that it is derived from Zinke (German for "point" or "tooth"), due to the appearance of the metal.
Zinc is a bluish-white metal, melting at 419 C, and turning into steam at 913 C; its density is 7.14 g/cm3. At ordinary temperatures, zinc is rather brittle, but at 100-110 C it bends well and rolls into sheets. In air, zinc is covered with a thin layer of oxide or basic carbonate, which protects it from further oxidation.
Water has almost no effect on zinc, although it is in the series of voltages much to the left of hydrogen. This is explained by the fact that the hydroxide formed on the surface of zinc during its interaction with water is practically insoluble and prevents the further course of the reaction. In dilute acids, however, zinc readily dissolves to form the corresponding salts.
In addition, zinc, like beryllium and other metals that form amphoteric hydroxides, dissolves in alkalis. If zinc is heated in air to the boiling point, then its vapor ignites and burns with a greenish-white flame, forming zinc oxide.
When heated, zinc interacts with non-metals (except hydrogen, carbon and nitrogen). Actively reacts with acids:
Zn + H2SO4 (dec.) = ZnSO4 + H2
Zinc is the only element of the group that dissolves in aqueous solutions of alkalis with the formation of ions (hydroxozincates):
Zn + 2OH + 2H2O = + H2
Physical properties of zinc. Zinc is a medium hard metal. In a cold state, it is brittle, and at 100-150 ° C it is very plastic and easily rolled into sheets and foil with a thickness of about hundredths of a millimeter. At 250°C it becomes brittle again. It has no polymorphic modifications. It crystallizes in a hexagonal lattice with parameters a = 2.6594Å, c = 4.9370Å. Atomic radius 1.37Å; ionic Zn2+ -0.83Å. The density of solid zinc is 7.133 g/cm3 (20°C), liquid zinc is 6.66 g/cm3 (419.5°C); mp 419.5 °С; bp 906 °С. Thermal coefficient of linear expansion 39.7 10-3 (20-250 °C), thermal conductivity coefficient 110.950 W/(m K) 0.265 cal/cm sec °C (20 °C), electrical resistivity 5.9 10-6 ohm cm (20 °C), specific heat capacity of Zinc 25.433 kJ/(kg K.) . Tensile strength 200-250 MN/m2 (2000-2500 kgf/cm2), relative elongation 40-50%, Brinell hardness 400-500 MN/m2 (4000-5000 kgf/cm2). Zinc is diamagnetic, its specific magnetic susceptibility is -0.175 10-6.
Chemical properties of zinc. The external electronic configuration of the Zn atom is 3d104s2. The oxidation state in compounds is +2. The standard electrode potential equal to -0.76 V characterizes Zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 ° C, zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In humid air, especially in the presence of CO2, metal is destroyed even at ordinary temperatures. When strongly heated in air or in oxygen, zinc burns intensely with a bluish flame with the formation of white smoke of zinc oxide ZnO. Dry fluorine, chlorine and bromine do not interact with Zinc in the cold, but in the presence of water vapor the metal can ignite, forming, for example, ZnCl2. A heated mixture of zinc powder with sulfur gives zinc sulfide ZnS. Zinc sulfide precipitates under the action of hydrogen sulfide on slightly acidic or ammoniac aqueous solutions of Zn salts. The ZnH2 hydride is obtained by the interaction of LiAlH4 with Zn(CH3)2 and other Zinc compounds; metal-like substance that decomposes into elements when heated. Nitride Zn3N2 - black powder, formed when heated to 600 ° C in a stream of ammonia; stable in air up to 750 °C, water decomposes it. Zinc carbide ZnC2 was obtained by heating Zinc in a stream of acetylene. Strong mineral acids vigorously dissolve Zinc, especially when heated, to form the corresponding salts. When interacting with dilute HCl and H2SO4, H2 is released, and with HNO3 - in addition, NO, NO2, NH3. Zinc reacts with concentrated HCl, H2SO4, and HNO3, releasing H2, SO2, NO, and NO2, respectively. Solutions and melts of alkalis oxidize zinc with the release of H2 and the formation of water-soluble zincites. The intensity of the action of acids and alkalis on Zinc depends on the presence of impurities in it. Pure Zinc is less reactive with respect to these reagents due to the high overvoltage of hydrogen on it. In water, zinc salts hydrolyze when heated, releasing a white hydroxide precipitate.
a) reaction of zinc with dilute acids
Zn(OH)2. H2SO4 + Zn = ZnSO4 + H2
Zinc, as an active metal, can form sulfur dioxide, elemental sulfur, and even hydrogen sulfide with concentrated sulfuric acid.
