Nickel Plating

The electrolytic nickel plating is mainly used today. Are placed objects from nickel (well cleaned with mechanical brushing or washing with alkaline solutions that degrease them) as a cathode in an electrolytic bath, they are immersed in the same bath (respecting certain geometrical principles) some of the metal bars to be deposited , connected to the anode. When feeding the current, the positive ions of the metal to deposit migrate towards the negative pole, where downloading deposited in the form of a continuous metal layer. To the positive pole is, instead, the dissolution of the metal with the formation of ions in solution, ranging in reintegrate the downloaded ions to the cathode. The overall reaction is a redox, as a result of anodic oxidation of the metal that melts losing electrons, and the cathodic reduction of the ion that is deposited as metal electrons. La acquiring resistance to corrosion that is tied more than the thickness of the layer, to its porosity, brittleness, adherence, etc. The mechanical cleaning of an electrolytic deposit mostly exerts a beneficial effect on the resistance to corrosion, as well as appropriate pairs copper-nickel-chromium considerably increasing the protective value of the coating by reducing much of the number of pores. It is well known that every galvanic deposit is more or less porous. For the nickel we have tried to overcome the drawback with the most different methods. The simplest is to provide relevant thicknesses (at least higher than 50 m m) under suitable electrochemical conditions. This method involves, obviously, a certain considerable consumption of nickel.

The porosity is also fought with other systems based on the variation of the current density, on the superposition of an alternating current to the continuous, on the electrodeposition of two or three layers of nickel, on the electrodeposition encapsulating inert particles (alumina, titanium dioxide, silica, etc. .) and the assistance of ultrasound.
In general, to economically obtain the most compact coatings on ferrous material in order to protect it in the best way from corrosion, it is recommended the adoption of the double-copper-nickel layer, in which, however, the copper film thickness must be at least 50% of that of nickel.