Precautions for processing and use of titanium anode plate
1. Substrate: Titanium
Titanium is a metallic element, gray, atomic number 22, relative atomic mass 47.867. Can be incinerated in nitrogen with high melting point. Dull titanium and titanium-based alloys are new structural materials, mainly used in the aerospace industry and sailing industry. Because titanium has the characteristics of high melting point, small specific gravity, high specific strength, good resistance, fatigue resistance, acid and alkali corrosion resistance, low thermal conductivity, good uneven temperature tolerance, and low stress under rapid cooling and rapid heating conditions, its commercial value is in It has been known since the 1950s and has been used in high-tech fields such as aviation and aerospace. With the continuous promotion of chemical industry, petroleum, electric power, seawater desalination, construction, daily necessities and other industries, titanium metal is increasingly valued by people and is known as modern metal, intelligent metal, and strategic metal. strategic material.
1. Physical properties, pure metal titanium is silvery white. Compared with other metal materials, the characteristics of titanium are as follows:
①The melting point is as high as 1660 degrees.
②Titanium has a close-packed hexagonal lattice at room temperature (below 885 degrees), and a body-centered cubic lattice when it is higher than 885 degrees, and the volume increases by 5.5%.
③The density of titanium is about 4.51g/cm3, which is about 60% of stainless steel, surpassing aluminum and about 60% larger than aluminum.
④Although the tensile strength of pure titanium is 350-700MPa, the general titanium alloy can reach 700-1200MPa, or even 1400MPa. As a result, the specific strength of titanium alloys (that is, the ratio of strength to density) is greater than that of any other material today.
⑤The specific heat, thermal conductivity and resistivity of titanium are at the same level as those of stainless steel, but the expansion coefficient of titanium is 50% smaller than that of steel. Titanium has poor thermal conductivity and poor electrical conductivity, similar to stainless steel.
⑥The Young's modulus of titanium is smaller than that of stainless steel, and it can bend under lower stress.
⑦Comply with stable creep characteristics in the temperature range of 200~300℃.
2. Chemical properties
①Acid with acid at room temperature, titanium is not easy to react with inorganic acid, but it can react after heating.
②Reaction with alkali Titanium reacts very slowly with ordinary alkali solutions, and does not react with dilute alkali solutions.
③ Interaction with non-metals In general, titanium is not very active, but at high temperatures, titanium can directly form very stable, hard and insoluble interstitial compounds with many non-metallic elements.
4) An important characteristic of gettering titanium is its ability to absorb gases (oxygen, nitrogen, hydrogen) violently. The role of titanium and oxygen and nitrogen is irreversible, so titanium is an excellent getter. Absorbed in titanium can be discharged from the metal when heated to 800-900 degrees in a vacuum.
3. The ratio of strength to density of titanium is higher than that of iron and aluminum. It is 1 times stronger than pure iron and 5 times stronger than pure aluminum.
2. Titanium electrode The full name of titanium anode is titanium-based metal oxide-coated titanium anode (MMO). Also called DSA anode (standard shape stable anode). It uses titanium as the substrate, and brushes the noble metal coating on the titanium substrate, so that it has outstanding electrocatalytic activity and electrical conductivity.
Compared with original graphite anode and lead anode, titanium electrode has the following advantages:
1. The electrode size is relatively stable, and the distance between the electrodes will not change during the process of electrolysis, ensuring that the electrolysis operation is carried out under the condition of stable cell voltage;
2. High catalytic activity and low operating voltage;
3. The operating voltage is low, so the power consumption is small, and the DC power consumption can be reduced by 10%---20%;
4. The working life of titanium anode is long, and the metal anode is resistant to chlorine and alkali corrosion in the production industry.