2H2SO4 + Zn = SO2 + ZnSO4 + 2H2O
When zinc reacts with very dilute nitric acid, ammonia is released, which reacts with an excess of acid to form ammonium nitrate.
Zinc does not appear in nature as a native metal. Zinc is mined in two ways:
1) pyrometallurgical method
2) hydrometallurgical method from polymetallic ores containing 1-4% Zn in the form of sulfide, as well as Cu, Pb, Ag, Au, Cd, Bi. Ores are enriched by selective flotation, obtaining zinc concentrates (50-60% Zn) and simultaneously lead, copper, and sometimes also pyrite concentrates. Zinc concentrates are fired in fluidized bed furnaces, converting zinc sulfide into ZnO oxide; the resulting sulfur dioxide SO2 is used to produce sulfuric acid. There are two routes from ZnO to Zn.
1) According to the pyrometallurgical (distillation) method, which has existed for a long time, the calcined concentrate is sintered to give grain size and gas permeability, and then reduced with coal or coke at 1200 - 1300 ° C:
ZnO + C = Zn + CO.
The resulting metal vapors are condensed and poured into molds. At first, the restoration was carried out only in hand-operated fired clay retorts; later, vertical mechanized carborundum retorts began to be used, then - shaft and electric arc furnaces; from lead-zinc concentrates, zinc is obtained in shaft furnaces with blast. Productivity gradually increased, but zinc contained up to 3% impurities, including valuable cadmium. Distillation zinc is purified by segregation (that is, by settling the liquid metal from iron and part of lead at 500 ° C), reaching a purity of 98.7%. The sometimes more complex and expensive purification by rectification, which is sometimes used, gives a metal with a purity of 99.995% and allows the extraction of cadmium.
The main method of obtaining zinc is electrolytic (hydrometallurgical). Calcined concentrates are treated with sulfuric acid; the resulting sulfate solution is purified from impurities (by deposition with zinc dust) and subjected to electrolysis in baths tightly lined inside with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from which it is daily removed (stripped off) and melted in induction furnaces. Usually the purity of electrolytic zinc is 99.95%, the completeness of its extraction from the concentrate (taking into account waste processing) is 93-94%. Production wastes produce zinc sulfate, Pb, Cu, Cd, Au, Ag; sometimes also In, Ga, Ge, Tl.
2) The hydrometallurgical method of processing calcined zinc concentrates consists in dissolving zinc oxide with an aqueous solution of sulfuric acid and subsequent precipitation of zinc by electrolysis. Therefore, the hydrometallurgical method is sometimes called electrolytic. In the production of zinc by electrolysis, the zinc concentrate is preliminarily subjected to oxidative roasting.
ZnSO4 → Zn 2+ + SO4 2-
2+ (–) cathode Zn , H2O (+) anode: SO42–, H2O
Zn + 2e Zn 2H2O – 4e O2 + 4H+
2H2O + 2e H2 + 2HO
Summary Equation
ZnSO4 + 2H2O Zn + H2 + O2 + H2SO4.
The resulting cinder is leached with a spent electrolyte containing sulfuric acid. The resulting solution of zinc sulfate is purified from harmful impurities and sent for electrolysis. In this case, zinc is deposited on the cathode, and sulfuric acid is regenerated in the solution, which is returned again for leaching.
If the roasting of the zinc concentrate precedes the leaching, then the goal is to convert the zinc sulfide as completely as possible into zinc oxide, which is soluble in dilute solutions of sulfuric acid.
The leaching of the cinder is carried out with a spent electrolyte containing sulfuric acid and obtained by electrolysis of a zinc solution. In the process of redistribution, losses of sulfuric acid are inevitable (both mechanical, occurring due to the loss of the solution, and chemical, caused by the fact that sulfuric acid is unproductively spent on the dissolution of impurities). These losses are replenished by the fact that a certain amount of zinc sulfate, which is easily soluble in water, is obtained in the cinder. For this purpose, it is enough to have about 2-4% sulfate sulfur in the calcined concentrate.
