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Electrochemistry of the saline corrosion of conventional dental amalgams
Author(s) -
SARKAR N. K.,
GREENER E. H.
Publication year - 1975
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/j.1365-2842.1975.tb00910.x
Subject(s) - corrosion , polarization (electrochemistry) , amalgam (chemistry) , electrochemistry , materials science , dissolution , hydroxide , passivity , tin oxide , oxide , tin , metallurgy , electrode , inorganic chemistry , chemistry , electrical engineering , engineering
Summary The electrochemical behaviour of the component phases of dental amalgam, viz. Ag 3 Sn (γ), Ag 2 Hg 3 (γ1), Sn 7–8 Hg (γ2), Cu 3 Sn, Cu 6 Sn 5 and a composite of γ1 +γ2 phases were evaluated in saline solution by standard anodic polarization techniques. Using multi‐electrode theory a theoretical polarization diagram was constructed from the composite phases and compared with an anodic polarization profile attained from conventional dental amalgam. A strong agreement was obtained. From analysis of the electrochemical reactions it was found that the passivity of γ2 is due to the formation of stannous and/or stannic oxide (hydroxide) and that the corrosion failure of dental amalgam occurs through the dissolution of this passive oxide in γ2 at potentials of −250 mV Vs. SCE with the formation of tin oxychloride. The corrosion behaviour of Cu 6 Sn 5 is similar to that of γ2 phase and its presence impairs the corrosion resistance of dental amalgam. If the copper containing phase is Cu 3 Sn, it will be passive in Ringer's solution, possibly as a result of Tamman's ‘multiple rule of eight’.