5. It can overcome the dissolution problem of graphite anode and lead anode, and prevent the pollution of electrolyte and cathode products, thus greatly improving the purity of metal products;
6. It can improve the current density and increase the electrolysis power;
7. The oxides of noble metals iridium and ruthenium have oxidation resistance, so titanium electrodes have strong corrosion resistance;
8. It can prevent the short-circuit problem after the lead anode is deformed, and then the power of the current can be increased;
9. Titanium electrodes are light in weight, which can reduce labor intensity compared with graphite anodes and lead anodes;
10. The shape and manufacture of the titanium matrix are relatively simple and can be highly precise;
11. Under the premise of no damage, the substrate can be used repeatedly;
Titanium anode classification:
1. According to the separation of gas from the anode in the electrochemical reaction, the separated anode is called chlorine evolution anode, such as ruthenium-based coated titanium electrode: the separated oxidized anode is called oxygen evolution anode, such as iridium-based coated titanium electrode and platinum electrode Titanium mesh/plate. Chlorine-evolution anode (ruthenium-coated titanium electrode): The chloride ion content in the electrolyte is high, and it is generally used in the environment and the electrolysis of seawater and salt water. The corresponding products of our company are ruthenium iridium titanium anode and ruthenium iridium tin titanium anode.
2. Oxygen evolution anode (iridium-coated titanium electrode): The electrolyte is generally a sulfuric acid environment. The corresponding products of our company are iridium tantalum anode, iridium tantalum tin titanium anode, high iridium titanium anode.
3. Platinum-coated anode: titanium is the base material. The surface is coated with platinum, the thickness of the coating is generally 0.5-5μm, and the mesh size of the platinum titanium mesh is generally 12.5×4.5mm or 6×3.5mm.
3. Introduction to the production process
1. Select the TA1 grade titanium substrate, and determine that the surface of the substrate is smooth and flat, without scratches, peeling, cracking, delamination and other defects.
2. Machining the selected titanium substrate to meet the specifications required by customers.
3. The titanium substrate is annealed and leveled at a temperature of 600 °C.
4. During the annealing and leveling treatment, the surface of the titanium substrate will form a fine titanium oxide layer, which is polished mechanically to make the surface of the titanium metallic luster.
5. Use 10% concentration of oxalic acid to pickle and corrode the titanium substrate, and perform it in a slightly boiling state for 10 hours to etch the surface oxide layer into the surface.
6. Carry out reasonable qualitative and quantitative equipment for precious metal solutions according to the anode environment used by customers.
7. Detect that the acid-washed titanium substrate is qualified, that is, the surface layer is a gray and uniform pockmarked surface structure, and then it is manually coated, sintered at a suitable temperature, and naturally cooled after sintering, and the second coating is performed when it is cooled to room temperature. Shoe, and so on, until more than 18 to 22 times the equipment solution is applied.
8. After the sintering of the above processed parts is completed, the life test is carried out with the furnace test piece, and the test is qualified and packaged for delivery.
4. The primary scope of application
1. Electrolysis production of chlorate industry in chlor-alkali industry
The chemical industry that extracts and mixes caustic soda by means of electrolysis of salt water is called the chlor-alkali industry, which is the largest part of the modern electrochemical industry and occupies an important position in the national economy. In addition to the above, it can also produce downstream products such as hydrogen chloride, secondary, chlorinated stone, polyvinyl chloride (referred to as PVC Polyvinyl chloride polymer = PVC molecular structure), etc. In the production of chlor-alkali, pure saturated salt water is used as the electrolytic solution, titanium electrode is used as the anode, and iron mesh with asbestos wool is used as the cathode. The use of titanium anodes has greatly promoted the development of the chlor-alkali industry and is an epoch-making contribution to the field of electrochemistry. The electrode has high catalytic activity for chlorine evolution, and has excellent electrocatalytic activity, mechanical stability and chemical stability for chlorine evolution. In today's chlor-alkali industry, it is an irreplaceable electrode material with a service life of more than five years.
2. Water for electrolysis
Functional water is defined as water that has been artificially treated to obtain various useful functions. Electrolyzed water is popular as a sterilization treatment technology with good sterilization effect, strong practicability and no secondary pollution. It is widely used in electrolyzed water machines to generate functional water through titanium electrode electrolysis of drinking water or trace amount of salt water.
