Fretting corrosion characteristics of electrodeposited and hot dipped tin coating contacts

Electrodeposited (ED) tin was coated on the copper substrate for electrical contact instead of conventional hot dipped (HD) tin and subjected to fretting tests. The fretting wear behavior was investigated with various fretting cycles at ± 25 μm displacement amplitude, 0.5 N normal load, 3 Hz frequency, 45-50% relative humidity, and 25 ± 1 °C temperature. The contact resistance variation was recorded with fretting cycles. The fretting corrosion performance of ED tin enhanced with that of HD tin. The grain structure of ED tin was not removed even at 9000 fretting cycles, whereas HD tin removed at 1000 fretting cycles. The interdependence of extent of wear and oxidation on the fretted zone increases the complexity of the fretting corrosion behavior. The extent of wear and the elemental distribution at the center and edges of the fretting zone was characterized using scanning electron microscope (SEM) and energy dispersive analyzer of X-ray (EDAX). The surface profile of the fretted surface was examined using laser-scanning microscope (LSM). The fretting behavior difference between ED tin and HD tin was correlated to the grain structure as well as the absence of the abrasive debris in ED tin.