アルミニウムとアルミニウム-亜鉛合金のカソード分極時の界面インピーダンス

抄録

The electrode impedance of pure aluminum and Al-Zn alloys have been measured at 10³Hz under potentiostatic-cathodic polarization. The cathodic current density for reduction of dissolved oxygen on pure aluminum is smaller than that on Al-Zn alloys, but hydrogen overvoltage for the former is larger than that of the latter. At potentials more noble than the hydrogen evolution potential, the oxygen reduction reaction seems to occur at local cathodes on the electrode and the ratio of the area of local cathodes to the whole surface of the electrode changes with time of polarization. At potentials less noble than the hydrogen evolution potential, the cathodic reduction of oxygen and hydrogen ion proceeds simultaneously and the dissolution of surface oxide films occurs together with the evolution of hydrogen. Under cathodic polarization, the surface of Al-Zn alloys appeared to be black but no significant color change occurs with the surface of pure aluminum. AES analysis showed that the black surface layer contains aluminum, zinc and oxygen with no detectable impurities such as iron and silicon.