Electrochemical measurements of nickel in sodium hydroxide solution with chlorides with and without magnetic field are used to investigate the effect of magnetic field on the anodic behavior and the results of the magnetic field effects on the reaction rates and electrode surface morphology. When polarized at potentials in the passive range such as 0.1 V(SCE), 0.3 V(SCE) and 0.4 V(SCE) , the anodic current decreased after imposing a 0.4 T magnetic field and increased after withdrawing the magnetic field. When polarized at 0.6 V(SCE) and 0.8 V(SCE) potential, Ni was under transpassive dissolution and imposing a 0.4 T magnetic field increased the anodic current while withdrawing the magnetic field decreased the anodic current as the results of magnetohydrodynamic effect. Pit growth period for Ni polarized at 0.8 V(SCE) was enhanced by the applied magnetic field.

The microstructure and the oxide films formed on Ni-base alloy cladding in simulated pressurized water reactor (PWR) primary water environments at 325 o C were characterized. There was a steep drop of iron content and increase of Ni and Cr content in the Ni-base alloy cladding near the fusion line, and a relatively mild drop of iron content and the resultant increase of Ni and Cr contents at the location about 3.8 mm away from the fusion line. The surface oxide morphologies were observed by scanning electron microscopy and the cross-section morphologies and chemical composition of the oxide films were measured by transmission electron microscopy (TEM) and energy dispersive spectrometer. After 146 h immersion in PWR primary water, there were more oxide particles on the cladding alloy at the location closer to the cladding fusion line. After 1860 h immersion in PWR primary water, fine oxide particles on the specimen surface were covered with sparsely distributed large oxide particles. The oxide film after 1860h immersion exhibited a duplex structure, which was thicker at the location closer to the fusion zone, according to TEM results. The outer layer was rich in iron and the inner layer was rich in chromium. Both the inner and the outer oxide films were depleted in Ni, despite of the high Ni content in the alloy matrix.

The effects of magnetic field on anodic dissolution and passivation of iron in a sulfuric acid solution with chlorides are investigated by electrochemical measurements and surface observations. In the anodic potentiodynamic polarization curve, the potential for the drastic current drop is not significantly affected by the potential sweep rate under 0 T, which moves in the negative direction with increasing potential sweep rate under 0.4 T magnetic field that is parallel to the working electrode surface. The uneven surface produced during the potentiodynamic polarization hinders the transition from active dissolution to passivation. The area fraction of the locally accelerated dissolution increases with prolonging polarization time at high potentials where the surface film precipitation-dissolution process is the rate-determining step for metal dissolution. Pretreatment under potentiostatic polarization at 0.4 T magnetic field produces an uneven surface that would result in unrecoverable electrochemical states after switching from 0.4 T to 0 T, depending on the applied potential. The positive-feedback mechanism for the magnetic field effect and the surface morphological effect is proposed. The results demonstrate the direct magnetohydrodynamic effect and its resultant uneven surface on the anodic behavior of iron.

Model alloys 9Cr-25Ni-1.5Mo-5Si and 9Cr-25Ni-1.5Mo-3Si with lower Cr and higher Ni and Si contents than 316L SS were to simulate the grain boundary chemical compositions resulting from irradiation induced segregation in irradiated austenitic stainless steels. The effect of Si-addition in the model alloys on the oxide film formed in alkaline high temperature water at 290 o C was investigated by Raman spectroscopy, scanning electron microscopy and XPS. Compact layer was observed on all the alloys after exposure for 24h or longer. The outer layer oxides on model alloys were larger than that on 316L SS after the same immersion period. The oxide films formed on 316L SS and 9Cr-26Ni-5Si after exposure to the alkaline water at 290 o C for 120 h had a duplex structure. The oxide film formed on 316L SS was thicker than that on 9Cr-25Ni-1.5Mo-5Si alloy. Oxides of silicon was identified in the inner oxide layer 9Cr-25Ni-1.5Mo-5Si alloy but not significant on 316L SS.