Papers by Author: Wataru Oshikawa

Abstract: Atmospheric corrosion for carbon steel was discussed with taking notice of the relation between the corrosion rate, CR, and the thickness of adsorbed water film, d, onto deposited sea salt. Amount of water adsorbed onto sea salt was measured under various conditions of amount of deposited sea salt, Ws, and relative humidity, RH. Derived concentration of the solution film was compared with that calculated thermodynamically. Corrosion amount of carbon steel specimens exposed for a month under various Ws and RH was measured and CR along with d were obtained for each condition. The relations of CR to d had the same tendency as is found on “moist corrosion” and “wet corrosion” in Tomashov’s model; However, it showed a maximum CR = 0.29mm/y at d = 56µm, thicker than that reported by Tomashov.

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, Train, Tdew and Tdry, 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 both indoor and outdoor sites by analyzing sensor output. Corrosivities of some kinds of exposure sites, not only outdoor environments but also indoor environments, were evaluated by using the ACM sensor.