Novel sensor to investigate microstructural contributions to corrosion of high‐palladium dental alloys

Abstract

There is incomplete understanding of corrosion mechanisms for high‐palladium dental alloys used for metal‐ceramic restorations. This investigation employed two complementary techniques as a novel sensor for an initial investigation of corrosion tendencies for phases in representative high‐Pd alloys with Pd–Cu–Ga and Pd–Ga compositions. After the initial oxidation step and simulated porcelain‐firing cycles, specimens were polished for examination by Scanning Kelvin Probe Force Microscopy and Atomic Force Microscopy to evaluate the Volta potential difference across the surfaces and correlate potential differences with microstructural phases. The Ru‐rich phase, present in high‐Pd alloys from use of Ru as a grain‐refining element, was clearly more noble than the Pd solid solution matrix in the Pd–Cu–Ga alloys but had much less Volta potential difference than the matrix in the Pd–Ga alloy. Other precipitates in the alloy microstructures had minimal observable differences in Volta potential compared to the matrix. While high‐Pd alloys have been found previously to show excellent overall in vitro corrosion resistance, the Ru‐rich phase may cause localized galvanic corrosion in Pd–Cu–Ga alloys leading to potentially problematic Pd ion release, but have less effect on corrosion in Pd–Ga alloys.

Electrochemical impedance spectroscopy study of corrosion characteristics of palladium–silver dental alloys

“…Another study of high‐palladium alloys, 35 using a combined scanning Kelvin probe/atomic force microscopy technique, 36‐39 has shown that the ruthenium‐rich particles in the microstructures (arising from the use of ruthenium as a grain‐refining element), have higher Volta potential than the palladium solid solution matrix. These particles may thus act as locus points for the corrosion of the solid solution matrix with the release of Pd ions.…”