Editing Electroplating (section)

==Alternatives to electroplating==

There are a number of alternative processes to produce metallic coatings on solid substrates that do not involve electrolytic reduction:

* [[Electroless Deposition|Electroless deposition]] uses a bath containing metal ions and chemicals that will reduce them to the metal by [[redox reaction]]s.  The reaction should be [[autocatalysis|autocatalytic]], so that new metal will be deposited over the growing coating, rather than precipitated as a powder through the whole bath at once.  Electroless processes are widely used to deposit [[Electroless nickel-phosphorus plating|nickel-phosphorus]] or [[electroless nickel-boron plating|nickel-boron]] alloys for wear and corrosion resistance, [[Tollens' reagent#In silver mirroring|silver]] for [[mirror]]-making, [[copper]] for [[printed circuit board]]s, and many more.  A major advantage of these processes over electroplating is that they can produce coatings of uniform thickness over surfaces of arbitrary shape, even inside holes, and the substrate need not be electrically conducting.  Another major benefit is that they do not need power sources or specially-shaped anodes.  Disadvantages include lower deposition speed, consumption of relatively expensive chemicals, and a limited choice of coating metals.
* [[Immersion coating]] processes exploit [[displacement reaction]]s in which the substrate metal is oxidized to soluble ions while ions of the coating metal get reduced and deposited in its place.  This process is limited to very thin coatings, since the reaction stops after the substrate has been completely covered.  Nevertheless, it has some important applications, such as the [[electroless nickel immersion gold]] (ENIG) process used to obtain gold-plated electrical contacts on printed circuit boards.
* [[Sputtering]] uses an electron beam or a plasma to eject microscopic particles of the metal onto the substrate in a vacuum.
* [[Physical vapor deposition]] transfer the metal onto the substrate by evaporating it.
* [[Chemical vapor deposition]] uses a gas containing a volatile compound of the metal, which gets deposited onto the substrate as a result of a chemical reaction.
* [[Gilding]] is a traditional way to attach a gold layer onto metals by applying a very thin sheet of gold held in place by an [[adhesive]].
[[File:Luigi Valentino Brugnatelli. Stipple engraving by F. Bordiga Wellcome V0000839.jpg|thumb|upright|[[Luigi Valentino Brugnatelli]]]]