from microscopic pores that occur in the gold at thin plating thicknesses. These pores, when
they extend to the base contact material, can form corrosion products on the surface of the
plating. However, when a nickel underplate is used, the nickel is exposed in these pores and we
can take advantage of the inherent self-passivation properties of nickel to limit corrosion
products from forming. Without the nickel barrier, corrosion will inevitably form and degrade
the contact interface. Experienced connector suppliers with a long background in contact
physics have finely tuned plating systems and coatings that mitigate the effects of pore
corrosion.
Figure 4. Nickel prevents corrosion from migrating through micropores from the base material
through gold plating to the surface.
As one might expect, non-noble platings—typically tin, nickel, and silver— are subject to
corrosion. Tin and tin alloys dominate as non-noble contact platings. When a connector is
correctly designed and the appropriate environmental considerations are made, tin plating
systems can form a very durable and cost-effective interface for most applications.
Non-noble platings are typically applied in a thicker layer to ensure adequate barrier properties
and require higher normal forces to break through the inevitable non-conductive oxides that will
form on the surface. The exception to this is silver-based platings where the oxides are relatively
