Corrosion resistance of implant materials

Corrosion resistance of implant materials

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

Preparation
Reference electrode: SCE

Counter electrode: Pt electrode
Working electrode: metal 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 physiological solution, and then place the electrolytic cell in a 37 ℃ water bath. Purge N2 into the simulated body fluid for 30 min, seal the air outlet to prevent oxygen from entering again.

Result and analysis
Turn on the CS350M electrochemical workstation, start the CS Studio software, and monitor the open circuit potential(OCP). After the OCP gets 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. The parameters’ setting is shown in Figure 1, and the results are shown in Figure 2.

Fig 1. Parameters setting window

Fig. 2. Passivation curve of the two specimens

(red/black curve line represent corresponding red/black specimen)

In the red curve, the breakdown potential is 0.14754 V, the OCP is -0.00734 V. The breakdown potential is 0.24004 V and the OCP is -0.00222 V for the black specimen. It suggests that the black specimen behaves better for pitting resistance abilities. But the area of the hysteresis loop is smaller for the red sample during the flyback, indicating that the red specimen can be quickly repaired after the passivation film is destroyed, that is, its self-healing ability is stronger.