Many other types of nickel plating solution have been advocated, mostly based on nickel sulfate, although nickel chloride and nickel sulphamate baths can be worked more quickly. All these yield matt deposits and are called dull plating baths. The electroplated coating from the Watt bath is smooth but of a matt, pearly milk-white texture and must be mechanically polished if, as is usual, a high luster is required. This process is called coloring or color buffing, and is fairly readily accomplished by pressing each part of the surface of the article against a revolving wheel built up of soft cloth discs. The wheel is dressed with very fine lime or similar powder bound in grease, the powder flowing or smearing the surface rather than abrading it.
The major modern change in the practice of nickel plating has been the use of brightening and leveling additions to the nickel plating solution of the
In addition to its use as undercoating to chromium, nickel plating is often used alone fro protection of chemical plant and food processing equipment, or parts, such as the electrodes of thermion valves, which must be protected from scaling by the action of heat.
Thicker deposit of electrodeposited nickel are sometimes applied to worn or wrongly machined steel parts to restore them to size or make them oversize. In such cases great attention must be paid to the preliminary etching process, to ensure good adhesion, and to the mechanical properties of the electrodeposited coating. The deposit can be confined to specific areas of the steel part by applying a thick layer of adherent and chemically neutral wax to the remaining area. This is called stopping off and is also used to prevent unwanted plating on the shaft of suspension jigs, etc. in decorative plating.