Vapor corrosion rate monitoring method and apparatus

Claim 1

A vapor corrosion rate monitoring apparatus including a probe comprising: a main planar body having a front face traversed by a test electrode, a reference electrode and two auxiliary electrodes straddling said test electrode; a plate member facing said front face a distance therefrom to define a crevice therebetween; with said main planar body and plate member being of electrically insulating material; the apparatus further including: potentiostat means connected with said test, reference and auxiliary electrodes for deriving potential representative signals between said test and reference electrodes in a test mode and current representative signals between said auxiliary electrodes in a calibration mode; and means for combining said potential and current signals to derive an indication of vapor corrosion rate within said crevice.

Claim 8

A method of measuring corrosion rate in condensed vapor by the electrochemical polarization technique involving: a probe including a main planar body of electrically insulating material having a front face and a reference electrode, a test electrode and two auxiliary electrodes straddling said test electrode, said electrodes being embedded in said planar body up to said front face; a plate member of electrically insulating material facing said front face a distance therefrom to define a crevice there-between; said probe being exposed in said vapor to form a film of vapor condensate in said crevice; the method comprising the steps of: in a calibration mode applying a first AC current of magnitude I through a first current path between said two auxiliary electrodes, measuring the first path resistance R through the condensed vapor and computing from said resistance R the resistivity of said vapor condensate; in a testing mode applying a second AC current of magnitude I' through a second current path between one of said auxiliary electrodes and said test electrode, concurrently measuring a potential decrement between said reference electrode and said test electrode, computing the resistance R' in said second path from said computed resistivity, determining a voltage drop I'R' with said computed resistance R' and compensating said potential decrement with said voltage drop thereby to establish a corrosion rate value.

Claim 9

A method of measuring corrosion rate in condensed vapor by the electrochemical polarization technique involving: a probe including a main planar body of electrically insulating material having a front face and a reference electrode, a test electrode and two auxiliary electrodes straddling said test electrode, said electrodes being embedded in said planar body up to said front face; a plate member of electrically insulating material facing said front face a distance therefrom to define a crevice there-between; said probe being exposed in said vapor to form a film of vapor condensate in said crevice; the method comprising the steps of: in a calibration mode applying a first AC current of magnitude I through a first current path between said two auxiliary electrodes, measuring the first path resistance R through the condensed vapor and computing from said resistance R the resistivity of said vapor condensate; in a testing mode applying a second AC current of magnitude I' through a second current path between one of said auxiliary electrodes and said test electrode, concurrently measuring a potential decrement between said reference electrode and said test electrode, computing the resistance R' in said second path from said computed resistivity, determining a voltage drop I'R' with said computed resistance R' and compensating said potential decrement with said voltage drop thereby to establish a corrosion rate value.