Corrosion behavior of structural phases in high copper dental amalgam

The effects of crevice corrosion on the major structural phases of a high copper dental amalgam were studied in vitro. Three kinds of samples were used: (1) amalgam prepared from a high copper, single composition alloy, (2) annealed ingots of the Ag3Sn and Cu3Sn phases, and (3) high copper, single composition alloy tablets electroplated with mercury. Specimens were examined in a scanning electron microscope before and after the exposure to a corrosion environment. The Ag3Sn and Cu3Sn phases were least affected by corrosion. The Ag-Hg-Sn phase (gamma1) slowly deteriorated, but the attack was nonuniform. The Cu6Sn5 phase exhibited good corrosion resistance, better than that of gamma1 phase. Particles of a tin rich phase of uncertain origin were observed on some of the samples after long exposures.