CORROSION MONITORING

摘要

Method and apparatus for detecting and measuring localised corrosion of a metallic surface. An array of electrodes fabricated from the same material as the metallic surface is exposed to the same corrosion conditions as the metallic surface. The coupling current between two electrodes of the array is measured, and the electrochemical current noise originating in the electrode array is measured. The two measurements are compared, the electrochemical current noise increasing as compared to the coupling current as the degree to which corrosion is localised increases. The electrochemical current noise originating in the coupled array electrode and the associated electrochemical corrosion potential noise are produced by the natural corrosion processes. The corrosion current is measured by comparison or correlation of the electrochemical current noise and the electrochemical potential noise, the electrochemical potential being measured by means of a third electrode in the array, a reference electrode or a relatively inert electrode. Comparison or correlation of the electrochemical potential noise to the electrochemical current noise provides a resistive noise or impedance, which is inversely proportional to the corrosion current. The corrosion measurement or metal penetration rate is then obtained from the measured corrosion current, as provided by the resistive noise or impedance noise determination, but modified by the degree of localisation, as measured by the electrochemical current noise and coupling current determinations.