The Research On The Corrosion Mechanisms Of Sulfate Reducing Bacterial On Metal Materials

Microbiologically Influenced Corrosion caused huge economic losses to the national economy. Sulfate reducing bacterial (SRB) is one of the most important bacterial. It is very important to the actual industrial production to research on the impact factors of SRB corrosion and control methods.In this paper, SRB is isolated and purified by culture dish sandwich anaerobic Method. The effect of SRB on corrosion behavior of low alloy steel, duplex stainless steel and antibacterial stainless steel and the effect law of temperature, pH and velocity on SRB corrosion were investigated by electrochemical testing technique and microorganism analysis. The results show that:Bacilliform sulfate-reducing bacterial attaches and accumulates on local surface of low alloy steel. SRB accelerated corrosion of low alloy steel by anodic depolarization, the reducing order of corrosion resistance is 09Cr2AlMoRe,08Cr2AlMo,10CrMoAl. In SRB medium, the content of S element in corrosion product is 9.23%, which is mainly FeS. Depolarizing agent sulfides concentration increasing with temperature caused corrosion rate increase. Moreover, corrosion reaction follows Arrhenius relation. The corrosion rate is the highest when pH equals to 8.The corrosion rate increase with rotating speed and velocity.Inoculating of SRB into the sterile seawater plus sodium lactate medium, the passive film of duplex stainless steels is damaged; the corrosion potentials turn negative, passive current densities increase. Sterilization rate of antibacterial stainless steel contained copper to SRB is 90.67%. SRB rapidly propagate in logarithmic grow period and form loose biofilm on the surface of NSSAM3, which induces the sensitivity to local corrosion. However, the concentration of Cu2+ in SRB medium increases to 8.590μg/mL from 2.735μg/mL with increasing time, anodic polarization current density of NSSAM3 decreases and polarization resistance increases .XPS indicadesthat the surface film of NSSAM3 with no polshing in SRB is made of FeS,FeS2,FeO,Fe2O3,CrO3 and CrO42-. Compare to sterile medium, the corrosion resistance of NSSAM3 decreases because of chrome oxide being dissolved.When sulfate ion concentration in the medium is lower than 1.0%, its concentration increases will accelerate the SRB induced corrosion. By adding 10 mmol/L of sodium molybdate in bacterial growth beginning, the corrosion rate of 10CrMoAl steel can be significantly reduced. We must add appropriate amount of sodium molybdate before forming a biofilm on the metal surface if we want to prevent SRB corrosion. The minimum bactericidal concentration of Glutaraldehyde and Bromogeramine to 7×104 cfu/mL of SRB are 300mg/L and 60mg/L, respectively. The same concentration Bromogeramine and glutaraldehyde mixed at volume ratio of 1:1.5 have the most efficient sterilization.Titanium dioxide thin film on the surface of 304 stainless steel prepared by sol-gel method and Ni-P-nano-TiO2 composite coatings of electroless plating on carbon steel have a protective role on SRB corrosion, they may still maintain a good corrosion resistance after they were long-term immersed in the SRB bacteria.