①Using electrolysis to generate hypochlorite, new ecological oxygen, hydroxyl radicals and other strong oxidizing substances to kill microorganisms.
②Using electrolytic electrodes to directly act on microorganisms to make them die.
③Alkaline ionized water can directly treat a variety of diseases, effectively improve the function of the human body to produce new products, eliminate harmful free radicals of acidic metabolites, and enhance physical fitness to prevent and improve disease resistance.
④Acid ionized water has the functions of inhibiting the growth of bacteria, sterilizing and astringent, which is the same as the astringent water for beauty.
3. Secondary generator and generator electrode production.
The temperature of the secondary electrolysis should be maintained below 40°C. If the temperature is too high, NaClO will decompose, reducing the solubility of Cl2, which is not conducive to the generation of NaClO. The solution is alkaline, and the addition of anode O2 will reduce the current power of chlorine evolution. The electrode spacing is 3~10mm, and the reduction of the electrode spacing can reduce the tank pressure and power consumption. The current density is 13~20A/dm2 when using the coated titanium electrode. The power consumption of the secondary generator is generally about 3.7~7kW·h/kg.
The generator uses a partition electrolytic cell to electrolyze the sodium chloride solution to generate a mixed gas, which is dissolved in water to form a sterilization and disinfection liquid. The second molecular formula is ClO2, which is easily soluble in water, decomposes in water, and easily reacts with water. The solubility in water is 5-8 times that of chlorine. Dissolved in alkaline solution to generate chlorite and chlorate.
4. Cathode maintenance
Because in the marine, hull, bridge and other steel application environments, due to the corrosion effect of impurities in the steel and micro-battery, and the chaotic natural environment, although the corrosion-resistant alloy steel is selected and the material thickness is added to coat the excellent corrosion-resistant paint, the The corrosion of these structures is still very serious, which greatly threatens safe production, and cathodic protection is a convenient and important method for effective maintenance of permanent steel structures in the ocean.
①Using an applied current to make the entire surface of the metal structure to be protected become a cathode, which is called impressed current cathode protection.
②Connecting a metal or alloy with a more negative potential to the metal equipment that needs maintenance is called dedicated anode maintenance.
Apply to the following areas:
1) In fresh water and sea water, prevent corrosion of ships, docks, channels, gates and cooling equipment.
2) In alkali and salt solutions, prevent the corrosion of storage tanks, transpiration tanks, alkali boiling pots, etc.
3) Prevent corrosion of pipelines and cables in soil and sea mud.
5. Gold-plated, steel galvanized and tin-plated
Titanium electrode has excellent electrical conductivity and corrosion resistance, and its service life is much higher than that of lead anode. It can operate stably for more than 4,000 hours and has low cost. It will be an inevitable trend for the development of electro-galvanizing and tin production at home and abroad. Titanium electrodes are currently used in Japan, the United States, Germany, and China, which not only greatly saves electroplating energy consumption, but also creates conditions for the production of thick galvanized and tin steel plates because it can increase the current density of electroplating.
6. Non-ferrous metal extraction
Electrolytic metallurgy occupies a large proportion in the hydrometallurgical industry. The non-ferrous metals produced by electrolytic metallurgy include Zn, Cd, Cu, Mn, Co, Ni, Cr, etc.
The advantage of electrolytic metallurgy is that it has high selectivity, can obtain high-purity metals, and can recover useful metals, so it can process low-grade minerals and polymetallic ores with complex components, which is conducive to the comprehensive utilization of resources. In addition, the pollution to the environment is less, and the production is easier to serialize and automate. Coated titanium electrodes have been widely used in the field of electrolytic extraction of metals in recent years, and it has become the second industrial field that plans to use titanium electrodes.
7. Electrolytic copper foil
With the development of science and technology, the degree of automation is increasing day by day, which has promoted the rapid development of the electronics industry. The use of large-scale integrated circuits has increased the demand for copper foil in the electronics and exterior industries, and the quality requirements of copper foil are also getting higher and higher. According to the thickness, it can be divided into 105?m, 70?m, 35?m, 18?m, 12?m, 9?m and 5?m, among which copper foil below 12?m is generally called ultra-thin copper foil. The electrolytic copper foil uses a metal roller partially immersed in a copper sulfate solution that rotates continuously as the cathode, and the foil is continuously electrolyzed. The international copper foil production is mainly controlled by Japan, and there are about fifteen domestic manufacturers with a production capacity of about 35,000 tons.
