Effects of Surface Treatment on Corrosion Resistance of 316 Stainless Steel Implants in Tyrode Solution

Abstract The effect of different surface preparation methods such as mechanical, chemical, and electrochemical surface preparation as well as ultrasonic cleaning on the formation, stability, and deterioration of surface films formed on austenitic 316 stainless steel was investigated in Tyrode's solution. The methods of cyclic polarization, AC impedance measurements and surface techniques were used. A hysteresis loop in a cyclic polarization curve was obtained that indicates a delay in re-passivation of an existing pit when the potential is scanned cathodically. Nyquist diagrams consist of two strongly overlapped capacitive semicircles which are assigned to charge transfer and passive film resistance. Electrolytic polishing improves corrosion resistance by increasing the value of the corrosion potential and breakdown potential of the passive layer as well as the pit initiation potential. After chemical passivation and acid cleaning, no perfect passivation region was observed. Change in surface fractal is in good agreement with the result obtained from height roughness factor of AFM.