Development of the protecting method for hydrogen(and its isotopes) permeation through metallic pipes by cathodic polarization

用库仑滴定法测定了氢在Fe-Cr-Al耐热合金（Cr22%，Al5%，Fe63%，通常称为“Kanthal合金”）管材中的渗透。即使不进行任何预处理，测得的磁导率系数也仅为常用耐热Fe-Cr合金的千分之一。测量值与具有与在金属管上形成的氧化物层相容的厚度的氧化铝陶瓷的测量值几乎相等，这表明氢在Fe-Cr-Al合金管中的渗透是由在管表面形成的氧化铝层控制的。研究了铝管及其极化效应，以探讨阴极保护氢渗透的可能性。通过电动势测量，证实了由于化学极化效应，合金基体中的氢电势保持在高值， ...更多信息 已经被我们指出了。然而，阴极极化对氢渗透的影响没有得到明确的证实，因为在还原条件下，氧化膜由于极化而变得不稳定，而且渗透速率自然处于非常低的值。为此，采用多晶氧化铝陶瓷管代替金属管表面的氧化膜，并在管的内外两侧分别设置多孔铂电极，详细研究了极化对该样品的影响，证实了随着极化条件的改变，氢从氧化铝本体中引入或释放。通过计算极化试样中氢的化学势分布，对这一现象进行了分析。基于该分析，确定了氢在商业多晶氧化铝中的溶解度。在1573 K下施加0.8V的阴极极化一段时间后，观察到通过氧化铝管的渗透被完全阻断。因此，在金属管表面形成稳定的二价氧化铝膜，证实了对金属管的氢渗透进行阴极保护的可能性，并对金属氧化初期的异常掺氢、氢在氧化铝中的过饱和、并观察到与氢/质子电极反应有关的新机理。本研究的子工作也给出了这些现象的可能解释。少

The permeation of hydrogen through the pipe made of Fe-Cr-Al heat-resisting alloy (Cr22%, Al5%, Fe63% usually called "Kanthal Alloy") was measured by coulometric titration method. Even without any pretreatments, the measured permeability coefficient was found about one thousandth of that of usual heat-resisting Fe-Cr alloy. The measured value was nearly equal with that of alumina ceramics of the compatible thickness with the oxide layer formed on the metallic pipe, which suggests that the hydrogen permeation through the Fe-Cr-Al alloy pipe is controlled by the alumina layer formed on the surface of the pipe.The electromotive force established across the oxide film formed on the surface of the Fe-Cr-Al pipe and its polarization effect were studied in order to examine the possibility of cathodic protection of the hydrogen permeation. By emf measurement the hydrogen potential in the alloy substrate was confirmed to be maintained at high value due to the chemical polarization effect which … More had been already pointed out by us. The effect of cathodic polarization on the hydrogen permeation, however, was not confirmed clearly because the oxide film was made unstable by polarization in the reducing condition and also the permeation rate was naturally at very low value. Therefore, the pipe of polycrystalline alumina ceramics with porous platinum electrodes on inner and outer sides were employed in the place of the oxide film formed on the surface of the metallic pipe and the effect of polarization on this sample was studied in detail.It was confirmed that hydrogen was incorporated or released from the bulk of alumina on the change of the polarization conditions. This phenomenon was analyzed by calculating the hydrogen chemical potential profile in the polarized specimen. Based on this analysis, the solubility of hydrogen into the commercial polycrystalline alumina was determined. After a period of cathodic polarization by imposing 0.8V at 1573 K, it was observed that the permeation through the alumina pipe was perfectly blocked. Therefore, the possibility of cathodic protection of hydrogen permeation of a metallic pipe was confirmed if the stable alumina film doped with bivalent elements was formed on the surface of the pipe.The new phenomena such as the extraordinary incorporation of hydrogen at initial stage of oxidation of the metal, the super saturation of hydrogen into alumina, and the new mechanism relating with the hydrogen/proton electrode reaction were observed in the course of this study. The possible explanations of these phenomena were also given in the sub works of this research. Less