About 70% of the world's zinc production is obtained in this way. This is explained by the fact that the electrolytic method, with good mechanization of labor-intensive processes and a high percentage of extraction, produces zinc that is purer than by distillation. In addition, the possibility of complex use of valuable components of the concentrate is facilitated. To isolate zinc, the ZnS concentrate obtained after enrichment is subjected to roasting:
2ZnS+3O2→ 2ZnO+2SO2
In general:
4Zn + 10HNO3 = 4Zn(NO3)2 + NH4NO3 + 3H2O
Zn + HNO3 = Zn(NO3)2 + NO + H2O
b) Interaction of soluble zinc salts with alkalis:
ZnCl2 +2NaOH= ZnOH2↓+2NaCl
Zn(NO3)2+2KOH = ZnOH2↓ +2KNO3
Zinc is an element of the periodic system 2 subgroups 4 periods with atomic number 30 and atomic weight 65.39.
Brittle transition metal zinc.
- The chemical properties of zinc are directly influenced by its relation to the block of d-elements. This group forms chemical bonds only with the outer electrons of the d-orbital. Therefore, the element has a characteristic oxidation state of +2 and similarity with the properties of magnesium.
- The hexagonal lattice of zinc was described as early as in Switzerland in the 16th century and was referred to as "crystal needles". The transition metal in its varieties has many isotopes. The most stable of the radioactive ones is 65 zn with a half-life of 245 days.
- Zinc metal under normal conditions is a brittle substance. Its density is 7.13 g/cm³. In the light, the luster inherent in all metals casts a bluish-gray color. The melting point starts at 46°C and the boiling point starts at 906°C. Showing amphoteric properties, the element is inferior in activity only to alkaline earth metals. The redox potential is 0.76 V.
Zinc is a corrosion resistant metal. In the pH range of pH 9–11, maximum stability is observed. Under atmospheric conditions, corrosion does not occur due to the appearance of a protective film on the surface - zinc oxide. Corrosion will take place using hydrogen or oxygen depolarization.
Role in metallurgy
Hydro- and pyrometallurgical processes are the most common ways to produce zinc metal from ore. In its properties, it is in no way inferior to chromium as an anti-corrosion coating. Half of all zinc produced is spent precisely on the application of a protective layer for iron and steel.
Anti-corrosion application of zinc.
Due to the low melting point of zinc and its alloys with other metals, there is a problem of sensitivity to overheating. Therefore, excessive overheating in production causes a disruption in the process with subsequent oxidation of the alloy. The most common are alloys with copper (brass), as well as with lead. They are widely used in engineering, alkaline batteries, galvanic cells and alloys with other noble metals.
The characteristic of the properties of an element changes under the influence of impurities. For example: the triple eutectic of an alloy of lead and zinc with an admixture of tin melts much easier than zinc itself and collapses under hot pressure. The addition of only 0.2% iron to the composition of zinc increases its brittleness several times. Bismuth and arsenic, sparingly soluble in the element, generally have a negative effect on the technological characteristics of the resulting substance.
In industry, the reducing properties of an element have an important function. He takes part in the precipitation of gold from solutions, in the production of hydrosulfite, in the extraction of copper and cadmium from ore.
Reactions with elements
Interaction with acids
The good reaction of zinc with most acids is due to its position in relation to hydrogen in the electrochemical series of activity of metals. This forms many important zinc salts. These salts are predominantly colorless, they are hygroscopic crystals, the solutions of which, due to hydrolysis, have an acidic environment. In the case of salts of other metals, it will also displace them from solution if they are in the voltage row to the right of the element.
When interacting with acids, zinc salts are formed.
In a solution of an element with sulfuric acid at a temperature below 38 ° C, zinc sulfate is formed, the scientific name of which is ZnSO4 sulfate. It is used in the production of viscose, some branches of metallurgy, in medicine as a disinfectant. ZnCl2 chloride is obtained from a solution of hydrochloric acid with zinc. It is used in the manufacture of batteries, antiseptic impregnation of wood and paper fibers.
Derived compounds
- Zinc and its amphoteric properties are transferred to zinc hydroxides Zn(OH)2. These substances are inherent in the chemical behavior of acids and bases at the same time. Hydroxide can be obtained in the form of a white precipitate by the action of alkali on sulfate. In its natural state, hydroxide is a crystalline substance that decomposes at temperatures above 130 °C. It is used for the synthesis of zinc salts.
- The old method of extracting ZnO oxide, previously referred to as the "French process", can be called spectacular. In the presence of highly heated air around the cell plate, zinc vapor will begin to evolve, which then ignites with a bluish light, forming an oxide. In large-scale production, it is mined from the natural mineral zincite. In addition, thermal decomposition of more complex compounds, such as hydroxide, is widely used to produce oxide.
