| 1162 Mechanism of PdAgCu Alloys Interaction with Model Saliva | ||
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L. JOSKA, M. PODDANA, and J. LEITNER, Institute of Chemical Technology Prague, Prague 6, Czech Republic Objectives: The ternary system PdAgCu is the basis of many dental alloys. Corrosion resistance of these materials is high. Important is character of the originating corrosion products, which may trigger an adverse reaction of human body. The aim of this study was to determine the mechanism of corrosion interaction between PdAgCu alloys and model saliva. Methods: Measurements were made with four PdxAg90-xCu10 alloys and pure metals. The exposure environment was model saliva solution consisting of KCl, NaHCO3, NaH2PO4, KSCN and lactic acid (pH=6,8; temperature 37oC). The potentiodynamic curves and time dependences of the open-circuit potential were measured, PTFE multiple crevice washer was used to simulate the influence of crevices. Potential-pH diagram for the system Pd60Ag30Cu10-model saliva was calculated for an extensive set of possible corrosion products. XPS measurements of exposed and non-exposed samples were carried out. Results: The course of potentiodynamic curves of all studied alloys was approximately identical in the region of expectable potentials in vivo. The open-circuit potentials ranged in a narrow band from 0,26 to 0,3V/SHE. These values significantly differ from Eocp of both silver and palladium. According to the results of the equilibrium calculation, CuSCN, Cu2O and CuO are the only originating solid substances up to the potential of 0,3V/SHE. The asymmetrical copper XPS peak corresponding to the presence of Cu2O/CuO was noted in the spectra. These results indicate the presence and complex character of the surface layer. As a consequence, based on the results of electrochemical measurements, the studied alloys were susceptible to crevice corrosion. Conclusion: The alloying of the palladium-silver system with copper strongly influences the corrosion behaviour of the alloys. Electrochemical reactions of copper lead to the formation of a passive layer. This fact brings about the susceptibility to nonuniform corrosion. Supported by MSM 6046137302 and 1H-PK14 (surface analysis) projects. | ||
| Seq #100 - Dental Materials VII 3 3:30 PM-4:30 PM, Thursday, 29 June 2006 Brisbane Convention & Exhibition Centre Exhibit Hall 1 | ||
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