Biomedical Engineering Reference
In-Depth Information
but surface of the grains/pores is covered by anodic oxide, resulting
in corrosion current (curve d) almost of one order of magnitude
smaller, than for the unetched sample (Table 5.6) [15].
Figure 5.24
Corrosion polarization curves for Ti-6Al-4V: bulk
microcrystalline (a), bulk microcrystalline electrochemically
etched (b), nanocrystalline (c), nanocrystalline and electro-
chemically etched (d) [15].
Table 5.6
Corrosion current
I
c
and corrosion potential
E
c
for the Ti-
6Al-4V [15]
I
c
(A/cm
2
)
Sample
E
c
(V)
4.30 × 10
-8
Ti-6Al-4V — bulk microcrystalline not
etched
-0.66
1.82 × 10
-7
Ti-6Al-4V — bulk microcrystalline
electrochemically etched
-0.45
Ti-6Al-4V — nanocrystalline not etched 1.05 × 10
-5
-0.59
4.28 × 10
-6
Ti-6Al-4V — nanocrystalline
electrochemically etched
-0.36
Due to toxicity of V and Al, new alloys without these elements
are desirable, which provide properties accurate for hard tissue
implants. The new V-free Ti-35Nb-5Ta-7Zr alloy anodized in H
3
PO
4
+ NaF which results in nanotubes and nanoporous oxide formation
[40]. Saji
et al
. investigated theirs corrosion resistance (Fig. 5.25,
Table 5.7) [40].