- Colorless white oxide powder, insoluble in water, expresses its chemical duality. When zinc oxide is fused with alkalis, zincates are obtained. When fused with oxides - silicates. Its own thermal conductivity allows it to be a semiconductor, the band gap of which is 3.36 eV. Oxide has a wide range of applications in the chemical industry, becoming a filler in many plastics. In electronics, not a single ray tube of a TV can do without it. It is also found in most dermatological ointments.
The external electronic configuration of the Zn atom is 3d104s2. The oxidation state in compounds is +2. The normal redox potential of 0.76 V characterizes zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 ° C, zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In moist air, especially in the presence of CO2, metal is destroyed with the formation of basic zinc bicarbonate even at ordinary temperatures.
At a temperature of red heat, it can be oxidized by water vapor with the release of hydrogen and carbon dioxide. When heated sufficiently in air, it burns with a bright greenish-blue flame to form zinc oxide with a significant release of energy.
In accordance with the place occupied by zinc in the series of voltages, it readily dissolves in dilute acids with evolution of hydrogen. In this case, concentrated acid is reduced to nitrogen oxides, diluted acid is reduced to ammonia. Dissolution in conc. H3S04 is accompanied by the release of not hydrogen, but sulfur dioxide.
A mixture of zinc powder and sulfur reacts explosively when heated.
Zinc does not interact with nitrogen even in vapors, but rather easily reacts with ammonia at a red-hot temperature, forming zinc nitride - Zn3Na.
Zinc carbide ZnC, formed by heating zinc in a stream of acetylene, decomposed by water and dilute acids.
When metallic zinc is heated in phosphorus vapor to 440–780°C, phosphides, Zn3Ps and ZnP2, are formed.
In the molten state, zinc is infinitely miscible with many metals: Cu, Ag, Au, Cd, Hg, Ca, Mg, Mn, Fe, Co, Ni, Al, Sn.
Zinc forms compounds with many metals, for example: Cu, Ag, Au, Mn, Fe, Co, Ni, Pf, Pd, Rh, Sb, Mg, Ca, Li, Na, K.
Zinc is quite easily soluble in alkalis, as well as aqueous solutions of ammonia and ammonium chloride, especially when heated. The rate of dissolution of zinc not only in alkalis, but also in acids depends on its purity. Very pure zinc dissolves slowly, and to speed up the process, it is recommended to introduce a few drops of a highly dilute solution of copper sulfate into the solution (the appearance of galvanic couples).
Interaction with non-metals
When strongly heated in air, it burns with a bright bluish flame to form zinc oxide:
When ignited, it reacts vigorously with sulfur:
It reacts with halogens under normal conditions in the presence of water vapor as a catalyst:
Zn + Cl2 = ZnCl2
Under the action of phosphorus vapor on zinc, phosphides are formed:
Zn + 2P = ZnP2 or
3Zn + 2P = Zn3P2
Zinc does not interact with hydrogen, nitrogen, boron, silicon, carbon.
Interaction with water
Reacts with water vapor at red heat to form zinc oxide and hydrogen:
Zn + H2O = ZnO + H2
Interaction with acids
In the electrochemical series of voltages of metals, zinc is before hydrogen and displaces it from non-oxidizing acids:
Zn + 2HCl = ZnCl2 + H2
Zn + H2SO4 = ZnSO4 + H2
Reacts with dilute nitric acid to form zinc nitrate and ammonium nitrate:
4Zn + 10HNO3 = 4Zn(NO3)2 + NH4NO3 + 3H2O
Reacts with concentrated sulfuric and nitric acids to form a zinc salt and acid reduction products:
Zn + 2H2SO4 = ZnSO4 + SO2 + 2H2O
Zn + 4HNO3 = Zn(NO3)2 + 2NO2 + 2H2O
Interaction with alkalis
Reacts with alkali solutions to form hydroxo complexes:
Zn + 2NaOH + 2H2O = Na2 + H2
when fused, it forms zincates:
Zn + 2KOH = K2ZnO2 + H2
Interaction with ammonia
With gaseous ammonia at 550-600°C it forms zinc nitride:
3Zn + 2NH3 = Zn3N2 + 3H2
dissolves in an aqueous solution of ammonia, forming tetraamminzinc hydroxide:
Zn + 4NH3 + 2H2O = (OH)2 + H2
Interaction with oxides and salts
Zinc displaces metals in the stress row to the right of it from solutions of salts and oxides:
Zn + CuSO4 = Cu + ZnSO4
Zinc is a metal, standing in the periodic table, at number 30 and has the designation Zn. It melts at a temperature of 419 ° C degrees, but if the boiling point is 913 ° C, it begins to turn into steam. Under normal temperature conditions, the state is fragile, and at one hundred degrees it begins to bend.
