Effect of a Magnetic Field on the Flow Assisted Corrosion of Low Alloy Steel in an Alkaline Solution

Abstract

The effects of a magnetic field on the protective oxide layer of a low alloy steel were evaluated to develop a method to mitigate against feeder wall thinning. A magnet-attached rotating cylinder electrode and piping steel covered with simulated oxide film were used in potentiodynamic test and erosion test to determine the magnetic effect on electrochemical and erosional aspect of the oxide layer, respectively. An electrochemical corrosion reaction was active in the magnetic field because the local mass transfer rate was increased by the magnetohydrodynamic force generated by a coupling of the electric and magnetic field. However, the magnetic field effect decreased with increasing temperature and rotation velocity. Those might be come from the facts that the thickness of the diffusion layer decreased with rotating velocity and the diffusion constant increased with increasing temperature. Actually, the erosion of oxide layer was restrained by the magnetic field, because eroded particles were re-precipitated on the worn oxide surface and interfered with the erodent when the magnetic field was maintained. The effect of the magnetic field on the electrochemical corrosion reaction was reduced with increasing temperature, while the erosive resistance of oxide layer is enhanced by the magnetic field. A permanent magnet may be possibly used as feeder wall thinning mitigation method for nuclear power plants.