You\'re an engineer at Stryker, Inc. and your team\'s job is to redesign the fem

Question

You're an engineer at Stryker, Inc. and your team's job is to redesign the femoral component (shown below) of their total knee replacement system. The research and development department is interested in using a new combination of metal alloys for the base and fixating screws. One scientist proposes to use copper (Cu2+) for the base and cobalt (Co2+) for the screws. Another researcher suggests that there may be issues with corrosion. As an alternative, the second researcher proposes to use a combination of nickel (Ni2+) and Cobalt (Co2+) instead. Calculate the electrochemical potential for both metal combinations (assume standard conditions). SHOW ALL WORK! Based on the calculations above, which metal combination should the research group pursue? Provide brief explanation. A colleague suggests that the group should consider evaluating the corrosion potential under more relevant physiological conditions. The researchers assume that maximum dissolved concentration near the implant would be 86 meu g/dL and 202 meu g/dL for the OPTIMAL anodic and cathodic metal combination, respectively. Calculate the corrected electrochemical potential.

Explanation / Answer

Let's write the semi equation for the compounds:

1. Cu and Co:

Cu2+ + 2e- -------> Cu E°Cu = +0.34 V

Co -------- > Co2+ + 2e-   E°Co = +0.28 V

E° = 0.34 + 0.28 = 0.62 V

2. Ni and Co

Co -------- > Co2+ + 2e-   E°Co = +0.28 V

Ni2+ + 2e- ---------> Ni E°Ni = -0.25 V

E° = -0.25+0.28 = 0.03 V

b) Basing on the previous calculus, the group should be followinf the combination of Ni and Co, cause both of them has lowest E°, and the electrochemical potential will be very low, so corrosion (Which is a high state of oxydation) will not occur.

c) If concentration of both anodic and cathodic is that, then the corrected cell potential:

E = E° - 0.059/n logK

E = 0.03 - 0.059/2 log (86/202)

E = 0.0409 V

Hope this helps

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