Transient electric fields induced by mechanically assisted corrosion of Ti-6Al-4V

Samples of Ti-6Al-4V were immersed in physiological solution and abraded via an electrochemical scratch method to observe the development of transient electric fields a finite distance from the scratch event. Transient electric fields were detected near both potentiostatically held and freely corroding samples. Transient currents measured by a potentiostatically held PtIr microelectric probe near a potentiostatically held sample were opposite in sign to those of the mechanically induced sample currents and were found to change character with sample potential, probe potential, and distance from the scratch event. Transient probe currents measured near a freely corroding sample were of the opposite sign as the sample transient near the primary site of oxidation, but were of the same sign near the primary site of reduction. The measured transients are a direct result of the electrochemical processes ongoing during oxide fracture and repassivation and can be sensed several millimeters remote from the abrasion site. A model for the generation of these fields is presented. Possible effects that these potentials may have on cellular structures surrounding an implant are proposed.