Research For Corrosion Of Sulphate Reducing Bacteria To Copper

In this paper,the topogram character and growth curve of SRB separated from cooling water were studied.The electrochemistry behaviors of SRB to three different copper materials:Hsn70-1A,Hsn70-1AB,BFe30-1-1 were studied by AC impedence method.What's more,the growth process of bio-films of SRB covering on copper surfaces was observed by atomic force microscope(AFM).The adhesive force between the tip of the probe and the surface of bacteria was measured with the force-distance curve of AFM.The result showed that the SRB separated from cooling water is rod-shaped morphology,oval,flagella.And SRB are gram-negative bacteria.In recycle-water, SRB adjust themselves to the environment in the first 2～3days and its average generation time is 5.76h,which is much longer than that in the culture.When in the lag phase,SRB's corrosion to copper metal is not so serious,however,after that,SRB has good avtivity and it will cause serious corrosion to copper meatl.From the analyze values of Resistance in Equivalent for three coper metals,we can see that at the beginning time of immersion,the capacitance of oxidized film on HSn70-1-A and HSn70-1-AB's surfaces decreased and increased after immersed 7d. And then it decreased again,the control factor became to be proliferation which can be explanded that the biofilms on HSn70-1-A and HSn70-1-AB surface has the role of protection for HSn70-1-A and HSn70-1-AB metals.However,the biofilm on the surface of BFe30-1-1 has much un-homogeneity so that the corrosion of BFe30-1-1 was greater.Through AFM,we found that the number of SRB on copper surface became more with the metal immersed in recycle water for a long time.And biofilm which is comprised of microorganism,EPS and corrosion products became thicker and denser. However,the biofilm on BFe30-1-1 surface is much thicker than the biofilm on HSn70-1-A and HSn70-1-AB.What's more,we found that the adhensive force of SRB on BFe30-1-1 surface is much greater than the force of SRB on HSn70-1-A and HSn70-1-AB surface.When corrosion happened,the corrosion pit was more and larger on BFe30-1-1 and the roughness of BFe30-1-1 after removal of biofilm is bigger,the Ra of BFe30-1-1's surface is 87.4nm,61.3nm on HSn70-1-A's surface,and 56.2nm on HSn70-1-AB's surface.So it can be considered to be that BFe30-1-1's corrosion in recycle water is much more serious.