Electrolytic nickel plating. Specifications

Electrolytic nickel coatings, produced by electrolysis of aqueous solutions of different types of salts, depending on the application and the characteristics of the coatings to be produced, represent a major industrial activity: consumption of electrolytic nickel far exceeds that of the other metals traditionally used industrially for other types of electrolytic coatings, such as copper, chromium, zinc, etc.

Nickel plating combined with chromium plating is the most common surface coating used to maintain the decorative appearance of plated parts. Since the development of bright nickel plating baths, nickel is also widely used directly, without mechanical polishing, as an undercoat in combination with chromium for a variety of applications: furniture, plumbing, decoration, automotive, sporting goods, etc. Although its reflections are different from those of electroplated chromium (detectable by trained eyes), a similarity in appearance also favors its use as an undercoat to compensate for any defects that may occur during decorative chromium plating or that may appear during use.

Along with other more noble metals (palladium, rhodium, platinum or gold), it was widely used in jewelry until it was suspected of causing health problems. Its prohibition as an undercoat makes it necessary to develop alternative processes, and studies are currently underway.

Other applications for nickel deposits, always as a sub-layer, are in the field of connectors, where it is used as a base for deposits of metals such as gold, in particular to avoid diffusion into the substrate and for cost reasons.

Finally, electrolytic nickel is used in very thick deposits (several hundred micrometers) in electroforming, for mold making, for example, or in hardfacing to restore the dimensions of certain parts, in addition to or in parallel with thermal spraying or welding methods.

This first article covers the general principles of nickel plating, surface preparation and the structure, properties and applications of deposits. The implementation of electrochemical nickel plating is the subject of a second article.