Research Of Corrosion Behavior Of Ferroalloys In The Flowing Seawater

With the development of productive force,science and technology,the relationship between the humankind and the ocean becomes closer and closer.Harnessing,exploiting and exploring the ocean have been acknowledged all over the world.Among the problems generated during the exploitation,marine corrosion unavoidably becomes the issue we are faced with and that is urgent to be solved.Concerning the serious corrosion of metallic material in the ocean,developing special marine materials that prevent marine corrosion of metal has become one important academic issue.This research,using the self-made sink-like fluid flowing device of marine corrosion,has explored the electrochemistry corrosion behaviors of several ferroalloy materials including Fe, Fe5Cr,Fel0Cr,Fel5Cr,Fe20Cr,steel 20 and stainless steel 304 in the seawater at the four selected flow velocities(0m/s,0.2m/s,0.3m/s and 0.4m/s) and discussed about it with the electrochemistry testing methods such as potentiostatic polarization and potentiodynamic polarization and basic methodology of materials such as SEM,EDS and XRD.The results of the research have following indications:1.The quality of corrosion resistance of these ferroalloys in the research in the flowing seawater is worse than in the still seawater;the quality of corrosion resistance worsens and velocity of corrosion increases as the flow velocity ranging from 0m/s to 0.4rn/s becomes higher;2.The corrosion process of these ferroalloys in this research is controlled by process of cathode in the seawater at the flow velocities(0m/s,0.2m/s,0.3m/s and 0.4m/s);3.Compared with the still seawater,flowing seawater makes the corrosion electric potential of the selected ferroalloys in the research generate negative shift.The negative shift increases as the flow velocity increases;4.In the still seawater protuberance of corrosion is formed,caused by corrosion,on the surface of pure iron,while in the flowing seawater corrosion pit with an obvious direction is formed,caused by corrosion.The consistency of corrosion substance scales in the corrosion pit and the integration property worsen as the flow velocity ranging from 0m/s to 0.4m/s increases.5.Fe10Cr,Fe15Cr and Fe20Cr,under the condition of potentiostatic polarization (0.5V,25min) generate pit corrosion property of different degrees,pit corrosion property becomes milder when the content of chromium increases;sensitivity increases when flow velocity increases.Stainless steel 304 under potentiostatic polarization(1V,10min) generates obvious pit corrosion.