Patent Number: 
Section: claims

1. An electrochemical corrosion potential sensor comprising:a conductive electrode fixing body;an electrode cap member made of zirconium and fixed to the electrode fixing body;a tubular insulator connected to the electrode fixing body;a tubular metallic housing connected to the tubular insulator; anda conductive wire passing through the tubular insulator and the tubular metallic housing and connected to the electrode fixing body;wherein in a first connecting portion of the electrode fixing body and one end portion of the tubular insulator, the electrode fixing body is disposed outside of the tubular insulator and overlapped to the tubular insulator;wherein in a second connecting portion of another end portion of the tubular insulator and the tubular metallic housing, the tubular metallic housing is disposed outside of the tubular insulator and overlapped to the tubular insulator;wherein the electrode cap member is disposed to cover an outer surface of the electrode fixing body;wherein the electrode cap member is disposed to cover the outer surface of the electrode fixing body and an outer surface of the first connecting portion; andwherein a metallic spacer made of zirconium is disposed in a clearance between the electrode cap member and the tubular insulator. 2. The electrochemical corrosion potential sensor according to claim 1, wherein the electrode cap member and the metallic spacer are fixed to each other by welding. 3. The electrochemical corrosion potential sensor according to claim 1, wherein an outer surface of the second connecting portion is covered with an interlayer; and a surface of the interlayer is covered with platinum. 4. The electrochemical corrosion potential sensor according to claim 3, wherein the interlayer is composed of titanium. 5. The electrochemical corrosion potential sensor according to claim 1, wherein a coefficient of linear expansion of each of the electrode fixing body and the tubular metallic housing is smaller than a coefficient of linear expansion of the tubular insulator. 6. The electrochemical corrosion potential sensor according to claim 5, wherein the electrode fixing body and the tubular metallic housing are made of Fe-29Ni-17Co alloy or Fe-42Ni alloy. 7. The electrochemical corrosion potential sensor according to claim 5, wherein the tubular insulator is sapphire or stabilized zirconia. 8. The electrochemical corrosion potential sensor according to claim 1, wherein a first metallization section is formed on an outer surface of the tubular insulator in the first connecting portion, and the first metallization section is connected with the electrode fixing body by metal. 9. The electrochemical corrosion potential sensor according to claim 1, wherein a second metallization section is formed on an outer surface of the tubular insulator in the second connecting portion, and the second metallization section is connected with the tubular metallic housing by metal.