Official Answer
Answer
Fretting corrosion occurs at the contact points (peaks) between adjacent turns of a multi-turn spring or between the spring and the mating plates. It is caused by micro-oscillations (vibration) that break down the protective oxide layer of the metal. In stainless steels, this exposes fresh metal which then oxidizes, creating a cycle of wear and oxidation that results in 'pitting.' This can lead to stress concentration and eventual fatigue failure. To prevent this, we apply anti-fretting coatings like Silver plating or PTFE. Additionally, increasing the initial preload can 'lock' the contact points in place, preventing the relative micro-movement that drives fretting.
