IN-SITU INVESTIGATION OF CREVICE CORROSIO N IN MODEL SYSTEMS USING MINIATURIZED ELECTROCHEMICAL SENSORS

Measuring characteristics of miniaturized sensors for the determinatio n of the parameters pH value, oxygen content, concentration of chlorid e ions and redox potential was tested and optimized with regard to the application in model crevices. The sensors were used for examinations of crevice corrosion in 0.1 molar and 1 molar solution of NaCl at the following alloys: X 20 Cr 13, X 2 CrNi 1810, X 2 CrNiMoN 1713 5, X 2 CrNiMoN 1713 5, X 2 CrNiMo CuN 20 25 6. Corrosion characteristic of t he alloys and the change of crevice electrolyte without external polar ization and with galvanostatic polarization (i = 10 mu A/cm(2), i = 20 0 mu A/cm(2)) were tested and discussed by the hand of the model conce pts from Oldfield and Sutton [1]. In experiments with galvanostatic po larization the steels with increasing content of chromium or molybdenu m showed a growing stability against crevice corrosion. The results sh owed that simultaneous measurements of the above mentioned chemical pa rameters of crevice electrolyte in connection with the corrosion poten tial can supply additional information about causes and mechanism of c revice corrosion.