Corrosion performance and electrochemical stability of 316L in body fluid
Faiza Kakaa*1, N.azzouz1, N.Boukmouch1, L.Bouchama1
1Laboratory of the Interactions Materials-Environment (LIME) Materials and Alloys Industry IC-WNDT-MI’16
Jijel, Algeria [email protected]
Abstract— Metal implants are the best choice for the long-term replacement of hard tissue, such as hip and knee joints, because of their excellent mechanical properties. 316L stainless steel is widely accepted as biocompatible metal implants.
The aim of this work is to study the biocompatibility of 316L stainless steel, for the manufacture of screw plates having high chromium and low carbon contents; in a simulated blood medium (Ringer’s solution). The specimen having a cylindrical shape, has been characterized by a spectral analysis for the identification of the chemical composition, a mechanical characterization (hardness Rockwell), physicochemical (X-ray diffraction), and finally electrochemical measurements (monitoring the free potential evolution, plots of polarization curves and electrochemical impedance spectroscopy (EIS) measurements were conducted after 4h, 6h, 24h, 48h, 168h, 215h, 10 days and 15 days of immersion in Ringer's solution. The influence of parameters such as electrolytic medium, pH, agitation of the medical device (screw plates used in orthopedics) has studied. Very low current densities were obtained, indicating the formation of a passive layer. Impedance spectra, represented in the Nyquist plan, exhibited a single constant system suggesting the formation of one layer.
Keywords— Implants; stainless steel; biocompatibility;
Ringer’s solution; X-ray diffraction.
I. INTRODUCTION
Stainles stel high resistance to corosion derives from a dense film of chromium oxide (pasive film) that naturaly forms on the iron surface. Generaly first requirement of any material serving in biological system is that it should be inert and not causing any undesirable reaction with its surounding. When stainles stel is placed inside a tisue, the interaction betwen the implant and tisue determines the degre of biocompatibilty. It implies to the abilty of the material to perform efectively with an apropriate host response for the desired aplications.(1) Common medical devices include hip replacements, prosthetic heart valves, neurological prostheses and drug delivery systems. (2)
Corosion as an electrochemical proces commences on the surface of stainles stel implants and subsequently affects the body response. This is undesirably folowed by release of ions such as chromium and nickel in surounding tissue which can negatively afect the response of host body to biomaterial. The literature has proven that nature concentration of ions Cr+3, Fe+2, Ni+1 inside the body may severely prevent the tisue functionality and can ultimately lead to severe health related consequences , therefore corosion of material is the first isue to be considered when the material is designed as a bio implant. It is also necesary to establish an understanding of biological factors efecting corosion. There are various in vivo and in vitro studies on corosion of metal implants which employed simulated body fluids. (3)
II. EXPERIMENTAL
The corrosion behavior of orthopedic implant stainless steel 316L has been studied in a simulated body fluid (Ringer's solution), using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques.
Polarization experiments were conducted after 4h, 6h, 24h, 48h, 168h, 215h, 10 days and 15 days, of immersion in Ringer's solution.
A stainless steel 316L sample of the following chemical composition (as percentage) was served as working electrode:
TABLE I. CHEMICAL COMPOSITION OF STAINLESS STEEL 316L.
C Mn Si Ni Cr Cu Mo V Ti Al
0.02 1.56 0.71 14.15 17.02 0.12 3.19 0.092 0.049 0.14
W Sn Co B Ta Mg Nb
0,25 0,023 0,037 0,009 0,041 0,021 0. 15
The working electrode was polished with different grades of SiC papers (500, 600, 800, 1200, 2000) and a finishing with diamond paste of 1 µm to obtain a mirror surface, degreased with acetone and rinsed with distilled water, before its
immersion in a simulated blood medium (Ringer’s solution).
Potentiostatic polarization studies were carried out using Potentiostat/Galvanostat PGZ-301.
TABLE II. CHEMICAL COMPOSITION OF RINGER'S SOLUTION.
Composition Concentrations (g/L) Concentrations (mole/L)
NaCl 2.25 0.0384
KCl 0.105 0.0014
CaCl2 0.12 0.0010
NaHCO3 0.05 0.0005
H2O Graduated flasks 1000 ml Graduated flasks 1000 ml
III. RESULTS AND DISCUSSION A. Absence of agitation
-500 -400 -300 -200 -100 0 100 200 300 400 -10
-9 -8 -7 -6 -5 -4
Logarithmic
logi(µA/cm2)
E(mV/ECS)
Without agitation
Fig. 1. Polarization curves obtained for the stainless steel 316 L immersed in Ringer’s solution without agitation (T=37C°) .
