ELECTROCHEMICAL DETERMINATION OF THE CORROSION-RESISTANCE OF NOBLE DENTAL CASTING ALLOYS

Forty-four dental casting alloys and pure metals have been evaluated f or corrosion resistance in an artificial saliva. The electrochemical t ests included measurement of the rest potential and tracing of polariz ation curves. Qualitative comparisons of the normalized polarization c urves, and quantitative determination of corrosion resistance, a nd of corrosion and breakdown potentials, provided complementary means of e valuation. Alloys were assigned two families: alloys for crowns and br idges (C&B alloys), and alloys for ceramic veneering (PFM alloys). Amo ng these two families, groups were based on the gold-content (high and low), and on the main non-gold component: silver for C&B alloys, and palladium for PFM alloys. Pure metals and some non-noble alloys have b een included as references. From this study, it clearly appears that t he PFM alloys, having a higher content of noble metals, are more corro sion resistant than the C&B alloys containing copper and silver. Some relationships between noble-metal content and electrochemical paramete rs such as rest potential and corrosion resistance, have been identifi ed, but the strength of the correlations is somewhat lowered by the in fluence of additional parameters, such as the presence of non-noble co mponents or the nature of the microstructure. The present investigatio n is part of a larger study including other electrochemical parameters as well as various biocompatiblity tests on the same set of 44 alloys .