Maruthamuthu, S. et al. - Teesside's Research Repository

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Abstract Impact of ammonia producing Bacillus sp. on corrosion of cupronickel alloy 90:10 S. MARUTHAMUTHU a* , P. DHANDAPANI a , S. PONMARIAPPAN b , JEONG-HYO BAE c , N. PALANISWAMY a & PATTANATHU K.S.M. RAHMAN d a Microbial corrosion, Garrett block, Corrosion Protection Division, Central Electrochemical Research Institute, Karaikudi – 630 006. b Division of Biotechnology, Defence R & D Establishment Ministry of Defence, Gwalior - 474 002, M.P . c Electrokinetic Research group, Electrotechnology Research Institute, Changwon city, Gyengsangnam-do 641-120, Korea and d Biotechnology Research Cluster, School of Science and Technology, University of Teesside, Middlesbrough –TS13BA, Tees Valley, U.K. The objective of the present investigation is characterization of ammonia producing bacteria (Bacillus sp.) and its impact on biodeterioration of cupronickel alloy 90:10. It is well known that iron sulphate and molybdenum are good inhibitors used in cooling water system. The role of interaction between inhibitor and ammonia producing bacteria on corrosion of cupronickel 90:10 was studied. Cupronickel coupons were immersed in Chavara rare earth containing backwater for a period of six months. The predominated ammonia producing bacteria were isolated from the six months old biofilm. A total of four ammonia producing Bacillus sp. (AG1-EU202683; AG2-EU202684; AG3- EU202685 and AG4-EU202686) were isolated from the biofilm and identified by 16S rRNA gene sequencing. The corrosion rate of cupronickel in water (System I) was in the range of 0.046mm/year and 0.052mm/year. In the control system II (Chavara water and nitrogen free medium without bacteria), the corrosion rate was 0.008 mm/year whereas in the presence of Bacillus sp. AG1 and AG3, the corrosion rate was in the range of 0.023 and 0.030mm/year. These bacteria fixed atmospheric nitrogen for their cell protein synthesis and converted into ammonia. Ammonia enhanced pH and ammonical solution was formed in the presence of Bacillus sp. that acted as an etchant. The presence of some anodic spots in the presence of bacteria was affected by ammonia and underwent pitting 1
corrosion. The present study reveals that Bacillus sp. encourage intergranular attack without any stress to the cooling water system. Keywords: Microbial corrosion, ammonia producing bacteria, Bacillus sp., copper alloys intergranular attack, inhibitors, cooling water system *Correspondence: Dr Maruthamuthu Sundram, Corrosion Protection Division, Central Electro Chemical Research Institute (CECRI), Karaikudi – 630 006, India. Email: biocorrcecri@gmail.com; Present address: Electrokinetic Research group, Electro technology Research Institute, Changwon city, Gyengsangnam-do 641-120, Korea Introduction The biofilms are important in a wide spectrum of industrially relevant situations and lead to microfouling and microbially influenced corrosion (Lapin-Scott and Costerton, 1989; Bott et al., 1993). Copper and its alloys are most commonly used in the fabrication of heat exchangers in cooling water system. The alloys depend on their natural oxide for corrosion resistance. Corrosion of copper occurs with the outward movement of the cuprous ion rather than the inward movement of oxygen (Rao and Nair, 1998). The slime layer forms a sticky surface, which allows silt and other suspended particles to adhere to the condenser tubes, there by enhancing the aggregation of deposits on the material surface that increased fluid frictional resistance and heat transfer resistance (Bott et al., 1995) in cooling water system. Pope et al., (1984) have documented MIC of cupronickel (90:10), admirably brass and aluminum brass in cooling system of freshwater and backwater. It was also reported that copper alloy condenser tubes had under-deposit corrosion due to the formation of slime deposits and ammonia (Little and Wagner, 1996), which led to stress corrosion cracking (Little et al., 1991). Iron sulphate and molybdate (Oung et al., 1998) are added in many cooling water system as corrosion inhibitors (Uhlig, 1994). It is also well known that iron and molybdate (Oelze et al., 2000; Smith et al., 1999) act as co-factors for bacterial nitrogenase enzyme. Earlier metallurgical analyses of the failed tubes revealed that the tubes were damaged due to stress corrosion cracking (Agarwal et al., 2003; Venugopal and Rawat, 1991). However, no systematic study has been carried out on the interaction between microbial biofilms and corrosion 2
Page 1: This full text version, available o
Page 5 and 6: method. The pure cultures were stor
Page 7 and 8: Open circuit measurements (OPC) wer
Page 9 and 10: model Pico scan 2100 (Molecular Ima
Page 11 and 12: Weight loss Corrosion rate of cupro
Page 13 and 14: Surface analysis by X-ray diffracto
Page 15 and 16: nitrogen with available iron and mo
Page 17 and 18: electrochemical dissolution of meta
Page 19 and 20: Grasshoff K, Kremling K, Ehrhardt M
Page 21 and 22: Reddy GSN, Agarwal RK, Mastumoto GI
Page 23 and 24: Table II. Biochemical test for ammo
Page 25 and 26: Table IV. Corrosion rate of cuproni
Page 27 and 28: Table VII. Energy Dispersive X-ray
Page 29 and 30: 100 Figure 2. UPGMA phenogram showi
Page 31 and 32: Figure 4. Polarization studies for
Page 33 and 34: Figure 6. FTIR study for cupronicke
Page 35 and 36: Figure 8. XRD spectrum for cupronic
Page 37 and 38: Figure 10. Cupronickel metal surfac
Page 39 and 40: Figure 12. Energy Dispersive X-ray
Page 41: Figure 14. Mechanism of MIC on Cupr

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