What are the signs of fretting corrosion in wave springs and how can it be prevented?

Fretting corrosion appears as reddish-brown (for steel) or black (for stainless) debris at the contact points between the wave crests and the mating surfaces. It is caused by microscopic oscillatory movements (vibration) that break down the protective oxide layer of the metal. This not only wears the spring but also creates pits that act as stress risers, leading to fatigue failure. Prevention strategies include increasing the axial preload to minimize movement, applying a sacrificial coating like silver or tin, or using a dry film lubricant to reduce the friction coefficient at the interface.