Chemical Properties of Titanium and Its Reaction with Different Elements
Key words: chemical properties of titanium, chemical reaction of titanium alloy, TiF4 formation from titanium, Covalent bond, ionic bond compound, intermetallic compound, finite solid solution, infinite solid solution
Titanium reacts with many elements and compounds at higher temperatures. Various elements can be divided into four categories according to their different reactions with titanium:
The first category:: A halogen and an oxygen group form a covalent bond and an ion bond compound with titanium;
The second category: Transition elements, hydrogen, antimony, boron, carbon and nitrogen elements and titanium form intermetallic compounds and finite solid solutions;
The third category: Zirconium, hafnium, vanadium, chromium, antimony and titanium form an infinite solid solution;
The fourth category: Inert gases, alkali metals, alkaline earth metals, rare earth elements (except for cerium), cerium, lanthanum, etc. do not react with or substantially do not react with titanium.
Reaction of titanium with compounds:
HF and fluoride
The hydrogen fluoride gas reacts with titanium to form TiF4 when heated, and the reaction formula is (1) Ti+4HF=TiF4+2H2+135.0 kcal; The non-aqueous hydrogen fluoride liquid forms a dense titanium tetrafluoride film on the titanium surface to prevent HF from immersing inside the titanium. Hydrofluoric acid is the strongest flux of titanium. Even hydrofluoric acid with a concentration of 1% can react violently with titanium, see formula (2) 2Ti + 6HF = 2TiF4 + 3H2 ; Anhydrous fluorides and their aqueous solutions do not react with titanium at low temperatures, but only fluorides melted at high temperatures react significantly with titanium.
HCl and chloride
Hydrogen chloride gas can corrode metal titanium, and dried hydrogen chloride reacts with titanium to form TiCl4 at >300 °C, see Ti+4HCl=TiCl4+2H2+94.75 kcal;
The concentration of hydrochloric acid < 5% does not react with titanium at room temperature, and 20% of hydrochloric acid reacts with titanium to produce purple TiCl3 at room temperature. See formula 2Ti+6HCl=TiCl3+3H2.
When the temperature is high, even dilute hydrochloric acid corrodes titanium. Various anhydrous chlorides such as magnesium, manganese, iron, nickel, copper, zinc, mercury, tin, calcium, sodium, antimony and NH4 ions and their aqueous solutions do not react with titanium. Titanium has good stability in these chlorides.
Sulfuric acid and hydrogen sulfide
Titanium reacts with <5% dilute sulfuric acid to form a protective oxide film on the titanium surface to protect the titanium from corrosion by dilute acid. However, >5% sulfuric acid has a significant reaction with titanium. At room temperature, about 40% of sulfuric acid has the fastest corrosion rate to titanium. When the concentration is greater than 40%, the corrosion rate becomes slower when it reaches 60%, and 80% reaches the fastest. The heated dilute acid or 50% concentrated sulfuric acid can react with titanium to form titanium sulfate, see Ti+H2SO4=TiSO4+H2, 2Ti+3H2SO4=Ti2(SO4)3+H2. The heated concentrated sulfuric acid can be reduced by titanium to form SO2, see formula 2Ti+6H2SO4=Ti2(SO4)3+3SO2+6H2O+202 kcal. At room temperature, titanium reacts with hydrogen sulfide to form a protective film on the surface to prevent further reaction of hydrogen sulfide with titanium. However, at high temperature, hydrogen is precipitated from the reaction between hydrogen sulfide and titanium. See Ti+H2S=TiS+H2+70 kcal. Powder titanium reacts with hydrogen sulfide to form titanium sulfide at 600 ℃. The main reaction products are TiS at 900℃ and Ti2S3 at 1200 C.
Nitric acid and aqua regia
The dense surface of the titanium has good stability to nitric acid, because nitric acid can quickly form a strong oxide film on the titanium surface. However, rough surface, especially sponge titanium or powder titanium, can react with hot dilute nitric acid. See formula 3Ti + 4HNO 3 + 4H 2O = 3H 4Ti 4 + 4NO, 3Ti + 4HNO 3 + H 2O = 3H 2O + 4NO; Concentrated nitric acid above 70 °C can also react with titanium, see Ti+8HNO3=Ti(NO3)4+4NO2+4H2O; At room temperature, titanium does not react with aqua regia. At high temperatures, titanium reacts with aqua regia to form TiCl2.
