Biomedical Engineering Reference
In-Depth Information
Fig. 5.7
Current density as
function of the potential
difference between the anodic
and cathodic branches of the
E-i curves for metals tested in
0.9%NaCl with a stable redox
system Fe(CN)
4
6
10
-3
stainless
steel
(316L)
10
-4
CoCrWNi - alloy
/Fe(CN)
3
6
.
Courtesy of Prof. J. Breme
(University of Saarbrucken)
10
-5
TiA
16
V
4
Ti
10
-6
Nb
Ta
10
-7
500
1000
1500
D
E
(
mV
)
Tabl e 5. 6
Illustration of the efficiency of corrosion protection by oxide films. Data collected
from [90, 212, 214]
Alloy
E
0
Breakdown
Polarization
Repassivation
resistance
a
potential
time (ms)
k.cm
b
V
V
0.5 V
C
0.5 V
Au
C
1.50
-
0.3
-
-
SS(316L)
-
C
0.2-0.3
4.4
72,000
35
CoCr
b
-
C0.42
-
44
36
CoNiCr
b
-
C0.42
3.3
36
41
Zr
b
-
C0.32
-
-
Zr-2.5Nb
c
C0.53
-
-
-
Ti-50Zr
c
-
C
0.93
-
-
-
Ti6Al4V
-
C
2.0
455
37
41
Ti-cp
-
C
2.4
714
43
44
Ta
0.96
C
2.25
1,430
41
40
Nb
1.13
C
2.5
455
48
43
a
Determination of polarization resistance see Fig. 3.6. Data from Breme [214]
b
CoCr: cast; CoNiCr: wrought
c
Pitting potential, data from Table II in [215]
with solvent extracts of the metal powders. Such extracts were made according to
an international standard procedure described in the ISO/EN10993-5 guidelines.
An amount of powder is extracted with
minimal essential medium
(MEM) supple-
mented with calf serum, glutamine and antibiotics. Following a strict time schedule,
the cell cultures are evaluated for confluency, degree of cellular lysis, change of
morphology and finally a cell count, all compared to a negative (UHMWPE) and
a positive cytotoxic control (latex rubber) [216, 217]. MEM is one of the media
simulating the body fluids but a more complex one compared to Hanks' (for more
