2017 Volume 66 Issue 1 Pages 3-12
The laboratory simulation tests which could be reproduced the corrosion reactions propagating in the actual environments were utilized to analyze the mechanism of corrosion phenomena. In this report, some results are introduced in the cases of maritime structures and nuclear facilities.
As for the maritime structures, corrosion maximizing at the portion just under the low water level was focused. The results obtained by the simulation test of marine environments show that this portion acts as anode accompanied by the tidal area as the cathode in the high tide and also acts as anode accompanied by the deeper immersion area as the cathode at the low tide. This portion stayed as anode site for a long time and corrosion amounts are larger than the others. It is estimated that continuous dissolution of this portion changes the circumstantial condition to anode site preferentially. This type of corrosion phenomenon might be called “Tokeguse”; keeping an anode site longer than expected.
As for the nuclear facilities, experimental apparatus was originally designed to obtain the data in high radioactive condition simulating actual plants. One is a result showing the effect of Np ion to the corrosion of stainless steel in nuclear fuel reprocessing plant.
Corrosion mechanism was revealed that Np6+ ion is reduced to Np5+ ion by a corrosion reaction of stainless steel and then re-oxidized to Np6+ ion in the bulk solution. And repetition of this cycle accelerated corrosion of stainless steel by a little amounts of Np addition in nitric acid solution. Another result is introduced that an effect of H2O2 created by radiolysis of cooling water at high radioactive environment in light water reactor.