Chromium plating process has many special features in addition to the common points with other plating types
Author: Anna
Chromium plating process has many special features in addition to the common points with other plating types:
① The main component of chromium electrolyte is not metal chromium salt, but chromic acid with strong oxidizing property.
② current efficiency is very low, generally 13 to 16%, the highest can only reach 23% or so, so in the process of chromium plating a large number of hydrogen precipitation, with toxic liquid fog, the need for good suction device and the use of chromium fog inhibitor.
③ The solution must add a small amount of additional anions, such as SO42-, F-, SiF62-, etc., but also in the electrolyte to maintain a certain amount of trivalent chromium.
④ The dispersing ability is low, and for parts with more complicated shapes, elephant anode, protective cathode, etc. must be used to get good plating layer.
⑤ The current density used is very high, sometimes tens of times higher than that of general plating. The tank voltage of the chromium plating process is also high, and it is often necessary to use a power supply of more than 12 volts, while other plating types can be used with a power supply of 6 volts.
⑥ Temperature and current density control requirements are strict, and the two should be closely coordinated. Current density is fixed, the temperature can only change 1 ~ 2 ℃, the temperature is fixed, the current density changes 2 ~ 3A / dm2.
⑦ The anode used for chromium plating is not metal chromium, but lead, lead-tin alloy or lead-antimony alloy and other insoluble anode.
⑧ because the chromium layer is easy to passivate, in general the plating process does not allow power cuts in the middle.
The above points, reflecting some of the characteristics of chromium plating production, that is, its specificity. This particularity constitutes the special nature of the chromium plating process as distinguished from other electroplating processes. However, chromium plating is a type of plating, it certainly has the general law of plating, we should start from the production practice, and gradually study and understand the whole process of chromium plating, understanding and mastering the chromium plating process of the special and universal laws, so that it can better serve the production.