Journal of Dental Research, Vol 63, 926-931, Copyright © 1984 by International & American Associations for Dental Research Online Journals
Tarnishing and structures of some annealed dental low-gold alloys
H. Hero
Tarnishing of low-gold alloys in a Tuccillo-Nielsen test with 2% Na2S is
avoided when a single-phase structure is present as compared with
multi-phase structures, unless the Ag content of the single-phased alloys
is high. In all multi-phase structures, only the Ag-rich phase is attacked.
The possibility of annealing alloys to a single-phase structure decreases
with the reduction of Au content and with increasing amounts of Pd and Zn,
which tend to follow the Cu-rich phase. In static polarization testing of
single-phase materials in weak sulphide solutions, the Ag-rich alloys
display considerably higher anodic current densities (5-10 microA/cm2) than
do the Cu-rich low-gold and high-gold alloys (1 microA/cm2). No significant
differences between the alloys were observed with respect to cathodic
currents.
