**1.3.4 Test of potentiodynamic anodic-polarization of the material in simulated physiological environment**

Figure 1-12 shows the polarization curves of TiNI SMA before and after cathodicelectrodeposition in Hank's solution (PH7.45). It can be seen from the anodic-polarization curves that the current density of the deposited sample is always lower than that of the one before depositing, even if at passive region, the current density of the deposited sample is similarly lower than that of non-depositing one, and the broken potential of the deposited sample was about 1.2V, and that of non-depositing one about 1.1V, thus the broken potential of the deposited sample was somewhat higher than that of non-depositing one. It can be seen from cathodic-polarization curves that the difference between the two samples' densities is not very great. This illustrates that the cathodically-electrodeposited sample in Hank's solution of PH7.45 has better properties of anodic-polarization and anti-corrosion, and the two properties are approximately close in cathodic-polarization. This is because of the Ti-O film existed on the surface of the deposited sample, with a protective role to substrate, that to a certain extent prevented Ni ions release from substrate, thus having a better corrosion resistance.

Figure 1-13 shows the polarization curves of TiNi SMA before and after cathodicelectrodeposition in Fusayama solution (PH6.13). It can be seen from the polarization curves in the figure that the current density of the deposited sample began to lower than that of non-depositing one from 0.3V, and even at passive region, the current density of the deposited sample was still lower than that of the one before depositing. It can be seen from cathodic-polarization curves that the difference between the two samples' current densities was not great. This also illustrates that because of the Ti-O film existed on the surface of the deposited sample with a protective role to substrate, that to a certain extent prevented Ni ions release from substrate, thus having a better corrosion resistance.

Fig. 1-12. The anodic-polarization curves of samples in Hank's solution (pH7.45)

Ti-O Film Cathodically-Electrodeposited on

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 15

a(40mA/cm2) b(30mA/cm2 )

c (20mA/cm2) d (5mA/cm2)

e (2mA/cm2)

Fig. 1-14. Optical microscope of Ti-O film by different current densities (1000×)

Fig. 1-13. The anodic-polarization curves of samples in Fusayama solution (PH6.13)
