Depolarized nickel anodes
Anodes of high purity (> 99 % Ni) and contain precisely dosed additives of other elements such as sulphur, carbon, oxygen or silicon, which increase the solubility of the anodes or reduce their passivity or polarity. They are used in the form of rolled anodes, billet anodes, nickel squares, nickel crowns, nickel rounds or nickel pellets.
Nickel anodes with an addition of 0.025 wt.% sulphur or 0.05 to 0.2 wt.% oxygen prevent polarisation, i.e. the passivation of the anodes. S-depolarized nickel anodes are frequently used in electroforming. These are highly soluble in Ni sulphamate baths, do not passivate and reduce the risk of accumulation of anodic oxidation products of sulphamic acid, in particular azodisulfonate (ADS) in the electrolyte. ADS in increased concentration causes sulphur incorporation in cathodically deposited nickel, which can be advantageous or disadvantageous. S-nickel is also available in the form of nickel squares, nickel crowns, nickel rounds or nickel pellets.
These can be poured into preformed titanium anode baskets, have a very large surface area and produce a favourable anode-cathode ratio (large anode areas also reduce the risk of passivation (depolarisation), for example).
The risk of passivation of nickel anodes (anodic polarization) can also be reduced by adding chloride ions to the electrolyte.