Abstract
Base-metal alloys of the nickel-chromium system are widely applied in fixed prosthodontics. The principal purpose of the addition of beryllium is to increase the fluidity of the Ni-Cr alloy during melting and increase the castability. In this study the effects of beryllium addition, by weight percentages of 0.5, 1.0 and 2.0, respectively, on the microstructure and corrosion resistance of seven Ni-Cr-based and NP2-based dental alloys were examined in Ringer's solution at 37°C. The experimental results indicate that addition of beryllium has a very significant effect on lowering the pitting potentials, open-circuit potentials, passive-film resistances and, on the contrary, increasing the passive-film capacitances. The presence of beryllium greatly reduces the thickness of the passive film and makes the corrosion resistance worse. This effect is more pronounced for NP2-based dental alloys. Examination of the corroded surfaces reveals that it is the Ni-Be eutectic phase being preferentially attacked.
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