In the production of hard chrome additives, we should try our best to prevent trivalent chromium from rising. The reason is that the trivalent chromium is low, just add the appropriate amount of reducing agent can make the hexavalent chromium reduced to trivalent chromium, such as hydrogen peroxide, ethanol (that is, industrial alcohol), oxalic acid and so on. Adding oxalic acid is easy to quantitatively calculate: theoretically 10g/L oxalic acid can produce 2.75g/L trivalent chromium. Using hydrogen peroxide is not so good, and you have to add heat to the process to let it evaporate.
Trivalent chromium is very difficult to remove, can only use a large area of lead alloy as the anode, a small area of iron rods and so on as the cathode, a long time electrolysis (diaphragm electrolysis is more troublesome), so that the trivalent chromium oxidized to hexavalent chromium in the lead alloy anode.
Trivalent chromium is easily oxidized to hexavalent chromium only on lead and lead alloys, which is actually a layer of lead peroxide film layer generated on the surface of the anode during the electrolysis process, which enables the oxidation of trivalent chromium to continue. (If there is a small amount of hexavalent chromium in the trivalent chromium plating solution, no chromium can be plated, so lead and lead alloy are not allowed to be used as anode.)
The anode used for chromium-plating additives is generally pure lead, the surface is prone to lead chromate, and should be taken out frequently for scrubbing. Lead-antimony alloy anode, although high strength, but corrosion resistance than lead-tin anode is poor, so now more than not use lead-antimony alloy and lead-tin alloy. Tin content of only 8% or so of the lead-tin alloy is not enough to prevent the rise of trivalent chromium in the plating solution, and the tin content should be (18~20)%.
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Guangdong Bigely Technology Co., Ltd. ,founded in 2003, is a high-tech enterprise integrating R & D，production, sales and service, specializing in the production of electroplating additives. As a famous electroplating additives source manufacturer in China, Bigely has over 20 years' experience in electroplating additives production and own production base of 5000 square meters. We can produce 15,000 tons of electroplating additives every year, which can fully meet the needs of customers.
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