Methods and techniques to monitor and evaluate corrosivities in atmospheric environments are introduced including an ACM (Atmospheric Corrosion Monitor) type corrosion sensor, which was developed by authors. For the ACM sensor, the occurrence and duration of rain, dew and dry periods, Train, Tdew and Tdry, respectively, could be distinguished and determined by analyzing the magnitude and time variation of sensor output, I. And by referencing to the empirical I-RH calibrating curve, the amount of deposited sea salt, Ws, could also be estimated. Effects of those environmental factors - RH, Ws, Train, Tdew and Tdry, and so on - on the corrosion behaviors of steels - carbon steel, galvanized steel and stainless steels - are discussed. Moreover, equations to estimate corrosion rate of carbon steel were suggested with those factors and electricity of ACM sensor output.
Improvement of corrosion resistance of a thin cobalt film by the surface treatment using 1, 2-Bis(triethoxysilyl) ethane (BTSE) was evaluated. A BTSE layer was formed on cobalt oxide by immersing the cobalt film in a BTSE solution including water and hydrogen peroxide which improved corrosion resistance of the film significantly. When hydrogen peroxide was absent in the BTSE solution, the BTSE layer was not formed. The corrosion resistance was improved with increasing the pH of BTSE solution containing hydrogen peroxide. These behaviors could be explained by the hard and soft acid-base (HSAB) principle.
The propagation behavior of crevice corrosion on SUS304 was investigated by the new crevice corrosion test apparatus. The corrosion area and corrosion current in glass/metal crevice can be measured at the same time by this apparatus. The specimen was polished just before the crevice corrosion test under the constant potential condition, E=299 mV, 399 mV and 499 mV (SHE), in artificial seawater at room temperature. Some important results were obtained. The crevice corrosion initiation time tVI determined by the visual observation was coincident with tINCU determined by the current density change. The crevice corrosion area, ACREV, increased exponentially with time from the crevice corrosion initiation time. However, the increasing rate of the crevice corrosion volume, VCREV, changed at the time, tR, which crevice corrosion reached at the edge of crevice. We divided the corrosion process into two stages, Region I and Region II. Region I and Region II are defined as the time region before and after tR respectively. The increasing rate of VCREV in Region II was larger than that in Region I. However, the increasing rate of ACREV in Region I was slightly larger than that in Region II.