Basic knowledge and application of titanium anode
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Basic knowledge and application of titanium anode

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Detailed explanation of titanium anode

What is a titanium anode? The full name of titanium anode is titanium-based metal oxide coated titanium anode [MMO]. Also called DSA anode. [Dimensional and shape-stable anode]. It uses titanium as the substrate, and brushes the noble metal coating on the titanium substrate, so that it has good electrocatalytic activity and electrical conductivity.

Classification of titanium anodes: according to the gas evolution of the anode in the electrochemical reaction, the chlorine evolution anode is called chlorine evolution anode, such as ruthenium coating titanium electrode: the oxygen evolution anode is called oxygen evolution anode, such as iridium coating titanium electrode and platinum electrode Titanium mesh/plate.

Chlorine anode [ruthenium coating titanium electrode]: high chloride ion content in the electrolyte: generally in the environment of hydrochloric acid, electrolysis of seawater, and electrolysis of salt water. Such as ruthenium iridium titanium anode, ruthenium iridium tin titanium anode.

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 anode and high iridium anode.

Platinum-plated anode [platinum titanium mesh/platinum titanium plate]: titanium is the base material. The surface is plated with precious metal platinum, and the thickness of the coating is generally 1-5um [micron]. The mesh size of platinum titanium mesh is generally 12.7*4.5mm or 6*3.5mm.

The advantages of titanium anode

At present, domestic titanium anodes are mainly brushed. Such electrodes have a very wide range of applications. Titanium anodes are also known as DSA anodes due to their lightweight and flexible manufacturing process. Compared with similar anodes, titanium anodes have the following advantages;best platinized electrode - qinhuangwater

1. The anode size is stable, and the distance between the electrodes does not change during the electrolysis process, which can ensure the electrolysis

The operation was carried out with the cell voltage stable.

2. Low working voltage, low power consumption, DC power consumption can be reduced by 10-20%.

3. Titanium anode has long working life and strong corrosion resistance.

4. It can overcome the dissolution problem of graphite anode and lead anode, prevent the contamination of electrolyte and cathode products, and thus improve the purity of metal products.

5. High current density, small overpotential, high catalytic activity of electrode, can effectively catch high production


6. It can prevent the short circuit problem after the deformation of the lead anode and improve the current efficiency.

7. The shape is easy to make and high precision is possible.

8. The titanium base is reusable.

9. Low overpotential characteristics, easy removal of bubbles on the surface between electrodes and electrodes, which can effectively reduce the voltage of the electrolytic cell.

Electrowinning metal extraction is a method of recovering the metal ions to be extracted in the leached and purified electrolyte at the cathode to obtain pure metal. Active layer composition.

In electrolytic metallurgy, it can replace the conventional lead alloy anode. Under the same conditions, it can reduce the voltage and save power consumption. For example: the electrolytic production of zinc has always used lead alloy anodes containing small amounts of silver, antimony or calcium. The following problems often occur: the lead alloy electrode is unstable in size; the oxygen evolution potential is too high (about 800mV); corrosion occurs when the anode is polarized; lead ions are dissolved in the electrolyte and deposited on the cathode, polluting metal zinc and affecting product quality . Titanium anodes for electrowinning metals can overcome the disadvantages of lead alloy anodes, and are suitable for high current density operation and narrow electrode spacing conditions; not only for sulfate systems, but also for chloride systems, as well as sulfate, chloride mixed system.

What is the role of the metal oxide coating on the titanium anode?

By covering with different coatings, the electrical conductivity and electrocatalytic activity are enhanced, the electrolytic reaction process is promoted, and the service life of the anode in different use environments is prolonged, so as to achieve the expected use effect.

Thickness issues of metal oxide coatings on titanium anodes

The electrochemical catalytic reaction is mainly the precious metal in the coating. Only the content of the precious metal meets the requirements to ensure the normal operation of the anode product. The thickness is only an appearance, which is mainly determined by the number of brushing times and the concentration of the solvent, and the content of the precious metal. There is no direct connection, and the coating that is too thick is more likely to fall off.

