Nickel coated with titanium oxide

Figure 3 Behavioral pattern of nickel specimens coated with titanium oxide following sequential treatments in hydrogen, acetylene and oxygen.

The advantages of using chloride electrolytes compared with sulfate electrolytes are higher electrical conductivity, lower electrolyte viscosity, lower overpotential for nickel reduction, and higher solubility and activity of nickel. An important factor is the lower anode potential of chlorine evolution compared with oxygen evolution in sulfate electrolytes using the common lead anodes. Chloride electrolytes require insoluble or dimensionally stable anodes, usually titanium coated with an electroactive noble metal or oxide, and a diaphragm system to collect the CI2 gas from the anode. The chlorine liberated at the anode is recycled for use in the leach circuits. In practice, some decomposition of water... 

New types of anodes (cement overlays with bare or nickel-coated carbon fibres, sprayed titanium coatings, ceramic conducting oxides, etc.) have been used for a few years, but the experience achieved is stiU inadequate to define their rehability over long periods. 

Term 3. Titanium anodes coated with oxides of Ir, Ru or Pt are generally used in membrane cells and lead to a chlorine overvoltage of approximately 0.05 V at 3 kA/m. Hydrogen overpotentials of about 0.1 V at 3.0 kA/m are attained with activated cathodes. Mainly nickel substrates are coated by painting and thermal treatment or galvanic deposition [138], [139]. Coating materials include Ni, Co, Ru and others (see Section 8.2). 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

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