B. Presence of agitation
-500 -400 -300 -200 -100 0 100 200 300 400 -10
-9 -8 -7 -6 -5 -4
Logarithmic
logi(µA/cm2)
E(mV/ECS)
With agitation
Fig. 2. Polarization curves obtained for the stainless steel 316 L immersed in Ringer’s solution with agitation (T=37C°).
TABLE III. ELECTROCHEMICAL PARAMETERS OF STAINLESS STEEL 316L
IN RINGER’S SOLUTION IN THE ABSENCE AND PRESENCE OF AGITATION.
Ecorr
(mV/SCE)
icorr
(µA.cm-2)
Vcorr
(mm.an-1)
RP
(K.cm2) Without
agitation - 43.9 0.5693 6,658 .10-3 170.79 With
agitation 15.5 0.0974 1,139 .10-3 310.59 In this work we followed the agitation action of orthopedic implant of stainless steel 316L in Ringer’s solution (physiological solution blood simulated) at T=37°C.
According to polarization curves (Figure 1 and figure 2) we can be said that:
Stainless steel 316L in presence of agitation has a noble potential than unagitated solution and the polarization resistance of SS 316L in presence of agitation is twofold the resistance in solution of agitation.
C. Impedance characteristics stainless steel 316L
Fig.1. Impedance spectroscopy analysis of 316L stainless steel in Ringer's solution for various immersion times at 37 ° C.
The existence of two capacitive arcs:
The first capacitive arc (high -frequencies) correspond to transfer of charge metal / solution interface.
The second capacitive arc (low- frequencies) corresponds to the formation and growth of oxide and hydroxide film.
TABLE IV. The equivalent circuit parameter obtened by adjusting electrochmical of impedance data for stainless steel 316L in Ringer's solution for various immersion times with a total error ˂4%.
0 100 200 300 400 500 600 700 800 900 1000
0 100 200 300 400 500 600 700 800 900 1000
-Zi [kohm.cm²]
Zr [kohm.cm²]
4h 6h 24h 48h 168h 215h 10 days 15 days
At the beginning of immersion the resistance transfer of charge is increased within 4h, 6h, 24h, 48h while the capacitance values of Qdc decreased slightly during the immersion time, due to construction of passive layer enriched with chrome; after 48 hours of immersion, Rtc is decreased
indicating deterioration of the passive layer.
CONCLUSION
Stainless steel surgical quality (316L stainless steel) is one of the materials that are widely used as implants in orthopedic surgery. The aim of this work is to study the biocompatibility of 316L stainless steel, for the manufacture of screw plates having high chromium and low carbon contents, in a simulated blood medium.
The electrochemical study reveals the best corrosion resistance of 316L stainless steel in Ringer's solution.
REFERENCES
[1] Yang Leng,Donglu Shi,”Introduction to biomaterials”
Tinsinghua University Pres, 206,pg 601-637.
[2] U Kamachi Mudali, T M Sridhar and Baldev Raj,
“Corosion of bioplants”, Sadhana Vol.28, Parts 3and 4, June/August 203, Pg 601-637.
[3] Omanonic S,Roscoe SG.”Electrochemical studies of the absorbtion behavior of bovine serum albumin on stainless steel”, Langmuir 199;15(23); pg 8315-21.
CPE1 CPE2
Temps d’imm -ersion
Re
(Ωcm2) Qdc
(Ω1Snc m-2)
1 Rtc
(Ωcm2) Qf
(Ω1Sncm2)
2 Rf
(Ωcm2)
4 heures
139,4 1,32 .10-5
0,785 15,14 .105
0,96 . 10-5
0,58 0,827 .104 6
heures
136,3 1,12 .10-5
0,787 19,37 .105
0,92 .10-5
0,58 0,939 .104 24
heures
123,9 0,53 .10-5
0,806 39,89 .105
1,04 . 10-5
0,56 1,828 .104 48
heures
100,2 0,78 .10-5
0,722 56,33 .105
0,95 . 10-5
0,57 1,586 .104 168
heures
58,64 1,35 .10-5
0,655 2,996 .105
1,45 . 10-5
0,58 2,864.
104 215
heures
44,81 1,56 .10-5
0,685 1,984 .105
1,66 . 10-5
0,58 5,842 .104 10
jours
43,59 2,02 .10-5
0 ,658 1,784 .105
1,60 . 10-5
0,60 5,979 .104 15
jours
30,75 3,62 .10-5
0,674 1,643 .105
1,89 . 10-5
0,63 47,7 .104
