Study on the corrosion resistance of Cr ahoy in the artificial saliva with different pH value / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the effect on the corrosion resistance of Cr alloy in the artificial saliva with different pH value in vitro.</p><p><b>METHODS</b>Compared to Ti alloy, electrochemical technique was used to measure the electric potential of corrosion (E(corr)), current density of corrosion (I(corr)) Cr alloy in the artificial saliva with different pH value. The corrosion and corrosion resistance mechanism on Cr alloy in the artificial saliva with different pH value had been investigated by the EIS curves.</p><p><b>RESULTS</b>The corrosion resistance of Co-Cr alloy was better than Ti alloy. The value of I(corr) was lower and the value of R(p) was larger than Ti alloy. The corrosion resistance of Ni-Cr alloy was worse than Ti alloy. The value of I(corr) was larger and the value of R(p) was lower than Ti alloy. The pH value in the artificial saliva was decreased, the I(corr) value of three types of alloy increased, the R(p) value of three types of alloy decreased. But the changes of Co-Cr alloy was smaller than that of Ti alloy or Ni-Cr alloy.</p><p><b>CONCLUSION</b>The corrosion resistance of Co-Cr alloy was superior to that of Ni-Cr alloy and Ti alloy. In the acid artificial saliva, the corrosion resistance of three types of alloy descended evidently.</p>

Influence of different NaCl concentration on passive behavior of Cr alloy in vitro / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the properties of passive film of three Cr alloys and to analyze their corrosion resistance in the artificial saliva with different NaCl mass fraction in vitro.</p><p><b>METHODS</b>Artificial saliva with 1%, 2% and 3% NaCl mass fraction was prepared. Cobalt-chromium alloy, nickel-chromium alloy and Ti-Ni-Cr alloy were employed as the working electrode in the artificial saliva. Semi-conductor properties of passive film on Cr alloy was analyzed by Mott-Schottky plots. In addition, the factors which affect the semi-conductive compact characteristic of the passive film was also discussed.</p><p><b>RESULTS</b>The passive film exhibits n-type semi-conductive characters. With the increasing of NaCl mass fraction, the carrier density of the Cr alloys also increased. The carrier density of the cobalt-chromium alloy, nickel-chromium alloy and Ti-Ni-Cr alloy are 3.71 x 10⁸, 2.34 x 10⁹, and 7.66 x 10⁹/cm³ respectively. This decreases its donor density and its film stability.</p><p><b>CONCLUSIONS</b>When exposed to saliva environment with high concentration of chlorine ion, corrosion resistance of the three types of Cr alloys decrease. This will reduce the service life of Cr alloy prosthesis.</p>