Corrosion resistance of implant materials

 Experiment purpose

      This experiment aims to measure the corrosion resistance of two metal implants in simulated body fluid. The metal implants are mesh disk woven with wire after surface treatment - black and red.

Preparation

- Potentiostat CS350M

- Reference electrode: SCE CS900     

- Counter electrode: Pt electrode CS911

 - Samples/Working electrode: metal wire mesh disk (black and red) 

- Solution: simulated body fluid (SBF) (pH=7.4)

Steps:

Insert the counter electrode, reference electrode, salt bridge, and exhaust pipe into a 500 mL electrolytic cell, and fill the cell with 350 mL simulated body fluid, and then place the electrolytic cell in a 37 ℃ water bath. Purge N2 into solution for 30 min, seal the air outlet to prevent oxygen from entering again.

Potentiodynamic test
      After the OCP is stable, we can start to measure the passivation curve. It sweeps from -0.1V to 1V (vs. OCP). When the anode current is greater than 100 mA/cm2, the potential’s scan will be reversed.

Fig 1. Parameters setting window

Result and analysis 

Fig. 2. Passivation curve of the two specimens

In the red curve, the breakdown potential is 0.14754 V, the OCP is -0.00734 V. For the black specimen, the breakdown potential is 0.24004 V and the OCP is -0.00222V. The lower breakdown potential of the red curve indicates that the sample's resistance to pitting corrosion is inferior to that of the black sample.

 However, the smaller hysteresis loop area formed during the reverse scan of the red curve suggests that the red mesh material can repair more rapidly after the passive film is destroyed, demonstrating its stronger self-healing capability.