Abstract
Purpose: Little is known about the corrosion caused by contact with Ag-Pd-Cu-12Au alloys which are commonly used for cast crowns. The purpose of this study was to investigate the state of early corrosion behavior by contact with Au-Pd-Cu-Au alloys containing different amounts of Cu using X-ray photoelectron spectroscopy.
Materials and Methods: Three kinds of plate specimens of Ag-Pd-Cu-Au alloy containing different amounts of Cu were cast, and two specimens each were fixed and immersed into corrosion liquid for eight weeks. Then, the specimens were ultrasonically cleaned with acetone and ultra pure water and the corroded surface was analyzed using X-ray photoelectron spectroscopy. The depth that could be analyzed by XPS was about 10 nm, so the analytical results, it was the outermost surface and internal within 10 nm.
Results: Remarkable discoloration was observed on the edge of the contacted area on the specimen containing a larger amount of Cu. As early corrosion products, Ag2O, PdO, CuO, Cu2S and CuSO4 were observed and PdO was detected in the deeper part in many specimens with larger content of Cu. There was a higher ratio of CuSO4 in the specimen with a large content of Cu, and the ratio of CuO and Cu2S increased in the deeper part. The presence of Cu2S was detected from the surface to the inside of the specimen with a smaller content of Cu.
Conclusions: In the case of contact with Ag-Pd-Cu-Au alloys with different Cu amounts, Ag2O, PdO, CuO, Cu2S and CuSO4 were formed in early corrosion.
