Evaluation and Monitoring Methods for Atmospheric Corrosion

Abstract

Conventional electrochemical methods were considered difficult to apply to atmospheric corrosion with hardly to provide an electric current path. Recently, many sensors and measurement methods have been proposed to overcome that problem in corrosion monitoring under atmospheric environmental conditions. In this review, methods and techniques to monitor and evaluate atmospheric corrosion are introduced including an ACM （Atmospheric Corrosion Monitor） type corrosion sensor, which was developed by the authors. For the ACM sensor, it is shown that by analyzing the magnitude and time variation of the sensor output （I）, it is possible to detect the periods of dew, drying, and rainfall and to measure their durations （T_rain, T_dew, T_dry）. And it is also shown that by referencing to the empirical I-RH calibrating curve, it is possible to estimate the amount of sea salt deposition （W_s）. Effects of those environmental factors －RH, W_s, T_rain, T_dew and T_dry, and so on – on the corrosion behaviors of steels - carbon steel, galvanized steel and stainless steels – are discussed. Moreover, the equations to estimate corrosion rate of carbon steel are suggested with those factors and electricity of ACM sensor output.