Electrochemical Hydrogen Permeation Test under Controlled Temperature and Humidity after Outdoor Exposure at Beijing, Chongqing and Okinawa

摘要

Electrochemical hydrogen permeation tests were carried out under controlled temperature and humidity using pure Fe sheet specimens outdoor-exposed at Beijing and Chongqing, China and Okinawa, Japan in order to understand the effect of environmental factors on hydrogen uptake behavior. The maximum hydrogen permeation current densities of the exposed specimens were in the order of Beijing > Chongqing Okinawa, while the order of the degree of corrosion of the specimens was Okinawa > Chongqing Beijing. X-ray fluorescence analysis showed that the surface concentrations of sulfur on the Beijing- and Chongqing-exposed specimens were higher than that of the Okinawa-exposed specimens, whereas chlorine concentrations of the Beijing and Okinawa-exposed specimens were higher than that of the Chongqing-exposed specimen. Nitrate concentrations of Beijing- and Chongqing-exposed specimens evaluated using nitrate test strips were obviously higher than that of the Okinawa-exposed specimens. It is suggested that air pollutants such as SO_2 and NO_2 and particulate matters containing inorganic acid ions, likely surfate and nitrate ions, and possibly organic acids contribute to acidification of rust layer leading to the enhanced hydrogen entry.