In summary, the nature of titanium has an extremely close relationship with temperature and its presence and purity. Dense titanium metal is quite stable in nature, but powdered titanium can cause spontaneous combustion in air. The presence of impurities in titanium significantly affects the physical, chemical, mechanical and corrosion resistance properties of titanium. In particular, some interstitial impurities, which can distort the titanium lattice and affect various properties of titanium. At normal temperature, titanium has little chemical activity and can react with a few substances such as hydrofluoric acid. However, the activity of titanium increases rapidly as the temperature increases, especially at high temperatures, which can react violently with many substances. The smelting process of titanium is generally carried out at a high temperature of 800 ° C or higher, and therefore must be operated under vacuum or under an inert atmosphere.
Note: 1. Corrosion resistance grade is divided into three levels:
Excellent - corrosion resistance, corrosion rate below 0.127mm / a.
Good - moderate corrosion resistance, corrosion rate between 0.127-1.27mm / a.
Poor - not resistant to corrosion, corrosion rate is above 1.27mm / a.
2. Pure titanium has high corrosion resistance in most media, especially in neutral, oxidizing media and seawater. Titanium has higher corrosion resistance in seawater than aluminum alloys, stainless steels and nickel alloys. In the atmosphere of industrial, agricultural and marine environments, the surface does not change color for years. Hydrofluoric acid, sulfuric acid, hydrochloric acid, orthophosphoric acid and some hot concentrated organic acids corrode titanium significantly (see table above). Among them, hydrofluoric acid has a high corrosive effect on titanium regardless of its concentration and temperature. Titanium has high stability to various concentrations of nitric acid and chromic acid, and has high corrosion resistance in alkali solutions and most organic acid and inorganic salt solutions.
3. Titanium does not suffer from local corrosion and intergranular corrosion, and the corrosion is uniform.
4. The corrosion resistance of titanium alloys is similar to that of industrial pure titanium, which is why titanium alloys are widely used in the chemical and shipbuilding industries.
Titanium reacts with many elements and compounds at higher temperatures. Various elements can be divided into four categories according to their different reactions with titanium:
The first category:: A halogen and an oxygen group form a covalent bond and an ion bond compound with titanium;
The second category: Transition elements, hydrogen, antimony, boron, carbon and nitrogen elements and titanium form intermetallic compounds and finite solid solutions;
The third category: Zirconium, hafnium, vanadium, chromium, antimony and titanium form an infinite solid solution;
The fourth category: Inert gases, alkali metals, alkaline earth metals, rare earth elements (except for cerium), cerium, lanthanum, etc. do not react with or substantially do not react with titanium.
Reaction of titanium with compounds:
HF and fluoride
The hydrogen fluoride gas reacts with titanium to form TiF4 when heated, and the reaction formula is (1) Ti+4HF=TiF4+2H2+135.0 kcal; The non-aqueous hydrogen fluoride liquid forms a dense titanium tetrafluoride film on the titanium surface to prevent HF from immersing inside the titanium. Hydrofluoric acid is the strongest flux of titanium. Even hydrofluoric acid with a concentration of 1% can react violently with titanium, see formula (2) 2Ti + 6HF = 2TiF4 + 3H2 ; Anhydrous fluorides and their aqueous solutions do not react with titanium at low temperatures, but only fluorides melted at high temperatures react significantly with titanium.
HCl and chloride
Hydrogen chloride gas can corrode metal titanium, and dried hydrogen chloride reacts with titanium to form TiCl4 at >300 °C, see Ti+4HCl=TiCl4+2H2+94.75 kcal;
The concentration of hydrochloric acid < 5% does not react with titanium at room temperature, and 20% of hydrochloric acid reacts with titanium to produce purple TiCl3 at room temperature. See formula 2Ti+6HCl=TiCl3+3H2.
When the temperature is high, even dilute hydrochloric acid corrodes titanium. Various anhydrous chlorides such as magnesium, manganese, iron, nickel, copper, zinc, mercury, tin, calcium, sodium, antimony and NH4 ions and their aqueous solutions do not react with titanium. Titanium has good stability in these chlorides.
Sulfuric acid and hydrogen sulfide
Titanium reacts with <5% dilute sulfuric acid to form a protective oxide film on the titanium surface to protect the titanium from corrosion by dilute acid. However, >5% sulfuric acid has a significant reaction with titanium. At room temperature, about 40% of sulfuric acid has the fastest corrosion rate to titanium. When the concentration is greater than 40%, the corrosion rate becomes slower when it reaches 60%, and 80% reaches the fastest. The heated dilute acid or 50% concentrated sulfuric acid can react with titanium to form titanium sulfate, see Ti+H2SO4=TiSO4+H2, 2Ti+3H2SO4=Ti2(SO4)3+H2. The heated concentrated sulfuric acid can be reduced by titanium to form SO2, see formula 2Ti+6H2SO4=Ti2(SO4)3+3SO2+6H2O+202 kcal. At room temperature, titanium reacts with hydrogen sulfide to form a protective film on the surface to prevent further reaction of hydrogen sulfide with titanium. However, at high temperature, hydrogen is precipitated from the reaction between hydrogen sulfide and titanium. See Ti+H2S=TiS+H2+70 kcal. Powder titanium reacts with hydrogen sulfide to form titanium sulfide at 600 ℃. The main reaction products are TiS at 900℃ and Ti2S3 at 1200 C.
