How does Fretting Corrosion manifest in wave springs and what is the remedy?

Fretting corrosion appears as reddish-brown (for steel) or black (for stainless) debris around the contact points of the wave crests. It is caused by small-amplitude oscillatory motion between the spring and the mating surface. This motion removes the protective oxide layer, leading to continuous oxidation and wear. In aerospace actuators, this can lead to 'frozen' assemblies. The remedy is to increase the preload to stop the movement or to plate the spring with a sacrificial or lubricating layer like Silver or Cadmium (where permitted).