The effect of chemical passivation on the ion release in a commercial cobalt-chromium alloy

Abstract

Introduction and goal: Base cobalt-chromium alloys have important applications in manufacturing of dental prostheses. One of the properties required to determine their function is corrosion resistance and ion solubility. In this research, the effect of chemical embedding on ionic dissolution of Flexicast cobalt-chromium alloy has been investigated. Method: Twenty samples of Flexicast alloy were prepared. Ionic dissolution of cobalt-chromium alloy was investigated in two groups of embedded and non-embedded groups. 10 samples were immersed in Na2SO4 × 10H2O (PH = 7) + graphite solution at 20 ° C for 24 hours. 10 others samples were not embedded. The ion solubility was measured weekly by atomic absorption spectrometry for 4 weeks. The surface morphology of the specimens was examined by SEM scanning electron microscopy. Corrosion rate was measured by Kruskal-Wallis test at 4 different times and the Mann Whitney test was used to compare the two groups. P value less than 0.05 was considered statistically significant. Results: Embedding the alloy significantly reduced cobalt ion solubility in the first and fourth weeks, and chromium in the first, second and fourth weeks, but the rate of cobalt ion solubility in the second and third weeks, and chromium in the third week were the same in the embedded and non-embedded (p> 0.05). Kruskal Wallis test was used to compare the corrosion rate at 4 different times and the Mann Whitney test was used to compare the two groups. Significance level was considered p <0.05. Conclusion: The rate of ionic dissolution in the embedded group was not significantly lower than that in the non-embedded group. SEM images showed higher porosity and corrosion in the non-embedded group.