Monitoring effects of a liquid on metallic installations

DETAILED DESCRIPTION What is claimed is: 1.
Process for monitoring the corrosive, erosive and/or encrusting nature of a liquid with respect to a metallic installation, comprising: immersing a metallic probe into the liquid whereby a double layer is created at the interface between the probe and the liquid; immersing an auxiliary electrode into the liquid near the probe so that the auxiliary electrode is electrically insulated from the probe and measuring the differential capacitance of the double layer and the electrical resistance between the probe and the auxiliary electrode, which are representative of the surface condition of the probe.
2.
Process as defined in claim 1 wherein said step of immersing is carried out by placing the probe near a surface of the installation, in contact with the liquid.
3.
Process as defined in claim 2 wherein the probe is made of the same material as the installation.
4.
Process as defined in claim 2 wherein the probe has substantially the same surface condition as the surface of the installation near which it is placed.
5.
Process as defined in claim 2 wherein the probe is an element of the surface of the installation near which it is placed.
6.
Process as defined in claim 5 wherein the probe is a removable element of the surface of the installation near which it is placed.
7.
Process as defined in claim 1 wherein the installation is a pipeline for the liquid.
8.
Process as defined in claim 1 wherein the installation is a heat exchanger.
9.
Process as defined in claim 8 wherein the installation includes an evaporator for the liquid.
10.
Process as defined in claim 1 wherein the liquid is water.
11.
Process as defined in claim 1 wherein the liquid is an aqueous solution of sodium hydroxide.
12.
Device for monitoring the corrosive, erosive and/or encrusting nature of a liquid with respect to a metallic installation, comprising: an electrochemical measuring cell constituted by a metallic probe and an auxiliary electrode arranged to contact the liquid to create a double layer at the interface between the probe and the liquid; and a component connected to said cell for measuring the differential capacitance of the double layer and the electrical resistance of said cell, which are representative of the surface condition of the probe