The difference between MMO titanium plate and platinized titanium anode

1. Technical characteristics: excellent antibacterial corrosion performance; long electrode service life; high current density and high current efficiency. Operating current density: 10000A/M2 belongs to the oxygen evolution anode with industrial pure titanium as the base layer.

2. High catalytic activity: Compared with the mercurous sulfate] electrode, the oxygen evolution zone of the anode is more prone to oxygen evolution. Therefore, during electrolysis, the cell voltage is also relatively low, which saves electricity. This phenomenon has been clearly expressed in the alkaline copper plated wall after copper foil treatment.

3. No pollution. MMO The oxide is a fairly stable oxide and the anode coating is a ceramic oxide of the precious metal iridium. It is almost insoluble in any acid and alkali, and the oxide coating is about 20-40μm. The overall coating oxide content is small. Therefore, the MMO anode will not pollute the plating solution, which is basically the same as the platinum-plated electrode.

4. High cost performance: The price of MMO anode is about 80% of that of platinum-plated electrode. MMO electrode has better electrochemical stability in alkaline copper electroplating electrolyte, and has maintained the same service life of platinum-plated electrode (coating thickness 3.5mm). . At the same time, it has excellent electrolytic activity and durability. ]

5. Chloride in the sulfuric acid electrolyte exists in this current environment. The use of dimensionally stable anodes prevents this phenomenon and allows insoluble anode technology to successfully achieve performance advantages in this application.

6. Anode maintenance is minimal. There is no need to stop production to clean and replenish anodes, replace anode bags, and recoat anodes (increased productivity, reduced labor rates).

7. The life of the insoluble anode depends on the type, working current density and contact with various electroplating chemicals; since copper ions are easily concentrated in the edge part of the hole (high current density area) and rapidly accumulate, and the central part of the hole (i.e. low current Density region] the packing rate is relatively much slower. This results in a very non-uniform copper packing distribution: behavior called "dog-bone" operation at moderate current densities results in dog-bone, at lower current densities barrel cracking, and at higher current densities Burning occurs. It is undoubtedly a heavy impact for electroplated circuit boards. The use of platinum-titanium insoluble anodes is used in sulfuric acid electrolytes, and reverse pulse plating anodes are also born. Chloride is present in this galvanic environment and can cause the platinum layer to peel off after a period of time.

Consideration basis for designing titanium electrode types

1. Requirements for anodes in the installation of titanium electrode electrolyzers;

2. Titanium electrode process conditions, such as electrolyte (liquid) composition, temperature, current density, service life, etc.;

3. Mechanical load of titanium electrodes;

4. Conductivity of the titanium electrode base material.

6. What are the main factors affecting the service life of anodes:

1. Current density: Current density is inversely proportional to anode life. The greater the current, the shorter the anode life.

2. Titanium substrate: The substrate of the anode is generally pure titanium, and it is required to be above the material of TA1. If the purity of the substrate used is not enough, the corrosion resistance will be greatly reduced, which will have a great impact on the service life of the anode.

3. Electrolyte: It is forbidden to contain fluoride ion, cyanide ion and sulfur ion in the electrolyte, if there is, it will have a great influence on the life of the anode.

4. Plunge: .

5. Frequent power outages: In the absence of current flow, the coating will be greatly damaged by prolonged immersion in the solution.

6. Man-made damage: The surface of the anode should not be damaged. If part of the coating is damaged, even a small scratch will cause the anode to be rapidly corroded/passivated and eventually lead to failure.

7. Short circuit: It is forbidden to contact the cathode and anode when the power is on. The instantaneous current caused by the short circuit is very large, which can burn the plate.

Seven, iridium mixed metal oxide coated titanium anode matters needing attention

1. Iridium metal oxide coated titanium anodes (referred to as iridium MMO coated titanium anodes) should be installed under the recommended electrolysis conditions.

