Effects of temperature and span amplitude on fretting corrosion behavior of tin-plated electrical contacts

Fretting tests on electric contacts were conducted to investigate the effects of temperature and contact span amplitude on fretting corrosion behavior at 298 K, 323 K, 348 K and 373 K under a constant force of 0.85 N. Riders and flats made of 0.3 mm-thick brass sheet were coated with 10 μm of tin. The electric resistance was measured during the fretting test period. The electric resistance was very low; afterward, however, the resistance increased rapidly and intermittently with the number of fretting cycles. Electric failure lifetime (Nf) was found to decrease with increase in the testing temperature. It was assumed the failure cycle is a cycle with an electric resistance of 0.01 Ω. The damage rate (Ḋ) due to the degrading of the contact was inverse-linearly proportional to the number of cycles. A formula for lifetime prediction was developed by applying the Arrhenius equation. Using this formula, the lifetime can be predicted within a factor of two in a range below 35 μm span amplitude.