Method: Four test solutions were prepared for immersion of electrodes: 154 mM (0.9%) NaCl (pH=5.5), 48 mM (0.2%) NaF + 154 mM (0.9%) NaCl (pH=5.0 by addition of lactic acid), 150 mM H2O2 + 154 mM (0.9%) NaCl (pH=4 by addition of lactic acid), and 150 mM H2O2 + 154 mM (0.9%) NaCl (pH=8 by addition of sodium hydroxide solution).
Quartz crystal oscillators (9 MHz) deposited with titanium or titanium-chromium (Ti-10 mass %Cr) alloy were used as working electrodes.EQCM reflects variations in oscillation frequency of electrodes. These frequency variations are linked to mass variations at the electrode surface. Simultaneous recording of frequency of electrode and electrochemical measurements in each solution were performed by a single computer. Following data acquisition, EQCM data were analyzed to determine the corrosion reaction.
Result: In the NaCl solution, the electrode frequencies of titanium and titanium-chromium alloy showed no remarkable change. The titanium electrode showed a gradual increase in frequency in the acidulated fluoride-containing solution and alkaline H2O2-containing solution, indicating a loss of mass by dissolution, whereas the titanium-chromium alloy electrode showed little change in frequency in both solutions, indicating suppression of dissolution.
Conclusion: The results confirm that corrosion of titanium takes place in acidulated fluoride- or alkaline peroxide-containing solution, and that addition of chromium suppresses corrosion of titanium alloys. This study was supported by a Grant-in-Aid from the JSPS.