The Electrochemical Behavior Of Fe-based Glassy Alloy In Alkaline Solution And The Effect Of Magnetic Field On Its Corrosion Resistance

Fe-based amorphous alloys are widely applied in industry due to their high glass-forming ability, ultrahigh strength and hardness, soft magnetic property, good corrosion and wear resistance. In this paper, the effects of scanning rate (v) and NaOH concentration (CNaOH) on the electrochemical behavior of Fe-based glassy alloys in alkaline solution have been investigated. It is found two anodic peaks (P1 and P2) present in the polarization curve of Fe78Si9B13 glassy ribbon in NaCl+ NaOH solution when v is high enough. The former is ohmic resistance controlled, which is dominated by the formation of SiO2 protective film, and the latter is adsorption controlled, accompanying the damage of the SiO2 film. Three corrosion potentials (Ec1, Ec2 and Ec3) are observed in the polarization curves for Fe-based glassy ribbons in OH- contained solutions when v or cNaOH reaches a specific value. Multiple corrosion potentials’ occurrence is explained by a practical anodic and cathodic curve intersection model.In this model, we choose the measured anodic curve as the apparent anodic curve, from it subtract the measured anodic curves with various v or cNaOH and linearly fit the differences as the imaginary cathodic line. By moving cathodic line evenly or rotating it and imposing it with the apparent anodic curve, the number of intersections can be obtained and the number of corrosion potentials can be predicted. The practical model shows that the peak P1 is the necessary condition for the occurrence of three corrosion potentials. The formation of P1 or P2 is closely associated with the composition and microstructure of Fe-based alloys.In addition, the effect of magnetic field on corrosion resistance of Fe78Si9B13 glassy ribbon in alkaline solution has been investigated. It is found that the added magnetic field induces a severe corrosion behavior of Fe-based glassy ribbons despite being in immersion or electrochemical corrosion, reflecting in a larger corrosion rate and a lower pitting potential.In addition, the magnetic field can decrease the charge transfer resistance (Rt) in the equivalent circuit of the electrochemical reaction, can trigger the occurrence of filiform corrosion and cracks, and can hinder the formation of silicon dioxide on the sample surface. The severe electrochemical corrosion of Fe-based glassy alloy under magnetic field is explained by the effects of magnetohydrodynamic (MHD).