The color of zinc is blue-white. When exposed to oxygen, oxidation appears, as well as a coating of carbonate that protects the metal from further oxidation reaction. The appearance of hydroxide on zinc means that water does not act on the chemical element.
Zinc is a chemical element that has its own distinctive properties, advantages and disadvantages. It is widely used in everyday life of a person, in pharmaceuticals and metallurgy.
Features of zinc
Metal is necessary and widely used in almost all areas of human daily life.
Mining is mainly carried out in Iran, Kazakhstan, Australia, Bolivia. In Russia, the manufacturer is OAO GMK Dalpolimetall.
It is a transition metal, has an oxidation state of +2, a radioactive isotope, a half-life of 244 days.
In its pure form, the element is not mined. Contained in ores and minerals: cleophane, marmatite, wurtzite, zincite. It is necessarily present in an alloy with aluminum, copper, tin, nickel.
Chemical, physical properties and characteristics of zinc
Zinc is a metal that has a number of properties and characteristics that distinguish it from other elements of the periodic table.
The physical properties of zinc include its state. Temperature is the main factor. If at room temperature it is a brittle material, the density of zinc is 7130 kg / m 3 (˃ the density of steel), which practically does not bend, then when it rises, it easily bends and rolls in sheets in factories. If we take a higher temperature regime, the material acquires a liquid state, and if we raise the temperature by 400-450 ° C, then it will simply evaporate. This is uniqueness - to change your state. If you act with acids and alkalis, it can crumble, explode, melt.
The formula of zinc Zn is zincum. The atomic mass of zinc is 65.382 a.m.u.
Electronic formula: the nucleus of a metal atom contains 30 protons, 35 neutrons. An atom has 4 energy levels - 30 electrons. (Fig. structure of the zinc atom) 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 .
The crystal lattice of zinc is a hexagonal crystal system with tightly pressed atoms. Lattice data: A=2.66U, C=4.94.
Structure and composition of zinc
The extracted and not processed material has isotopes 64, 66, 67, electrons 2-8-18-2.
In terms of application, among all the elements of the periodic table, the metal is in 23rd place. In nature, the element appears in the form of sulfide with impurities of lead Pb, cadmium Cd, iron Fe, copper Cu, silver Ag.
Depending on how many impurities, the metal is labeled.
Zinc production
As mentioned above, there is no pure form of this element in nature. It is extracted from other rocks, such as ore - cadmium, gallium, minerals - sphalerite.
The metal is received at the factory. Each plant has its own distinctive production features, so the equipment for obtaining pure material is different. It could be like this:
- The rotors, arranged vertically, are electrolytic.
- Special kilns with a sufficiently high temperature for firing, as well as special electric kilns.
- Conveyors and baths for electrolysis.
Depending on the method of metal extraction adopted, the appropriate equipment is involved.
Obtaining Pure Zinc
As mentioned above, there is no pure species in nature. Basically, mining is done from ores, in which it comes with various elements.
To obtain pure material, a special flotation process with selectivity (selectivity) is involved. After the process, the ore breaks down into elements: zinc, lead, copper, and so on.
The pure metal extracted by this method is fired in a special furnace. There, at certain temperatures, the sulfide state of the material becomes oxide. During roasting, sulfur-containing gas is released, which is sent to produce sulfuric acid.
There are 2 ways to get metal:
- Pyrometallurgical - the process of roasting is underway, after - the resulting mass is restored using black coal and coke. The final process is settling.
- Electrolytic - the extracted mass is treated with sulfuric acid. The resulting solution is subjected to electrolysis, while the metal settles, it is melted in furnaces.
Smelting zinc in a furnace
The melting temperature of zinc in a furnace is 419-480 ° C degrees. If the temperature regime is exceeded, then the material begins to evaporate. At this temperature, an admixture of iron of 0.05% is allowed.
With an interest rate of 0.2 iron, the sheet cannot be rolled.
Various methods are used to smelt pure metal, up to the production of zinc vapors, which are sent to special tanks and there the substance falls down.
metal application
The properties of zinc allow its use in many areas. As a percentage:
- Galvanizing - up to 60%.
- Medicine - 10%.
- Various alloys containing this metal 10%.
- Tire output 10%.
- Production of paints - 10%.
And also the use of zinc is necessary for the recovery of metals such as gold, silver, platinum.
