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Chrome key feature
Jan 13, 2017

① main ingredient is not metal chromium plating chromium salts, acid – chromic acid containing oxygen instead of chrome, belongs to the strong acid bath. The electroplating process, cathodic process complex, cathodic current consumption in most hydrogen and hexavalent chrome reduced to trivalent chromium on both side, chrome-plated cathode current efficiency is very low (10%~L8%). And there are three exceptions: current efficiency decreased with increasing the concentration of chromic anhydride l drops as temperature rises; increases with increasing current density.

② in chromium plating, you must add a certain amount of anions, such as SO42-, SiF62, f, first, to achieve normal deposition of chromium metal.

③ plated chrome disperse very low for parts with complex shape, Conformal anode or auxiliary cathode is needed, to obtain a uniform layer of chrome. Of rack requirements are more stringent.

Black Chrome-plated cathode current density to be high, usually above 20A/dm2, l0 times more than ordinary plating above. Due to extremely large precipitation cathode and anode gas bath resistance is large, tank pressure, high requirements on the electroplating power supply needed power greater than l2V, while other plating types use the 8V power supply.

⑤ anodes for chromium metal chrome plated, and adopting insoluble anode. Commonly used, lead-antimony alloy of lead and lead-Tin alloys. Bath due to deposit chromium consumption or other reasons need to be supplemented by adding chromic anhydride.

⑥ chrome operating temperature and cathodic current densities have certain dependencies, change the relationship between different properties of chromium plating.


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