The effects of thin polymeric surface films on fretting corrosion

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Virginia Polytechnic Institute and State University


The main purpose of this research is to determine if polymer films can prevent fretting between two metals, and if they can, what the protection mechanisms are. This research is a part of fretting corrosion studies currently funded by the Army Research Office. Four thermoplastic polymers were tested for their effectiveness. Two other independent variables were also tested: plate hardness and plate roughness. A ball-on-plate device was built to approximate point sliding at the fretting corrosion interface. The tribometer has two experimental positions that are electrically insulated from the rest of the apparatus so that an electrical circuit could be used to monitor metal-to-metal contact. All experiments were run with 52100 steel balls, 1040 steel plates, a normal load of 45 N (10 lbf), an amplitude of .33 mm (.013 in.) and a frequency of 20 Hz. PVC films were found to prevent fretting and metallic contact for 40 minutes. An electrochemical fretting corrosion mechanism has been suggested to explain this behavior. PTFE, LDPE, and PSF films could all produce fretting corrosion while preventing metal-to-metal contact for 40 minutes. Plate hardness and plate roughness had no statistical significance on the measured minimum fretting friction force.