Causes and prevention methods of interlayer of Electrodeposition nickel
Generally speaking,Electrodeposition NickelIn consumption, there are usually the following reasons for the cathode to present the mezzanine:
In the process of ① electrolysis, the cathode surface is polluted, or because of the change of liquid supply conditions, the local ph is too high, so the hydrogen oxide is produced on the cathode, or because of the influence of impurities to produce local bursting skin, these phenomena will lead to the presentation of the mezzanine.
② when the organic matter in the solution is too high, the metal contains iron, zinc, or the hydrogen analysis is serious, so that the internal stress of the accumulation increases and the bursting skin curls.
③ before the surface of the lower groove is not disposed of clean, still have organic matter, or cover up a layer of oxides, nickel salt and other films, resulting in electrolytic newly stacked nickel can not be well bonded with the beginning of the pole and produce stratification.
In the process of ④ electrolysis, it is easy to form a mezzanine when the current lift is too hasty or the power outage is too long.
The consumption theory of a nickel electric product consumption line in China indicates that "mezzanine"Electrodeposition NickelMainly wet interlayer, nickel plate on the upper and lower edges and side of the surface of the open, some of the plate is intact without cracking but there is a solution dripping from the stomata. Several times presented during the trial consumption processElectrodeposition NickelThe interlayer problem has the common characteristic that the bursting skin and the interlayer electrodeposition nickel are present in the diaphragm bag (pH≥5.0) with high PH today, and the inner wall of the diaphragm bag is observed to have serious blockage phenomenon, and the inner wall clings to a layer of green solid particles. Therefore, the high ph of the solution in the diaphragm bag is the main reason for the accumulation of nickel interlayer.
The situation of interlayer electrodeposition of nickel presented in consumption
Ensuring the ph stability of the solution in the diaphragm bag will effectively reduce the output of the sandwich nickel Plate. In the consumption process, there are many factors that affect the ph change of the solution in the diaphragm bag, such as diaphragm bag material, Yang Ji acid response, new liquid composition, and so on, and many elements interact and interact with each other, so the consumption control needs comprehensive thinking.
The effect of ① diaphragm bag material. Nickel electrolysis usually has a certain plea to the wettability, filtration performance and material of the diaphragm bag. Diaphragm bags must be pre-disposed before use to improve (a) interlayer electrodeposition of nickel; (b) diaphragm bag inner wall paste bag phenomenon
Its properties and removal of substances on the diaphragm bag that have an impact on the electrolysis process. Some diaphragm bags because the quality does not reach the plea, often after disposal still affect the quality of electrolytic products, diaphragm bag penetration ability is weak, h+ can not reverse seepage, and in the cathode consumption of h+ faster than the speed of the supplement, the ph in the bag will gradually rise, and eventually lead to the nickel surface blackened or generated Shiyan, affecting the quality of nickel. There are great differences in the application of the diaphragm bag of polyester cotton or new coating film at present. Table 9-3 is the result of the suspension of field experiments under the same consumption conditions for several diaphragm bags consumed by different materials and preparation methods. After experimental comparison, the ph of the solution in the diaphragm bag consumed by different materials or preparation methods has a large gap, and the high ph of the bag is characterized by laminated nickel; With regard to the diaphragm bag with strong penetration ability, the difference of liquid level inside and outside the diaphragm bag fades, the h+ in the anode area seeps into the diaphragm bag under the action Instead, it constitutes an electric nickel producing gas lone L. Therefore, it is necessary to select a medium permeability diaphragm bag to ensure that the ph of the cathode liquid in the diaphragm bag is stable within the technical conditions, and to eliminate the influence of the diaphragm bag material on the electrodeposition of the nickel interlayer. ② the effect of current density. According to the Tafer equation 77=n+ blgj (with Overcurrent, j is current density, mouth, 6 as constant), it can be seen that the super-potential and current density are linear, increasing the current density, can increase the super potential of nickel and hydrogen at the same time. When the current density decreases, the hydrogen over potential is bound to decrease, which is also conducive to the suspension of hydrogen response. However, the high current density will make the super potential of nickel increase faster than the super potential of hydrogen, which is beneficial to the precipitation of hydrogen.
Consumption theory indicates that when the current density is less than the A/RTI2, about the newly opened groove, diaphragm bag regardless of good permeability and bad, after the power through the 4~5 h electrolytic consumption, diaphragm bag solution ph from 2.5-3.0 before the electricity rise to 5. o above. If it is maintained at low current density for a period of time, a layer of green solid particles will be generated in the inner wall of the bag, followed by the phenomenon of electro-nickel bursting and interlayer.