The technical characteristics and correct use of platinum-coated titanium electrode products are as follows:
Platinum-coated titanium electrodes have four outstanding characteristics as anode materials:
- Strong corrosion resistance, durability and high temperature resistance, high stability, can be used in various media;
- The cost is lower than pure gold and pure platinum anode, but it has similar electrochemical performance;
- The overpotential is very high for the oxygen evolution reaction, and the overpotential is very low for the hydrogen evolution reaction;
- It has the characteristics of high output current density, uniform conductivity and small loss, and is suitable for DSA insoluble anode.
Correct use of platinum-coated titanium electrodes:
- Before using platinum-coated titanium electrodes, it is necessary to exclude (must be detected) the existence of “fluorine” ions and “phosphate” ions in the plating solution, and it is safe to confirm that there is no chemical composition that corrodes platinum-coated titanium electrodes. Use platinum-coated titanium electrodes, otherwise, the bottom substrate of platinum-coated titanium electrodes will be severely corroded, the platinum coating will fall off, and the service life will be shortened. Do not use hard chromium additives and recycled industrial chromic anhydride containing fluoride ions.
- Reasonable selection of the best process: the current density of the platinum-coated titanium electrode is preferably below 50A/dm2, and the tank pressure is below 10V, otherwise the service life will be affected, and the anode will be seriously corroded and dissolved, and the coating will fall off, try to choose The process of anodizing reaction without solid oxide formation avoids oxide thickening and passivation affecting the conductivity of platinum-coated titanium electrodes.
The reason for anode breakdown is determined by the inherent characteristics of the titanium material itself. When the cell pressure is greater than 10V, the titanium surface in contact with the platinum coating begins to dissolve slightly, and it breaks down completely at 12V. After the breakdown, the cell pressure we see can no longer be displayed. 12V can only see about 11V. At this time, the current can no longer be added, and the anode is damaged. Therefore, the pressure of the tank for safe use of platinum-coated titanium electrodes is set below 10V.
- In principle, the surface area of the cathode should be smaller than the effective anode area (that is, the anode area under the liquid surface). It should not be used when the anode area is smaller than the cathode area, otherwise the anode will be easily broken down and cannot be used normally.
- When the impedance of the plating tank increases, the tank pressure will also increase. When the tank voltage exceeds 10V, the current should not be increased, but the current should be adjusted appropriately, such as: the current is reduced by 10%, and the plating time is extended by 10%. .
There are many reasons for the increase in impedance, mainly as follows:
★The anodizing reaction will thicken and passivate the oxide layer with the passage of time;
★Because the titanium plate in contact with the busbar has a virtual contact or the surface of the titanium plate is passivated at high temperature;
★The content of the conductive medium in the plating solution is reduced;
★Anode breakdown, the bonding force between platinum layer and substrate is destroyed;
★The rectifier power supply is in poor contact with the busbar, etc.
Ways to improve electrical conductivity:
◆Remove the anode and keep it from water (that is, do not dry it), put it in 5% hydrochloric acid, soak it for 2 hours or more, and scrub the surface of the anode. Most of the lead chromate oxide will be washed off. If the effect is not satisfactory, the above steps can be repeated. After basic cleaning, rinse with tap water repeatedly, and finally rinse with deionized water to ensure that it does not contain fluoride ions before reuse. .
Another important point is to observe whether there is a breakdown phenomenon on both sides of the anode (that is, the platinum layer falls off). If it is serious, the anode cannot be used again. If one side is good and the other side is poor, the good side can be turned over and used;
◆Grind the titanium plate in contact with the copper bar to remove its passivation layer;
◆Appropriately increase the concentration of the plating solution;
◆Check whether the contact points of the power supply line are in good contact.
- After the anode is out of use, it is best to clean it with deionized water, take out the plating tank, and store it in a deionized water (or pure water) tank separately to prevent drying and protect the service life of the platinum-coated titanium electrode.
- Do not store in tap water for a long time, otherwise rust will adhere to the surface of the electrode and affect the use.