Evaluation of Corrosivity of Atmosphere by ACM Type Corrosion Sensor

Abstract

An ACM (Atmospheric Corrosion Monitor) type corrosion sensor, consisting of a Fe-Ag galvanic couple was developed and applied for the evaluation of corrosivity of atmospheric environments. The sensor was designed considering mass-production and good reproducibility of results, making it convenient for long-term corrosion data acquisition. Besides the sensor output, I, temperature, relative humidity, RH, were also recorded by a microcomputer. By analyzing the magnitude and time variation of I, the occurrence and duration of rain, dew and dry periods, T_rain, T_dew and T_dry, respectively, could be distinguished and determined. And by referencing to the empirical I-RH calibrating curve, the amount of deposited sea salt, Ws, could also be estimated. It was also found that the corrosion loss could be estimated in the indoor site by analyzing sensor output. Corrosivities of some kinds of exposure sites were evaluated by using the ACM sensor. It was also demonstrated that this ACM sensor could be applicable to the evaluation of corrosivity of atmosphere for stainless steels.