Corrosion measuring method for metal material and measuring device therefor

Voltage is applied to a metal electrode in the noble direction with a potential of the metal electrode when it is immersed in an electrolyte solution as an initial potential. Voltage is increased till the material to be measured reaches a passive state and it is kept in the passive potential. Pulse-like voltage signals are applied to the metal electrode in the base direction with the passive potential as a reference potential to measure electric current flowing between the metal electrode and the opposite electrode. A corrosion degree of the material to be measured is obtained by using the value of the electric current. A design for minute electrolytic cells for electrochemical measurement is required for enabling the measurement in fine pipes. A technique which minimizes the amount of electric power supplied to electrochemical cells in order to minimize the composition of the electrolyte and gas generating amount and can detect sensitivity of the object to be monitored is necessary. Accordingly, grain boundary corrosion, especially, sensitivity of the plant constituent materials in a narrowed portion can be measured with small amount of electrolyte solution by using pulse voltage signals. (N.H.)