Arc Damage and Intermetallic Growth Can Combine in High-Resistance Contacts

What the evidence preview establishes

Localized electrical arcs damaged the contact surfaces, while extensive nickel-tin, copper-tin, and zinc-tin intermetallic growth consumed much of the metallic tin. Permanent deformation reduced contact force. Hot mating or excessive operating current better explained the combined damage than a single isolated plating flaw.

Why this case matters

High contact resistance can become self-reinforcing: low force and intermetallic growth raise resistance, heat accelerates degradation, and arcing removes the remaining protective surface. Powered and unused contacts provide an essential comparison.