| As a new branch of the electrochemistry,magnetoelectric chemistry has a potential application in the electrochemical processing,corrosion,and protection of the metallic materials.In recent years,the study of the anodic dissolution process of a metal under an applied magnetic field(MF)has attracted more attention.Because the metallic materials,such as cobalt,brass,304 stainless steel,are often used under the applied MF,to study the effects of MF on the anodic dissolution of these materials is of great theoretical and practical value.Digital holography,a non-destructive and effective technology,can be used suscucefully to observe the dynamic processes at the electrode│solution interface during the anodic dissolution of matals.The aim of this paper is to study effects of MF on anodic dissolution of cobalt,brass,and stainless steel by using electrochemical method ecombined with digital holography,scanning electron microscope(SEM),and X-ray photoelectron spectroscopy(XPS).The main contents of this paper are as follows: 1.Effects of MF on the anodic dissolution of cobalt in phosphoric acid solutionThe anodic dissolution process of Co in phosphoric acid solution was studied under the applied magnetic field,whose direction is perpendicular(B┴)or parallels(B//)to the surface of the Co electrode.It was found that current oscillation occurred during the anodic dissolution of cobalt.After the application of B//,current oscillation were changed to active dissolution;however,those tended to be passive after the application of B┴.In a word,B// enhances the dissolution of the Co | H3PO4 system.On contrary,B┴ suppresses the dissolution of the system.2.Effects of MF on anodic dissolution of HS221 brass in NaCl solutionEffects of MF on anodic dissolution of HS221 brass | NaCl system are studied by using the electrochemical methods combined with the digitial holography.The results show that B// enhances the anodic dissolution of pure copper but inhibit that of pure zinc.MF promotes the dissolution of HS221 brass in the sodium chloride solution because the enhancing effect of B// on copper is more significant than that on zinc.3.Effects of MF on the anodic dissolution of 304 stainless steel in ferric chlorideThe dynamic processes at the electrode | electrolyte has been observed by the in-line digitial holography during the anodic dissolution processes of the 304 SS | FeCl3 system under the applied MF,and the electrode surface atomics’ compositions has been analysised by EDS and XPS.It was found that the effects of MF were different at different electrode potentials because MF has different effects on the different elements of the 304 SS.MF can enhance the anodic dissolution of Fe and Ni,but inhibit Cr.In relatively lower potentials,MF promotes the anodic dissolution of 304 SS,which is due to the promotion of Fe as the main ingredient in 304 SS.However,at higher potentials,EDS and XPS results show that MF made the Cr content of the electrode surface increase and formed a relatively stable oxide film on the surface of the 304 SS electrode easily.Therefore,MF restrains the anodic dissolution of 304 SS at the high potential. |
