Surface Coating Technologies

Besides manufacturing contact materials from the solid phase, i.e. by melt or powder metallurgy, the production starting in the liquid or gaseous phase is generally preferred when thin layers in the μm range are required which cannot be obtained economically by conventional cladding methods. Such coatings fulfill different requirements depending on their composition and thickness. They can serve as corrosion or wear protection or can fulfill the need for thin contact layers for certain technical applications. In addition they serve for decorative purposes as a pleasing and wear resistant surface coating.

Table 7.1: Overview of Important Properties of Electroplated Coatings and their Applications

To reduce the mechanical wear of thin surface layers on sliding and connector contacts additional lubricants in liquid form are often used. On silver contacts passivation coatings are applied as protection against silver sulfide formation.

7.1 Coatings from the Liquid Phase

For thin coatings starting from the liquid phase two processes are used differentiated by the metallic deposition being performed either with or without the use of an external electrical current source. The first one is electroplating while the second one is a chemical deposition process.