What anode do we typically use when working with decorative chrome additives?
Unlike normal electroplating, decorative chromium plating uses insoluble anodes such as lead and lead alloys, which is determined by the specificity of the chromium plating process.
If chromium is used as an anode in chromium plating, the following 2 disadvantages will result:
① The anode current efficiency is close to 100%, the high cathode current efficiency is only 8-13%, and the concentration of chromium is constantly increasing.
② Chromium plating is directly reduced by hexavalent chromium, and the chromium dissolved in the chromium anode into different valence states, and mainly to trivalent chromium, which will lead to a rapid increase in trivalent chromium, and the hexavalent chromium continues to decrease, resulting in failure.
In addition, chromium metal is very brittle and difficult to shape and machine. Which means it's hard to get a proper chrome anode.
Therefore, when the plating factory uses decorative chromium additives, it will use pure lead, lead-antimony or lead-tin alloy as the anode depending on the composition of the plating solution. The plating solution containing silicofluoric acid is highly corrosive to the anode, and the pure lead is easy to corrode and dissolve, and the lead alloy containing antimony or tin 6-8% has good corrosion resistance, which is widely used in production.
In normal production, the lead anode is covered with a yellow film of lead dioxide, which does not affect electrical conductivity.
When the plating is stopped, if the lead or lead alloy anode is not removed, the lead dioxide will be converted into lead chromate in the chromic acid solution, which is dense and has poor electrical conductivity, resulting in increased tank voltage and increased power consumption. Therefore, it is better to remove the anode in a clear sink when we stop plating.
When customers use Bigely decorative chromium additive Cr-8, they use a lead-tin anode, which is operated according to the process parameters, which helps to plate a chrome-plated layer with good location and fine crystallization.
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