How does 'Fretting Corrosion' occur in wave springs and how can it be mitigated in subsea couplings?

Fretting corrosion occurs at the contact points between the wave spring and the mating surfaces (or between turns of a multi-turn spring) when subjected to low-amplitude, high-frequency vibration. The small relative motion removes the protective oxide layer (e.g., the Cr2O3 layer on stainless steel), leading to rapid oxidation and the formation of abrasive debris (red rust on carbon steel, black powder on stainless). This debris accelerates wear and can lead to premature failure. In subsea couplings, this is mitigated by using Inconel X-750 and applying a solid-film lubricant like Molybdenum Disulfide (MoS2) or a silver plating. The lubricant reduces the coefficient of friction and prevents the metal-to-metal contact that drives fretting.