Electrochemical corrosion kinetics of tin and tin amalgams in NaCl aqueous solutions |
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Authors: | François Rouelle Florence Toumelin-Chemla |
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Institution: | (1) Laboratoire d'Electrochimie, LI2C Boite 51, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05, France,;(2) Département des Biomatériaux, Faculté d'Odontologie, Université Paris V, 1 Rue Maurice Arnoux, 92120 Montrouge, France, |
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Abstract: | Electrochemical techniques were used to determine the corrosion rate of pure tin metal as compared to 80 Sn/20 Hg tin amalgam.
X-ray diagrams showed that this amalgam was a crystalline γ2 phase, whereas a 50 Sn/50 Hg amalgam contained liquid alloy embedded in the same γ2 phase. Open circuit potential measurements, combined with narrow range potential scanning voltammetry, lead to the conclusion
that amalgamation resulted in enhancement of the corrosion current, mainly by increasing the cathodic electron transfer reaction
kinetics both in deaerated and in oxygen-saturated NaCl solution. When maintained at zero current potential in a solution
containing dissolved O2 gas, the samples were gradually covered with an insulating oxide layer which was identified by a series of electrochemical
impedance diagrams recorded at different time intervals. The oxide layer was firmly adherent to the bulk tin metal but was
poor at protecting the amalgam electrode. Finally, at potential values where the anodic current reached a few mA/cm2, the pure tin metal surface was suddenly deteriorated by the formation of extremely deep pinhole corrosion pits, while this
effect was smoothed down by amalgamation.
Electronic Publication |
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Keywords: | Electrochemical corrosion Tin Amalgams Impedance |
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