Shinichi Motoda

Evaluation of Corrosivity in Atmospheric Environment by ACM (Atmospheric Corrosion Monitor) Type Corrosion Sensor

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.

Effect of Thickness of Water Film on Atmospheric Corrosion Behavior of Carbon Steel

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.

Study on Corrosion Control in Reactors Using Radiation Induced Surface Activation (RISA): Mechanism Behind Stainless Steel Durability Due to RISA Against Crevice Corrosion

This study examines a corrosion control technique for corrosion-resistant materials or of stainless steel in piping for nuclear reactors. This employs an effect of Radiation Induced Surface Activation (RISA). The experimental results revealed: (1) The mechanism behind the corrosion control proposed by the previous report was confirmed to be appropriate. This via tests that measured the amount of dissolved oxygen and iron ions, in the solution. (2) The corrosion control technique was confirmed to be useful for stainless steel with any kind of metal oxide film coating on the surface. (3) It was also shown to be useful even in actual seawater, due to biological effects, which is a far more severe environment for corrosion control than simple salt water. The corrosion control technique for corrosion-resistant material using RISA in seawater has therefore been shown to offer a significant potential for practical applications in naval architecture and marine structures.Copyright

Fundamental Study of Corrosion Control in Marine and Offshore Structures Using Radiation Induced Surface Activation (RISA)

A corrosion mitigation technique based on radiation induced surface activation (RISA) from the gamma ray irradiation on a metal surface is reported in this paper. This study aimed to develop a RISA method to prevent crevice corrosion in SUS304 stainless steel using low-intensity radioactive material. Experiment showed that an electrode potential of -100 mV vs. Ag/AgCl was produced and maintained on TiO2-coated SUS304 stainless steel specimens immersed in artificial seawater and in close contact with a small, sealed60Co source or activated by spontaneous neutron irradiation, with no corrosion observed for more than 7 days. On the contrary, the potential of the specimen without a radiation source decreased less than-280 mV vs. Ag/AgCl and crevice corrosion occurred beneath the O-ring within few days. The RISA effect of low-intensity radioactive material has the potential to prevent crevice corrosion of SUS304 stainless steel in actual seawater.