2. Prevent oil or grease from contaminating iridium MMO coatings.

3. The iridium MMO coating is a ceramic coating with a porous surface and a larger specific surface area, and has good electrochemical properties. Iridium MMO is very easy to be scratched or damaged when a hard object rubs or knocks on its surface: it is forbidden to place the iridium MMO coated surface directly on the metal surface, and a protective paper or plastic film should be covered on the hard surface; Drag or slide the iridium MMO coated surface on any hard surface; if there is dirt or sediment on the iridium MMO coated surface, do not use any abrasive mechanical means to clean it. Do not use methods such as wire brushing, sanding, sandpaper or high pressure water jets to clean the anode surface.

4. When the titanium anode is removed from the plating tank, it should be rinsed with water immediately. To prevent acid corrosion, the acid concentration increases as the electrolyte dries out on the coating surface.

5. Titanium anodes that need to be stored for a longer period of time should be carefully packaged in, for example, air-filled plastic packaging to prevent scratches on the surface of the iridium MMO coating, or dust.

6. Applying an iridium MMO coating to the active portion of the titanium anode allows electrical current to be passed through the titanium anode coating surface into the electrolyte, while the uncoated titanium surface remains inert. If the small-area iridium MMO coating is mechanically damaged, the titanium under the coating is in direct contact with the electrolyte, and the titanium anode can continue to operate normally. Sexual oxide film.

7. There should always be a little distance between electrodes. An accidental short circuit between the titanium anode and the plated part can cause irreversible damage to the iridium MMO coating and can also damage the titanium substrate. In the event of a severe short circuit, the titanium anode can be completely destroyed.

8. The titanium anode must be in an anodized state as long as it is immersed in or in direct contact with the electrolyte. If the titanium anode is not energized, a low positive voltage (residual voltage) can be applied to the titanium anode. This simply applies 2 volts between the anode and the cathode, without using a power supply and a lot of current. Iridium MMO-coated titanium anodes are prohibited from being in an electrode-reversed state at any time.

9. Trace impurities such as lead, iron and barium in the electrolyte should be controlled. This will not generate a large amount of anode deposits. Anode deposits can clog the surface of the titanium anode and cause uneven anode current distribution.

10. Organic additives are added to the electrolyte, and different additives will have different effects on the life of the titanium anode. The life of iridium MMO-coated titanium anodes can be significantly shortened especially under the influence of additives or added oxides with synthetic properties.

11. Removal of Iridium MMO Coated Titanium Anode Surface Deposits

Hydrochloric acid - This acid is very effective in removing all forms of rust-like deposits and calcium-containing deposits. Because of its recovery characteristics, it can only be operated at room temperature, and a dilute solution with a concentration of 37% hydrochloric acid accounting for no more than 10% by volume is required. Because titanium anodes are still easily attacked by reducing acids such as hydrochloric acid, the time the anodes are in contact with them should be kept to a minimum, typically 10 minutes. In order to reduce the degree of hydrochloric acid attack, 0.1% ferric chloride can be added to the cleaning solution before cleaning. Note: After cleaning with hydrochloric acid, the titanium anode should be thoroughly cleaned with water, preferably fully immersed in water for at least 10 minutes.

Citric acid---At 40--50°C, 5-10% citric acid in water can be used to remove iron-containing precipitates. Again, rinse the anode carefully with water after cleaning.

Nitric Acid - Because nitric acid is an oxidizing acid, iridium MMO coatings are resistant to nitric acid at any temperature and concentration. However, since high-concentration nitric acid has strong oxidizing properties at high temperature, a titanium oxide film will be formed on the surface of the titanium substrate, and the conductivity of this film is very poor. nitric acid, but nitric acid at low concentrations and low temperatures is very useful for removing many precipitates that can form soluble nitrates, such as commercial nitric acid diluted to less than 10% and at room temperature.