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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