Zinc in metallurgy
The metallurgical industry uses this element of the periodic table as the main one to achieve certain goals. The smelting of pig iron and steel is the main one in the entire metallurgy of the country. But, these metals are subject to negative environmental influences. Without a certain treatment, there is a rapid oxidation of metals, which leads to their deterioration. The best protection is galvanizing.
The application of a protective film on cast iron and steel is the best remedy for corrosion. Galvanizing takes about 40% of the total production of pure material.
Galvanizing methods
Metallurgical plants are distinguished not only by their equipment, but also by the methods of production used. It depends on the pricing policy, and the location (natural resources used for the metallurgical industry). There are several galvanizing methods which are discussed below.
Hot dip galvanizing
This method consists in dipping a metal part in a liquid solution. It happens like this:
- The part or product is degreased, cleaned, washed and dried.
- Further, zinc is melted to a liquid state at temperatures up to 480 ° C.
- The prepared product is lowered into the liquid solution. At the same time, it is well wetted in solution and a coating up to 450 μm thick is formed. This is 100% protection against external factors on the product (moisture, direct sunlight, water with chemical impurities).
However, this method has a number of disadvantages:
- The zinc film on the product turns out to be an uneven layer.
- You cannot use this method for parts that meet exact GOST standards. Where every millimeter is considered a marriage.
- After hot-dip galvanizing, not every part will remain strong and wear-resistant, because brittleness appears after passing through high temperatures.
And also this method is not suitable for products coated with paints and varnishes.
Cold galvanizing
This method has 2 names: galvanic and electrolytic. The procedure for coating the product with corrosion protection is as follows:
- A metal part, the product is being prepared (degreased, cleaned).
- After that, the “staining method” is carried out - a special composition is used that has the main component - zinc.
- The part is covered with this composition by spraying.
Thanks to this method, parts with an exact tolerance, products coated with paints and varnishes are covered with protection. Increases resistance to external factors leading to corrosion.
Disadvantages of this method: thin protective layer - up to 35 microns. This results in less protection and shorter protection times.
Thermal diffusion method
This method makes a coating that is an electrode with positive polarity, while the metal of the product (steel) becomes negative polarity. An electrochemical protective layer appears.
The method is applicable only if the parts are made of carbon steel, cast iron, steel with impurities. Zinc is used in this way:
- At temperatures from 290 °C to 450 °C in a powder medium, the surface of the part is saturated with Zn. Here, the marking of steel, as well as the type of product, matter - the appropriate temperature is selected.
- The thickness of the protective layer reaches 110 microns.
- A product made of steel, cast iron is placed in a closed tank.
- A special mixture is added there.
- The last step is a special treatment of the product from the appearance of white efflorescence from salt water.
Basically, this method is used if it is required to cover parts that have a complex shape: carving, small strokes. The formation of a uniform protective layer is important because these parts are exposed to multiple external aggressive environments (constant moisture).
This method gives the highest percentage of product protection against corrosion. Galvanized coating is wear-resistant and practically indelible, which is very important for parts that rotate and disassemble from time to time.
Other applications of zinc
In addition to galvanizing, the metal is also used in other industries.
- Zinc sheets. For the production of sheet, rolling is carried out, in which ductility is important. It depends on the temperature regime. A temperature of 25 ° C gives plasticity only in one plane, which creates certain properties of the metal. The main thing here is what the sheet is made for. The higher the temperature, the thinner the metal is. Depending on this, the product is labeled C1, C2, C3. After that, various products for cars, profiles for construction and repair, for printing, and so on are created from the sheets.
- zinc alloys. For improved properties of metal products, zinc is added. These alloys are created at high temperatures in special furnaces. Most often, alloys are made from copper, aluminum. These alloys are used for the production of bearings, various bushings, which are applicable in mechanical engineering, shipbuilding and aviation.
In household use, a galvanized bucket, a trough, sheets on the roof are the norm. Zinc is used, not chrome or nickel. And it's not just that galvanizing is cheaper than coating with other materials. This is the most reliable and durable protective material than chrome or other materials used.
As a result, zinc is the most common metal widely used in metallurgy. In mechanical engineering, construction, medicine - the material is applicable not only as protection against corrosion, but also to increase strength, long service life. In private houses, galvanized sheets protect the roof from precipitation; in buildings, walls and ceilings are leveled with plasterboard sheets based on galvanized profiles.
Almost every housewife in the house has a galvanized bucket, a trough, which she uses for a long time.
