Some features of the Chrome Plating Process
In addition to the chrome plating process in common with other types of plating, there are many special places:
①The main component of the chrome-plating electrolyte is not metal chromium salt, but chromic acid with strong oxidizing properties.
② The current efficiency is very low, generally 13-16% and the highest can only reach about 23%. Therefore, a large amount of hydrogen is precipitated during the chrome plating process, bringing out toxic liquid mist, which requires a good air suction device and the use of chrome mist inhibitors.
③ A small amount of external anions must be added to the solution, such as SO42-, F-, SiF62-, etc., and a certain amount of trivalent chromium must be maintained in the electrolyte.
④ Low dispersion ability. For parts with complex shapes, pictographic anodes, protective cathodes, etc. must be used to obtain a good coating.
⑤ The current density used is very high, sometimes dozens of times higher than the current density of general plating. The tank voltage of the chrome plating process is also high, and a power supply of more than 12 volts is often required, while other types of plating use a power supply of 6 volts.
⑥ The control requirements of temperature and current density are strict, and the two must be closely coordinated. When the current density is fixed, the temperature can only change by 1 to 2°C. When the temperature is fixed, the current density changes by 2 to 3A/d㎡.
⑦ The anode used for chrome plating is not metal chromium, but insoluble anodes such as lead, lead-tin alloy, or lead-antimony alloy.
⑧Because the chromium layer is easy to passivate, it is not allowed to be cut off halfway during the electroplating process under normal circumstances.
The above points reflect some of the characteristics of chrome production, that is, its particularity. This particularity constitutes the special essence of the chrome plating process that distinguishes it from other electroplating processes. However, chrome plating is a kind of electroplating, and of course, it also has the general laws of electroplating. We should start from production practice, gradually study and understand the whole process of chrome plating, understand and master the special and general laws of the chrome plating process, and make it Better serve the production.
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