**1.3.3 Corrosion potential test of the materials in simulated physical environment**

Figure 1-10 shows a relation of corrosionpotential-time of the samples before and after depositing in Hank's solution (PH7.45). It can be seen from the figure that the corrosion potential of the deposited sample dipping in solution went down quickly, about 5 minutes after, the corrosion potential did basically not change any more, stabilizing at -0.4V. Furthermore the stable corrosion potential was more positive than the non-depositing sample's, at about -0.2V. This illustrates that the deposited sample has a higher thermodynamic stability than the non-depositing sample's one at PH7.45 in Hank's solution.

Figure 1-11 shows a graphofarelation of corrosionpotential-time of the samples before and after depositing in Fusayama solution (PH6.13). It can be seen from the figure that the corrosion potential of the deposited sample dipping in solution went down quickly also, 7 minutes after, basically stabilizing, although somewhat undulating, the potential did not change on the whole, keeping at -0.12V. But the non-depositing sample's potential basically stabilized at -0.15V, which was more negative than the deposited one's. This illustrates that

Ti-O Film Cathodically-Electrodeposited on

**physiological environment** 

better corrosion resistance.


E/V(SCE)

the Surface of TiNi SMA and Its Bioactivity and Blood Compatibility 13

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

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

012345

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

l g i / n A c m - <sup>2</sup>

1.

2.

ions release from substrate, thus having a better corrosion resistance.

1. treated 2. untreated

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

the deposited sample has a higher thermodynamic stability than the non-depositing sample's one at PH6.13 in Fusayama solution.

Fig. 1-10. The corrosion potential change plotted as a function of time of samples in Hank's solution (PH7.45)

Fig. 1-11. The Corrosion potential change plotted as a function of time of samples in Fusayama solution (PH6.13)

the deposited sample has a higher thermodynamic stability than the non-depositing

 treated untreated

 treated untreated

0 10 20 30 40 50 60

t/min

0 1 0 2 0 3 0 4 0 5 0 6 0

t / m i n

Fig. 1-11. The Corrosion potential change plotted as a function of time of samples in

Fig. 1-10. The corrosion potential change plotted as a function of time of samples in Hank's

sample's one at PH6.13 in Fusayama solution.






E/V(SCE)

Fusayama solution (PH6.13)



0.00

E/V(SCE)

solution (PH7.45)
