| 304 stainless steel has good corrosion resistance,mechanical properties and processability,and has a wide range of applications in industrial fields and daily life.Refining grain can improve the mechanical properties and irradiation resistance of 304stainless steel materials,but nanocrystalline materials have a large number of high-activity grain boundaries,which in turn affects their corrosion resistance.The in-depth study of the corrosion resistance mechanism of nanocrystalline 304 stainless steel is important for the development of nanocrystalline stainless steel materials with high corrosion resistance.In this paper,nanocrystalline 304 and 1 at%La doped 304（304-La）stainless steels with an grain size distributed between 30 and 50 nm were successfully prepared using powder metallurgy and high-temperature/high-pressure techniques.Taking 304 commercial coarse-grained stainless steel（with an grain size of about 50μm）as a comparison,the corrosion behavior of 304 and 304-La nanocrystalline stainless steesl was studied by a corrosion loss method,a kinetic potential polarization potential method,electrochemical impedance spectroscopy,etc.,and by observing the surface morphology and products after corrosion using scanning electron microscopy,The corrosion behavior of 304 and 304-La nanocrystalline stainless steels in a 6 wt.%FeCl3 solution was studied.The effect of annealing temperature on the corrosion resistance of 304 nanocrystallin stainless steel before and after La doping was studied.The corrosion resistance of 304 nanocrystalline stainless steel in FeCl3 solution is worse than that of commercial 304 coarse-grained stainless steel.The corrosion weight loss experiments indicate that the corrosion rate of 304 commercial coarse-grained stainless steel is slowly increased whereas that of 304 nanocrystalline stainless steel is increased rapidly,and the corrosion rate of 304 commercial coarse-grained stainless steel is lower than that of304 nanocrystalline stainless steel.In the potentiodynamic polarization curve,the corrosion current density of nanocrystalline 304 stainless steel is higher than that of commercial 304coarse-grained stainless steel.The decrease in the arc resistance radius of the AC impedance spectrum and the negative shift of its corrosion potential indicate that the corrosion rate of nanocrystalline 304 stainless steel in 6 wt.%FeCl3 solution is faster and the corrosion resistance is lower.Through the analysis of the kinetic potential polarization curve and AC impedance spectrum,it is found that the corrosion resistance of the annealed 304nanocrystalline stainless steel is weaker than that of the pre-annealed sample.304-La nanocrystalline stainless steel has better corrosion resistance than 304commercial coarse-grained stainless steel.In the corrosion loss experiment,the corrosion current density of 304-La nanocrystalline stainless steel is the first to achieve dynamic equilibrium and the corrosion rate iis lower;in the dynamic potential polarization corrosion curve,the corrosion current density of 304-La was 0.007842 mA/cm2,which is lower than that（2.262 mA/cm2）of commercial 304 coarse-grained stainless steel,and the transfer resistance Rct of 304-La sample is 13530Ω·cm2,which is higher than the Rct（168.7Ω·cm2）of commercial 304 coarse-grained stainless steel sample.The above results show that the incorporation of La element improves the corrosion resistance of 304 nanocrystaline stainless steel. |
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