PURPOSE: To make sensing of limits for serviceability of lining possible and to make detection of corrosion in the lining easy by a method wherein nonconductive resin layers and a conductive resin layer are layered in combination, a plurality of detecting terminals are installed to the conductive resin layer so that the terminals penetrate the nonconductive resin layer provided to the wall side of the tank main body and an electric circuit is formed between the detecting terminals and an electrode provided in the tank.

CONSTITUTION: Interior surface of a wall 1 of a tank main body is lined with a layered lining formed of a nonconductive resin layer 2, a conductive resin layer 3 and a nonconductive resin layer 4 that are layered in the above-mentioned order. A plurality of detecting terminals 5 for detection of corrosion in the nonconductive layer 4 that is liable to occur by effect of liquor in the tank are installed in scattering to the face of the conductive resin layer 3 so that the terminals penetrate the nonconductive resin layer 2. Each one end of each of the detecting terminals 5 is fixed to each one of specified positions in the conductive resin layer 3 and each of the other ends is guided to the outside of the tank through through holes bored to the nonconductive resin layer 2 and the wall 1 of the tank main body, and is connected to a shifting switch 6 through each one of lead wires 10, and thereby an electric circuit is formed with an electrode 7 provided in the tank and an electric power source 9 connected, and a measuring instrument 8 is provided for measurement of electric characteristics including electric resistance values, electric current values, etc.