8. Sewage treatment
With the rapid development of industry and agriculture and population growth, the amount of sewage discharged by humans has increased sharply, resulting in many waters being polluted to varying degrees. Electrochemical treatment of sewage is divided into direct electrolysis and direct electrolysis.
①Direct electrolysis means that pollutants are directly oxidized or restored on the electrode to be removed from the wastewater. Direct electrolysis can be divided into cathodic process and anodic process. The anode process refers to the oxidation of pollutants on the anode surface and the conversion into less toxic substances or easily biodegradable substances, and even the inorganicization of organic matter, and then achieves the purpose of reducing pollution. The cathode process refers to the recovery of pollutants on the cathode surface. It is mainly used for the restoration and dehalogenation of halogenated hydrocarbons and the recovery of heavy metals.
②Direct electrolysis refers to the use of electrochemically generated oxidation-reduction substances as reactants or catalysts to convert pollutants into less toxic substances. Direct electrolysis can be divided into reversible processes and irreversible processes. The reversible process refers to the electrochemical regeneration and recycling of the redox substances in the electrolysis process; the irreversible process refers to the oxidation of organic substances by the use of substances that cannot be reversed electrochemically. Used in printing and dyeing wastewater treatment, waste leachate treatment, drying sewage treatment, wastewater treatment, pharmaceutical wastewater treatment, hospital sewage treatment, organic wastewater treatment.
9. Etching solution regeneration and copper recovery
Etching is an important process in the production of printed circuit boards. Following etching, the waste etching solution contains a lot of copper ions or other metal ions, which can be recycled through electrolysis. After this recovery process, manufacturers not only increase economic benefits by recovering metals such as copper, but also have long-term social benefits by qualifying emissions and recycling resources. The waste liquid includes: acid etching waste liquid, alkaline etching waste liquid, low copper-containing waste liquid, waste fixing liquid, waste frame material, nickel-containing waste liquid, waste liquid containing gold and palladium, waste tin stripping water.
5. Precautions for the use of electrodes
1. The titanium electrode has a black surface after oxidation and sintering. The uncoated surface is blue and has no electrode function. The black side corresponds to the cathode application.
2. Once the titanium electrode substrate is pickled, it is necessary to carry out all the production, processing and application procedures in the future with strict care. Wear clean gloves to block the ends or edges of the anode during transportation. It is best to touch the uncoated part. The coating surface is prohibited from being scratched by any foreign objects.
Note: The titanium substrate itself is not conductive, and its outer layer is coated with a noble metal oxide coating that has electrocatalytic activity, conductivity and oxidation resistance, but its thickness is only about 30 microns. During the process, the electrode will first corrode from the damage, which will affect the quality and function of the entire electrode.
3. The electrolyte maintains stability, especially can not contain ions and fluoride ions, these impurities will seriously corrode the titanium matrix;
4. Add filter equipment before the electrolyte enters the electrolytic cell, and cannot contain metal particles with a diameter greater than 0.1mm to prevent the anode and cathode short circuit due to excessive aggregation.
5. When recovering copper, nickel, gold, silver, cobalt and other metals by electrolysis, the cathode attachment should not be too thick to prevent the short-circuit breakdown of the cathode and anode due to the formation of too small electrode distance or the formation of sharp metal.
6. The distance between cathode and anode can be set according to actual production, generally 5-25mm. On the whole, the voltage drop will be added to the pole distance, but it should not be too small, otherwise the cathode scale on the cathode surface will easily form a short circuit of the plate;
7. Prevent reverse pole use. Once the precious metal oxide coating is used as a cathode, the surface will undergo a recovery reaction, and it is easy to transform into a metal element, which cannot be combined with the titanium base.