Nitric acid and aqua regia
The dense surface of the titanium has good stability to nitric acid, because nitric acid can quickly form a strong oxide film on the titanium surface. However, rough surface, especially sponge titanium or powder titanium, can react with hot dilute nitric acid. See formula 3Ti + 4HNO 3 + 4H 2O = 3H 4Ti 4 + 4NO, 3Ti + 4HNO 3 + H 2O = 3H 2O + 4NO; Concentrated nitric acid above 70 °C can also react with titanium, see Ti+8HNO3=Ti(NO3)4+4NO2+4H2O; At room temperature, titanium does not react with aqua regia. At high temperatures, titanium reacts with aqua regia to form TiCl2.
In summary, the nature of titanium has an extremely close relationship with temperature and its presence and purity. Dense titanium metal is quite stable in nature, but powdered titanium can cause spontaneous combustion in air. The presence of impurities in titanium significantly affects the physical, chemical, mechanical and corrosion resistance properties of titanium. In particular, some interstitial impurities, which can distort the titanium lattice and affect various properties of titanium. At normal temperature, titanium has little chemical activity and can react with a few substances such as hydrofluoric acid. However, the activity of titanium increases rapidly as the temperature increases, especially at high temperatures, which can react violently with many substances. The smelting process of titanium is generally carried out at a high temperature of 800 ° C or higher, and therefore must be operated under vacuum or under an inert atmosphere.
Titanium corrosion data
|
Medium
|
Concentration (mass fraction) (%) | Temperature / °C | Corrosion speed / mm / a (years) | Corrosion rating | |
| Inorganic acid |
hydrochloric acid |
1 | Room temperature / boiling | 0.000/0.345 | Excellent / good |
| 5 | Room temperature / boiling | 0.000/6.530 | Good/poor | ||
| 10 | Room temperature / boiling | 0.175/40.87 | Good/poor | ||
| 20 | Room temperature / - | 1.340/— | poor /- | ||
| 35 | Room temperature / - | 6.660/— | poor /- | ||
| sulfuric acid | 5 | Room temperature / boiling | 0.000/13.01 | Good/poor | |
| 10 | Room temperature / - | 0.230/— | Good / - | ||
| 60 | Room temperature / - | 0.277/— | Good/poor | ||
| 80 | Room temperature / - | 32.660/— | poor /- | ||
| 95 | Room temperature / - | 1.400/— | poor /- | ||
| Nitric acid | 37 | Room temperature / boiling | 0.000/<0.127 | Excellent / good | |
| 64 | Room temperature / boiling | 0.000/<0.127 | Excellent / good | ||
| 95 | Room temperature / - | 0.0025/— | Good / - | ||
| Phosphate | 10 | Room temperature / boiling | 0.000/6.400 | Good/poor | |
| 30 | Room temperature / boiling | 0.000/17.600 | Good/poor | ||
| 50 | Room temperature / - | 0.097/— | Good / - | ||
| Chromic acid | 20 | Room temperature / boiling | <0.127/<0.127 | Good/poor | |
| Nitric acid + hydrochloric acid | 1:3 | Room temperature / boiling | 0.0040/0.127 | Good/poor | |
| 3:1 | Room temperature / - | <0.127/— | Good / - | ||
| Nitric acid + sulfuric acid | 7:3 | Room temperature / - | <0.127/— | Good / - | |
| 4:6 | Room temperature / - | <0.127/— | Good / - | ||
| Organic acid | acetic acid | 100 | Room temperature / boiling | 0.000/0.000 | Good/poor |
| formic acid | 50 | Room temperature / - | 0.000/— | Good / - | |
| oxalic acid | 5 | Room temperature / boiling | 0.127/29.390 | Good/poor | |
| 10 | Room temperature / - | 0.008/— | Good / - | ||
| Lactic acid | 10 | Room temperature / boiling | 0.000/0.033 | Excellent / good | |
| 25 | - /boiling | —/0.028 | - /good | ||
| Formic acid | 10 | - /boiling | —/1.270 | - /good | |
| 25 | —/100 | —/2.440 | -/ poor | ||
| 50 | —/100 | —/7.620 | -/ poor | ||
| Danlic acid | 25 | Room temperature / boiling | <0.127/<0.127 | Excellent / good | |
