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.

The amount of hydrogen in steel that affects hydrogen embrittlement is considered to be changed with the amount of corrosion of the steel. The authors have found a relationship between the depth of snow and the amount of corrosion. In this study, the hydrogen content was examined and no correlation was found with the amount of corrosion. Under thin solution layer formed by melting snow, the main cathodic reaction is reduction of dissolved oxygen and hydrogen generation reaction is slight. The large amount of surrounding water also suppresses the acidification of the thin solution layer on the specimen, suggesting that the reaction from H_ad to H_ab by H^＋ formation and electron transfer is small.

In order to evaluate the effects of dissolved oxygen concentration on the radiolytic water quality within the cracks of stress corrosion cracking （SCC） under irradiation and the spatial distribution of water quality along the depth axis during irradiation, we conducted immersion tests of stainless steel with a crevice gap and computational simulations of water radiolysis. It has been confirmed that Fe₂O₃ is formed throughout the entire crevice region, irrespective of the dissolved oxygen concentration. Furthermore, it has been estimated that oxidant species generated by radiolysis within the crack are consumed by the growth of oxides under irradiation, and that the reduction in pH at the crack tip occurs by hydrolysis of dissolved metallic elements and enrichment of anions.