Corrosion Behavior of a Nickel-Base Dental Casting Alloy in Artificial Saliva Studied by Weight Loss and Polarization Techniques

OBJECTIVES: Nickel-chromium (Ni-Cr) base dental alloys with desirable properties have been employed in prosthodontics for years. Corrosion behavior of a Ni-Cr base alloy in artificial saliva with different pH values is determined in this work. MATERIALS AND METHODS: Corrosion behavior of Ni-Cr alloy was studied in artificial saliva with different pHs (2.5, 5, 7, and 9), using weight loss described by corrosion rate (CR) in mils per year (mpy) and potentiodynamic polarization described by corrosion potential (CP) in mV and current density (CD) in mA/cm(2). Surface morphology was assessed using scanning electron microscopy (SEM). Statistical difference was determined using one-way ANOVA and post-hoc Tukey’s honestly significant difference test with a difference significance of 95%. RESULTS: In the weight loss method, CR was 71.95±3.40, 17.26±1.03, 8.92±0.35, and 6.93±0.54 mpy at pH values of 2.5, 5, 7, and 9, respectively. Significant differences in CR were observed only at pH=2.5, while in CD, they were found at PH=2.5 and 5 (P<0.05). In the polarization method, CP values were significantly different. SEM exhibited the formation of preferential sites of corrosion attacks influenced by pH. CONCLUSION: Both techniques revealed consistent results. Corrosion resistance increases as pH increases towards less acidic conditions. In more acidic saliva, the corrosion rate is greater. The less acidic saliva leads to formation of a more stable passive film on Ni, and the dissolution of Ni decreases, leading to lower CRs.