Biomedical Engineering Reference
In-Depth Information
Corrosion tests of Ni-free stainless steels with nanostructure
were performed in H
2
SO
4
and Ringer's solution. In H
2
SO
4
the
corrosion current,
I
corr
, in the case of Fe
59
Cr
23
Mn
12
Mo
6
N is
1.3 × 10
-5
A/cm
2
. The corresponding values of Fe
54
Cr
24
Mn
21
Mo
1
N
and Fe
64
Cr
24
Mn
10
Mo
2
N are 1.6 × 10
-4
and 5.1 × 10
-4
A/cm
2
,
respectively.
I
corr
values indicate that addition of Mo and reduction
of Mn resulted in appreciable decrease in the corrosion current
density — two orders of magnitudes and corrosion rate. Measured
values are considerably improved compared to widely used in
medicine 316L stainless steel.
In Ringer's solution tests, the corrosion current,
I
corr
, in the
case of Fe
59
Cr
23
Mn
12
Mo
6
N is 2.6 × 10
-5
A/cm
2
. The corresponding
values for Fe
54
Cr
24
Mn
21
Mo
1
N and Fe
64
Cr
24
Mn
10
Mo
2
N are 6.9 ×
10
-6
, and 4.9 × 10
-6
A/cm
2
, respectively. Calculated corrosion rates
for Fe
54
Cr
24
Mn
21
Mo
1
N and Fe
64
Cr
24
Mn
10
Mo
2
N steels, 0.073, and
0.052 mm/year, respectively, show that corrosion rate is four
times lower than in 316L stainless steel.
Table 6.4
Results of corrosion test in H
2
SO
4
and Ringer's solution [28]
0.1 M H
2
SO
4
Ringer's solution
Corrosion
rate
[mm/year]
I
corr
[A/cm
2
]
I
corr
[A/cm
2
]
Corrosion rate
[mm/year]
Sample
3.6 × 10
-3
1.0
9 × 10
-5
316L
0.30
Fe
54
Cr
24
Mn
21
Mo
1
N1.6×10
-4
1.2
6.9 × 10
-6
0.073
Fe
59
Cr
23
Mn
12
Mo
6
N1.3×10
-5
0.18
2.6 × 10
-5
0.27
Fe
64
Cr
24
Mn
10
Mo
2
N5.1×10
-4
2.1
4.9 × 10
-6
0.052
The comparison of results obtained for samples in H
2
SO
4
and
Ringer's solution (Table 6.4) show that synthesized stainless
steels manage much better in chloride ions environment. Chemical
composition of steels plays a bigger role in case of H
2
SO
4
, while in
Ringer's solution, differences are much smaller.
These results indicate that FeCrMnMoN stainless steels have
superior corrosion resistance in H
2
SO
4
and Ringer's solution
environments than the conventional metallic biomaterial, 316L.
The addition of nitrogen to a stainless steel inluences corrosion
