Characterization of Tinbcn Coatings Subject to Micro-Abrasion Wear and Corrosion Phenomena in a Simulated Biological Fluid

The materials used in the orthopedic surgery present changes in their characteristics due to the human body has an influence by means of the reactions among the implant and the tissue; caused by corrosive phenomena mainly where the material interacts with a  biological fluid, and wear processes owing to the fictional forces that must withstand. When corrosive and wear processes occur simultaneously, is produced an acceleration of both processes due to its synergy, which increases the risk that the patient presents health complications and / or catastrophic failure of the implant. [1-3] 

As a result, it was obained equipment that performs wear and corrosion test simultaneously, which has a sample holder coupled to a lever arm, that rotates on its pivot controlling the applied load on the sample when comes into contact with the abrasive ball. The ball is fixed among two coaxial supported on bearings, where one of them is driven by DC motor with an encoder with the purpose of ensuring the velocity and number of revolutions of the test. To simulated biological conditions, it was adapted a potentiostat which has an electrochemical cell composed by: the reference electrode -RE (Ag/AgCl), the auxiliary electrode-AE (Platinum wire) and the sample-WE. The electrodes are immersed in Hank’s solution which acts as electrolyte and fluid simulated biological fluid. 

In the figure 2 is obtained the Tafel polarization curves in function of the bilayer number [TiCN / TiNbCN]n. The curves are strongly dependent on the number of bilayers, which indicates the influence of the interfaces present in a multilayer. The films show higher electrochemical potential in comparison with the substrate without coating which confirms the protective effect of the coatings. This behavior is characteristic of the multilayer structures; in consequence of the increase of the bilayer number, the number of pores, the density and the number of interfaces also increases for all the thickness of the system. It leads to the required energy to move the Cl- ions through the interface of coating/substrate with liberty is higher, therefore the ions that get to the substrate are less due to the direction change which experience the Cl- ions when they find a new interface. 

In general, the tests allowed to determine the decrease in mass loss of the material as a consequence of the synergistic effect of the micro-abrasion wear and the corrosion in a simulated a biological environment. Additionally, it was observed a protection due to the protector layer generated by the interaction among the coating and the simulated biological fluid.

 References

 [1] J.B. Park, Biomaterials Science and Engineering. New York: Plenum Press. 1984. Pp. 213-185.

 [2] J.Breme, R. Thull and C.J.Kirkpatrick. Metallic Bio-material Interfaces. Weinheim: Wiley-VCH, 2007.

 [3] S. Fukazaki. H. Urano and K. Nagata. Adsorption of Protein Onto Stainless-Steel Surfaces, Journal of Fermentation and Bioengineering, vol1, pp. 6–11, 1995.