| Citric acid | 50 | Room temperature / boiling | <0.127/<0.127 | Excellent / good | |
| Stearic acid | 100 | Room temperature / boiling | <0.127/<0.127 | Excellent / good | |
| Alkaline solution | Sodium hydroxide | 10 | - /boiling | —/0.020 | - /good |
| 20 | Room temperature / boiling | <0.127/<0.127 | Excellent / good | ||
| 50 | Room temperature / boiling | <0.0025/0.0508 | Excellent / good | ||
| 73 | - /boiling | —/0.127 | - /good | ||
| Potassium hydroxide | 10 | - /boiling | —/<0.127 | - /good | |
| 25 | - /boiling | —/0.305 | - /good | ||
| 50 | 30/boiling | 0.000/2.743 | Good/poor | ||
| Ammonium hydroxide | 28 | Room temperature / - | 0.0025/— | good / - | |
| Sodium carbonate | 20 | Room temperature / boiling | <0.127/<0.127 | Excellent / good | |
| Armonia | 20 | Room temperature / - | 0.0708/— | good / - | |
| Inorganic salt solution | Ferric chloride | 40 | Room temperature/95 | 0.000/0.002 | Excellent / good |
| Ferrous chloride | 30 | Room temperature / boiling | 0.000/<0.127 | Excellent / good | |
| Lead chloride | 10 | <0.127/<0.127 | |||
| Cuprous chloride | 50 | <0.127/<0.127 | |||
| Ammonium chloride | 10 | <0.127/<0.000 | |||
| Calcium chloride | 10 | <0.127/<0.000 | |||
| Aluminum chloride | 25 | <0.127/<0.127 | |||
| Magnesium chloride | 10 | <0.127/<0.127 | |||
| Nickel chloride | 5-10 | <0.127/<0.127 | |||
| Barium chloride | 20 | <0.127/<0.127 | |||
| Copper sulfate | 20 | <0.127/<0.127 | |||
| Ammonium sulfate | 20℃ saturation | <0.127/<0.127 | |||
| Sodium sulfate | 50 | <0.127/<0.127 | |||
| Lead sulfate | 20℃ saturation | <0.127/<0.127 | |||
| Cuprous sulfate | 10 | <0.127/<0.127 | |||
| 30 | <0.127/<0.127 | ||||
| Silver nitrate | 11 | Room temperature / - | <0.127/— | good / - | |
| Organic compound | Benzene (containing trace amounts of HCl, NaCl) | Vapor and liquid | 80 | 0.005 | Excellent |
| Carbon tetrachloride | Ibid. | boiling | 0.005 | ||
| Tetrachloroethylene (stable) | 100% Vapor and liquid | 0.0005 | |||
| Tetrachloroethylene (H2O) | 0.0005 | ||||
| Trichloromethane | 0.003 | ||||
| Trichloromethane (H2O) | 0.127 | Excellent | |||
| Trichloroethylene | 99% Vapor and liquid | 0.00254 | Excellent | ||
| Trichloroethylene (stable) | 99 | 0.00254 | |||
| formaldehyde | 37 | 0.127 | Excellent | ||
| Formaldehyde (including 2.5% H2SO4) | 50 | 0.305 | Excellent | ||
Note: 1. Corrosion resistance grade is divided into three levels:
Excellent - corrosion resistance, corrosion rate below 0.127mm / a.
Good - moderate corrosion resistance, corrosion rate between 0.127-1.27mm / a.
Poor - not resistant to corrosion, corrosion rate is above 1.27mm / a.
2. Pure titanium has high corrosion resistance in most media, especially in neutral, oxidizing media and seawater. Titanium has higher corrosion resistance in seawater than aluminum alloys, stainless steels and nickel alloys. In the atmosphere of industrial, agricultural and marine environments, the surface does not change color for years. Hydrofluoric acid, sulfuric acid, hydrochloric acid, orthophosphoric acid and some hot concentrated organic acids corrode titanium significantly (see table above). Among them, hydrofluoric acid has a high corrosive effect on titanium regardless of its concentration and temperature. Titanium has high stability to various concentrations of nitric acid and chromic acid, and has high corrosion resistance in alkali solutions and most organic acid and inorganic salt solutions.
3. Titanium does not suffer from local corrosion and intergranular corrosion, and the corrosion is uniform.
4. The corrosion resistance of titanium alloys is similar to that of industrial pure titanium, which is why titanium alloys are widely used in the chemical and shipbuilding industries.
