Official Answer
Answer
Fretting corrosion occurs at the contact points between the wave peaks and the mating surfaces, or between the turns of a nested spring, due to micro-oscillations (typically $< 100 \mu m$ amplitude). This removes the protective oxide layer of the stainless steel, leading to pitting and the formation of abrasive debris. In 17-7PH springs, this can lead to fatigue cracks nucleating at the pits. Prevention strategies include: 1) Increasing the preload to minimize relative movement; 2) Applying solid film lubricants (like $MoS_2$ or PTFE) to reduce the coefficient of friction; and 3) Surface hardening treatments like nitriding, although this must be balanced against the potential reduction in fatigue ductility.
