Operating and Maintenance Instructions for Ruthenium-Iridium Mixed Metal Oxide Coated Titanium Anodes

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

2. Avoid oil or grease contamination of iridium MMO coating.

3. Ruthenium-iridium MMO coating is a ceramic coating with porous surface and large specific surface area, and has good electrochemical performance. Ruthenium-iridium MMOs are very susceptible to scratching or damage when a hard object rubs or hits the surface.

A. It is forbidden to place the iridium MMO coating surface directly on the metal surface. Hard surfaces should be covered with protective paper or plastic film.

B. It is forbidden to drag or slide the iridium MMO coated surface on any hard surface.

C. If there is dirt or deposits on the surface of the ruthenium-iridium MMO coating, it is forbidden to use any abrasive mechanical means to clean it. The use of wire brushes, sandpaper, sandpaper, or high-pressure water jets to clean the anode surface is prohibited.

4. After the titanium anode is taken out from the electrolytic cell, it should be rinsed with water immediately. To prevent acid corrosion, the acid concentration increases as the electrolyte on the coating surface dries out.

 5. Titanium anodes that need to be stored for a long time should be carefully packaged, such as inflatable plastic packaging materials, to avoid scratches or dust on the surface of the ruthenium-iridium MMO coating.

6. Coating ruthenium-iridium MMO coating on the active part of the titanium anode can make the current pass through the surface of the titanium anode coating to reach 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 work normally. Oxide film.

7. Always keep a certain distance between electrodes. Accidental shorts between the titanium anode and the plated part can cause irreparable damage to the ruthenium-iridium MMO coating, as well as damage the titanium substrate. In the event of a severe short circuit, the titanium anode can be completely destroyed.

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

9. The content of lead, iron, barium and other impurities in the electrolyte should be controlled. This does not produce significant anode deposits. Anode deposits can clog the titanium anode surface and cause uneven anode current distribution.

10. Organic additives are added to the electrolyte. Different additives will have different effects on the life of the titanium anode. The lifetime of iridium MMO-coated titanium anodes can be significantly shortened by additives or by adding oxides with synthetic properties.

11. A method for removing deposits on the surface of a ruthenium-iridium MMO-coated titanium anode.

A. Hydrochloric acid - This acid is very effective in removing all forms of rust-like deposits and deposits containing calcium. Due to its reducing properties, it can only be operated at room temperature, and a dilute solution with a concentration of 37% hydrochloric acid not exceeding 10% by volume is required. Since the titanium anode is still easily attacked by reducing acids such as hydrochloric acid, the time for the anode to be in contact with it should be minimized, generally 10 minutes. In order to reduce the corrosion degree of hydrochloric acid, 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.

B. Citric acid - at a temperature of 40-50 °C, 5-10% citric acid aqueous solution can be used to remove iron-containing precipitates. The anode was carefully rinsed with water after washing the precipitate.

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