To facilitate work and to enable accurate measurement by integrating an opposed electrode applying AC voltage, a collation electrode detecting a voltage value of AC voltage and an insulating part electrically insulating both electrodes in a rod shape.
A measuring electrode 20 is constituted of a support part 21 becoming a support, an opposed electrode 23, a collation electrode 24, an insulating part 22 insulating both electrodes and a ceramic plate 25 for the continuity with soil. The support part 21 is constituted of a material quality having strength to some degree such as steel and the opposed electrode 23 and the collation electrode 24 are constituted of a conductor such as steel and the insulating part 22 is constituted of insulating matter such as a resin. A measuring electrode 20 is thrust in a steel pipe in soil to apply definite AC voltage across the opposed electrode 23 and the collation electrode 24 and the impedance between the steel pipe and the opposed electrode 23 is calculated from the voltage applied to the collation electrode 24 and the current flowing through the opposed electrode 23 and the corrosion of the steel pipe is diagnosed from the impedance. Since the opposed electrode 23 and the collation electrode 24 are integrally constituted, a small hole may be bored in a paved surface and work becomes easy and, since both electrodes are held to definite positional relation, impedance can be accurately measured.
SHIBATA MUTSUMI
SATO SAKAE
