(A) study on the effect of magnetic field on the resistance of flow-accelerated corrosion

Abstract

In this study, it was considered that Flow-Accelerated Corrosion (FAC) was caused by reduction of magnetite. thus the effect of magnetic field on the magnetite which was ferromagnetic material was evaluated for developing the mitigation method of FAC. Test material used in the test was SA106 Gr.C steel which was covered with simulated oxide film. Polarization test and erosion test were performed using rotating cylinder electrode (RCE) system. Both of the electrochemical and mechanical aspect could be associated with the polarization test and erosion test. In the results of electrochemical test, electrochemical corrosion reaction was brisk in the magnetic field to not matter with existence of oxide film. This phenomenon was explained that the local mass transfer rate was increased by magnetohydrodynamic force generated by the coupling of the electric and magnetic field. However, current density was decreased with increase in magnetic field at low potential, at which hydrogen evolution reaction was dominant and hydrogen transfer rate was the controling step of total reaction rate. When the magnetic field existed, hydrogen escape rate through the oxide film was reduced and cluster was made by hydrogen bubble. Thus reaction rate at low potential was reduced by magnetic field. Erosion rate of oxide film was increased with increase in particle concentration and rotating velocity, and was decreased with increase in magnetic field intensity. Because the eroded particles re-precipitated on the oxide surface and interfered with erodent when the magnetic field existed.