Investigation of Oxides Formed in the Corrosion of SUS-304 in High-Temperature Water Through the Measurement of Evolved Hydrogen and Radiochemical Analyses

Corrosion behavior of SUS-304 at 280°C in deaerated water has been traced both through measuring H₂ gas, concomitantly formed with corrosion, and through radiochemical analysis of the corrosion layers. The calculated H₂ yield based on the reaction,

M + x.H2O =	MOx + x.H2
	(M: iron, chromium, nickel, manganese, and cobalt) ,

agreed reasonably well with the observed H₂ yields, showing that iron is mainly in a magnetite form and chromium is in a Cr(III) state. More than 85% of the corrosion layers were recovered by repeating ultrasonic cleaning and electrostripping processes. The residual fraction was rich in chromium and dissolved in the subsequent electropolishing process. The total corrosion increases with the reaction time, although the “inner layer”  tends to stay almost constant at a longer reaction time. In some cases, both neutron irradiated and nonirradiated SUS coexisted. Mutual transfer of the elements from one SUS to the other has been examined.