添加稀土元素和二氧化硅颗粒的锌铁镀层的腐蚀电化学研究

添加稀土元素和二氧化硅颗粒的锌铁镀层的腐蚀电化学研究
　　In this paper, metal corrosion was narrated, and thermodynamics criterion of metal corrosion was introduced. Besides, electrochemical methods of metal corrosion were stated. Basing on reading mass of datum, electrochemical conosion behavior of five types of ZnFe coating was tested by experiments. Corrosion resistances of five types of coatings were compared, and corrosion mechanisms were preliminarily approached.Tafel polarization curve, Weak polarization curve and Electrochemical impedance spectroscopy (EIS) were adopted to test the corrosion action of the five coatings in quality concentrate 5%NaCl solution as well as volume concentrate 5% H2SO4 medium. The corresponding curves were painted, and the electrochemical parameters of the curves were fitted out. Matching with t3he soaking corrosion, mass change-time graphs were painted, which were about the five coatings and central metals soaking in quality concentrate 5% NaCl solution. Special shape NdFeB magnets Corrosion resistances of five types of Zn Fe coatings were compared through the results of the soaking experiment and soaking experiment and electrochemical method. The influence of the compositions, which were contained in coatings, was tentatively explored.The results of the test indicated: in the coating, Zn and Fe corroded first, which was in accord with thermodynamics criterion and electrochemical corrosion criterion.
　　Observing the surface, we can see: the surface of Zn coating was rough and unsmooth;the surface of Zn-Fe coating was fine and close;and the Zn-Fe-Re coating, as well as Zn-Fe-SiO2 are quite neat and smooth. Contrasting with the soaking experiment and electrochemical method, we can conclude: Five coating materials, Zn/Fe、 Zn—Fe/Fe、 Zn—Fe—Re/Fe、 Zn—Fe—Re/Cu、 Zn—Fe—SiO2/Fe, are chosen to do the test. Tafel plot, also weak polarization curve and Electrochemical impedance spectroscopy have been carried out at 25 °C With the five coatings soaking in the five pieces of 5% NaCl solution as well as 5% H2SO4, Different curves have been printed.. Then we can figure out the relative electrochemical parameters. In contrast to the consequence of the soaking experiment, corrosion resistance has been compared and corrosion mechanism has been approached.Among the five materials, the corrosion resistance of Zn-Fe-SiO2 coating is the best not http://www.999magnet.com/ only in salt solution but also in acid agent, because of putting in the SiO2 particle,which can make the crystalline grain tiny and lower the polarization current, also make the surface smooth. When coating is eroded in medium, SiC>2 particle will form corrosion-products with metal that can decrease the corrosion rate. The corrosion resistance of Zn—Fe—Re/Cu is lower than Zn-Fe-SiO2/Fe in two kinds of corrosion medium, but better than others. The corrosion resistance of Zn—Fe—Re/Fe is good in salt solution, but in acid medium the corrosion resistance is commonly. Zn—Fe—Re composite coating has the finest crystal and uniform surface. When the material is eroded, the corrosion-products can adhere to the surface of coating and decrease the corrosion rate. The corrosion resistance of Zn-Fe/Fe is commonly in both of medium, and corrosion resistance of Zn/Fe is worse than other four materials. Zn-Fe coating is finer and smoother than Zn coating. Zn coating can be passive when it is eroded, but the performance of protection is not satisfactory. This thesis could provide some reference for the improvement of the Zn-Fe electrode position technology.