Evaluation of Galvanic Current Property of ACM Type Corrosion Sensor Consisting of the Fe-C galvanic Couple

Abstract

We fabricated the ACM sensor consisted of a Fe/C-galvanic couple and investigated the sensor output behaviors in outdoor exposure test or in constant humidity test. In the exposure tests of Fukui and Okinawa, the FeC sensor output is almost the same as the FeAg sensor output, but decreases when several days after the start of exposure and during rain period. The FeC sensor output in the I-RH calibration curve increases with increasing an amount of deposited sea salt and a humidity, and is the same as FeAg sensor output when W s is in the range of 0.01 to 1 g/m 2 and RH is 30 to 90. The I gal of the FeC sensor in an artificial seawater drops to 90μA, which is less than 1/3 of that of the FeAg sensor. The cathode current density of the C electrode in an artificial seawater is lower than that of the Ag electrode. By analysis impedance spectrum of the C electrode, the change transfer resistance, R ct increased and the electric double layer capacitance, C dl reduced than that of the Ag electrode. It is considered that the C electrode/liquid interface has reactive resistance to electron transfer in the reduction reaction of dissolved oxygen.