材料腐蚀微生物腐蚀

1、Influence of a dual-species biofilm on the corrosion of mild steel报告时间：2014.10.14Contents Abstract Introduction Experimental approach Conclusion Results1.AbstractTwo bacterial species: the iron-reducer, Shewanella oneidensis (MR-1), and the sulfate-reducer, Desulfovibrio desulfuricans (G20). Electro

2、chemical impedance spectroscopy (EIS) shows that over a short time period, co-cultures of MR-1 and G20 protect steel from corrosion. its potential applicability to the design of biological corrosion-control measures.2.IntroductionMR-1 can couple the oxidation of lactate to the reduction of poorly cr

3、ystalline ferric (hydr)oxides Fe(OH)3:1/4CH3CHOHCOO-+Fe(OH)3 +2H+1/4CH3COO-+ Fe2+ + 1/4CO2(g) +11/4H2Owhereas G20 can couple the oxidation of lactate to the reduction of sulfate:2CH3CHOHCOO- +SO42-+2H+2CH3COO- +2CO2(g)+ HS-+ 2H2O3.Experimental approach1.菌种来源杀菌 浸入 洗净、挂擦 富集培养经初步分子生物学分析, 该富集细菌中存在IRB和SR

4、B。将培养2 周的混合细菌按10% 体积比接种到试验体系中, 进行相关试验。进一步使用琼脂板固体培养基对富集细菌进行分离纯化。2.对腐蚀产物进行扫描电镜与能谱分析Bacterial biofilms were imaged by environmental scanning electroscopy (ESEM) using a Philips XL30 ESEM-FEG. Samples were viewed using temperature and hydration control provided by a water-cooled Peltier specimen stage.

5、The sample chamber water vapor pressure was 5.0 Torr at a 3.4 . Samples were viewed using an accelerating voltage of 20 keV and a beam spot size of approximately 10 nm at the specimen with a working distance of 10 mm.3.电化学实验（三电极体系、EIS、Nyquist、Bode)Stainless steel 316 SCE实验分组： single-species experime

6、ntsdual-species experimentsMR-1G20NothingMR-1MR-1：G20=10：1MR-1：G20=100：1Electrochemical impedance spectroscopy (EIS) was used to determine how the bacteria influenced the corrosion potential (Ecorr) and corrosion rate of the steel.Impedance spectra were recorded with an applied alternating current s

7、ignal of 10 mV (rms) and a frequency range from 105 to 10-4 Hz using Gamry equipment.EISIn systems with a single relaxation time, Nyquist plots of the real and imaginary impedance spectroscopy data form circles centered on the real impedance axis. In our experiments,Nyquist plots form circles with c

8、enters located below the real impedance axis which is indicative of dispersion in the relaxation time. Our extraction algorithm was successful in extracting Rp values.工作电极和参考电极之间的行为可以用一个RC回路来表示！EIS数据处理的目的主要有两点：(1) 根据测量得到的EIS谱图，确定EIS的等效电路或数学模型；(2) 根据已建立的合理的数学模型或等效电路，确定数学模型中有关参数或等效电路中有关元件的参数值。需要指出的是，由

9、于无法为非法拉第阻纳建立普适性的数学模型，EIS法大多采用等效电路的方法，但该方法遇到以下困难：(1) 一个EIS谱可能对应多个等效电路；(2) 等效电路上阻抗元件的物理意义往往不能够彻底弄清。电极过程的等效电路: RsRct Cd图7-17 含ZW的简单电化学系统电解液电极Rp离子双电层Cd高频低频忽略浓差极化jwbwRpRsXXRRsZZZ1 11p11 jRsRp CdRs Rp Cd Rf Cf 无生物膜等效电路图 有生物膜等效电路图其中： =RpC X=1/(jwC) X=1/(wC) C=bC w=2f j=1-)1 (42222)2()2b (bRpRpRsZRpZ22p)1 (

10、)()1 (1RsbwwjwbwRRsjwbwRZpZ=22)1 ()()1 (sbwwbwRpRZ=22)1 ()(wbwwRp消去w得：This relationship is a circle centered at Z0 = bRp/2 below the Z-axis and at Z0 =Rs +Rp/2 to the right of the Z-axis. Its radius is Rp/2. .The Nyquist equation was fitted to the experimental data.)1 (2b1.The ferrozine assay was us

11、ed to determine Fe(II) concentration.2.A modified methylene blue assay was used to measure sulfide concentration3.Twofold serial dilutions of standard concentrations of Fe(NH4)2(SO4)2 6H2O and Na2S were made for all experiments to create standard curves for ferrozine and sulfide assays, respectively

12、.4.bacterial cell counts.5.pH measurements6.Weight loss measurements4.Results:Enrichments for iron- and sulfate-reducing bacteriaCorrosion characteristics of a single-species systemCorrosion characteristics of a dual-species systemcarbon 1018 coupons Iron- and sulfate-reducers were enriched from the

13、 resulting rusty biofilm (Fig. 1b) by providing either Fe(OH)3 or sulfate as the sole electron acceptor.4.1 Enrichments for iron- and sulfate-reducing bacteriaFig. 2. Chemical and biological composition of the solution above the steel from days 0 to 4 postinoculation for single-species chambers: (a)

14、 planktonic bacterial cell counts for MR-1 and G20, (b) ferrous iron concentration, (c) sulfide concentration and (d) pH.4.2 Corrosion characteristics of a single-species systemFig. 5. ESEM photographs of biofilms formed on steel 4 days post-inoculation: (a) MR-1 only, (b) G20only and (c) 1:1 ratio

15、of MR-1 and G20 together. Scale bar is 10 lm.4.3 Corrosion characteristics of a dual-species systemFig. 6. Chemical composition of the solution above the steel from days 0 to 4 post-inoculation for MR-1only or dual-species chambers: (a) ferrous iron concentration, (b) sulfide concentration and (c) pH.Conclusionu We first verified the existence of these two types of bacteria in a natural biofilm by successfully enriching for iron- and sulfate-reducing bacteria from a biofilm formed on carbon steel in a marine environment.We foun