Abstract: A sensor for monitoring a cooling liquid circulating in a circuit of a heat exchanger of an automobile, for example, includes a support for mounting the sensor on a pipe of the circuit so that the liquid is in contact with at least a part of the sensor, a corrodible membrane in contact with the liquid, and a visual indicator reacting to the degree of corrosion of the liquid. The visual indicator includes a piston movable under the combined effect of the breaking of the corrodible membrane and of the pressure difference between inside and outside of the pipe, at least one seal mounted on the movable piston, and the visual indicator protruding from the pipe and/or from the support when the membrane is corroded.

Abstract: In the present invention, Cr or Ta is used for gate terminals, aluminum or a metal mainly composed of aluminum is used for gate bus-lines extended therefrom, gate electrodes and thin film capacitances (additional capacitance, storage capacitance) and an anodic oxidized film composed of the metal and free from defect is used for at least one of gate insulators, dielectric films of the thin film capacitances and interlayer insulation films for the intersections between the bus-lines. In a more preferred structure, the anodic oxidized film is used for all of the gate insulators, the dielectric films for the thin film capacitances and the interlayer insulation films for the intersections between the bus lines. The present invention also relates to a method of selectively forming an anodic oxidized film on an aluminum pattern. That is, in a case of forming a selective oxidation mask to a desired region on the aluminum pattern with a positive type photoresist, in the present invention, an angle (.theta.