ie1023707

Published: May 29, 2011

r 2011 American Chemical Society 8006 dx.doi.org/10.1021/ie1023707 | Ind. Eng. Chem. Res. 2011, 50, 8006–8015

ARTICLE

pubs.acs.org/IECR

Microbial Corrosion in Petroleum Product Transporting PipelinesSundaram Maruthamuthu,*,† Baskaran Dinesh Kumar,† Shanmugavel Ramachandran,†

Balakrishnan Anandkumar,‡ Seeni Palanichamy,§ Maruthai Chandrasekaran,† Palani Subramanian,† andNarayanan Palaniswamy†

†Corrosion Protection Division, CSIR-Central Electrochemical Research Institute, Karaikudi, 630 006 Tamil Nadu, India‡Corrosion Science and Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India§Offshore Platform and Marine Electrochemistry Centre, CECRI Unit, Harbour Area, Tuticorin 630 004, India

ABSTRACT: Petroleum product pipelines in India contain large numbers of various types of microorganisms that either directly orindirectly enhance corrosion. Field studies have been carried out by CSIR-CECRI to investigate the corrosion problem in petroleumproduct transporting pipelines in South India. Although Unicor J inhibitor was added in the pipeline to control corrosion, corrosionproducts were detected in the pipeline. The present study reveals that the degradation of the inhibitor enhances the proliferation ofbacteria, which enhances the corrosion. The selection of an inhibitor to control corrosion has also been done.

1. INTRODUCTION

Organic film-forming inhibitors used in the oil and gasindustry are generally of the cationic/anionic type and includeimidazolines, primary amines, diamines, amino amines, oxyalky-lated amines, fatty acids, dimer�trimer acids, naphthaneic acid,phosphate esters, and dodecyl benzene sulfonic acids. Organiccorrosion inhibitors adsorb on the metal surface and form acomplex that inhibits corrosion. Their mechanism of action is toform a persistent monolayer film adsorbed at the metal/solutioninterface. In recent years, microbiologically influenced corrosionhas gained substantial interest and importance.1�4 The identifi-cation of heterotrophic bacteria, iron bacteria, and sulfate-redu-cing bacteria (SRB) in biofilm consortia indicates the role ofparticular bacteria in the process of corrosion in pipelines andseawater injection systems.3�6 It is well-known that bacteria canoxidize a wide variety of chemicals and use them as nutrientsources and enhance the proliferation of bacteria.7,8 Microorgan-isms influence the corrosion by altering the chemistry at theinterface between the metal and the bulk fluid9,10 throughbiogenic MnO2 deposition, conversion of ferrous to ferric ions,pitting by sulfuric acid production,11 and degradation of corro-sion inhibitors.12 In pipelines, hydrocarbon and water stratify atthe bottom of the line when the velocity is less than that requiredto drain the liquids through the pipeline, and hydrocarbondegradation by microbes occurs easily at the liquid interfaceand enhances corrosion.10�12 Recently, the degradation ofcorrosion inhibitors in petroleum product pipelines in North-west India and its impact on bacterial corrosion have beeninvestigated.12

In the present study, we consider a cross-country pipeline(API 5LX G 52) in South India that transports petroleumproducts such as kerosene, petrol, and diesel. This pipeline hasintermittent petroleum product delivery with pressure boostingstations at different locations. The length of the pipeline is 680km. Provisions for the collection of corrosion products are alsoavailable at all stations except at the originating station. Themuckis pushed out of the pipeline by pigs (cylindrical devices that

move with the flow of oil and clean the pipeline interior). Pigs areintroduced into the pipeline in the preceding station and receivedat the following station. Severe corrosion and microfoulingproblems are faced in the pipeline, even though a corrosioninhibitor (Unicor J) (4 ppm) was added. The corrosion inhibitorcontains unsaturated dimeric fatty-acid-based components. Inthe present study, the distribution of bacteria, degradation ofinhibitor, and selection of inhibitor were studied, and the reasonsfor corrosion are explained.

2. EXPERIMENTAL MATERIALS AND METHODS

2.1. Sample Collection and Bacterial Enumeration. Corro-sion products were collected using sterilized conical flasks atvarious sites, namely, stations 1�4, during pipeline pigging. Thesamples collected were transported in an icebox from varioussites to the CECRI Microbiology Laboratory. The collectedsamples were serially diluted (10-fold) using 9 mL of steriledistilled water blanks, and the samples were plated by the pourplate technique.11

2.2. Identification of Bacteria. Genomic DNA of the bacter-ial isolates was extracted according to the method of Ausubelet al.13 Amplification of gene-encoding small-subunit rRNA wascarried out using eubacterial 16S rDNA primers [forwardprimer 50-AGAGTTTGATCCTGGCTCAG-30 (E. coli posi-tions 8�27) and reverse primer 50-ACGGCTACCTTGTTACGACTT-30 (E. coli positions 1494�1513); Weisburg et al.14].Polymerase chain reaction (PCR) was performed with 50 μL of areaction mixture containing 2 μL (10 ng) of DNA as thetemplate, each primer at a concentration of 0.5 μM, 1.5 mMMgCl2, and each deoxynucleoside triphosphate (dNTP) at aconcentration of 50 μM, as well as 1 μL of Taq DNA polymerase

Received: November 24, 2010Accepted: May 29, 2011Revised: May 17, 2011

8007 dx.doi.org/10.1021/ie1023707 |Ind. Eng. Chem. Res. 2011, 50, 8006–8015

Industrial & Engineering Chemistry Research ARTICLE

and buffer as recommended by the manufacturer (MBIFermentas). PCR was carried out with a Mastercycler Personalinstrument (Eppendorf) using the following program: initialdenaturation at 95 �C for 1 min; 40 cycles of denaturation (3min at 95 �C), annealing (1 min at 55 �C), and extension (2 minat 72 �C); followed by a final extension (at 72 �C for 5 min). Theamplified product was purified using GFX PCR DNA and GelBand Purification kit (Amersham Biosciences) and cloned inpTZ57R/T vector according to the manufacturer’s instruction(InsT/Aclone PCR Product Cloning Kit, MBI Fermentas), andtransformants were selected on LB medium containing ampicil-lin (100 μg/mL) and X-gal (80 μg/mL). DNA sequencing wascarried out using ABI PRISM 310 Genetic Analyzer (PE AppliedBiosystems). For the sequencing reaction, Big Dye Ready Reac-tion DyeDeoxy Terminator Cycle Sequencing kit (Perkin-Elmer) was used.2.3. Chemical Characterization of Corrosion Pro-

ducts. 2.3.1. Chemical Analysis of Corrosion Products. Five gramsof corrosion product was mixed with 50 mL of triply distilledwater and sonicated for 1/2 h. After sonication, the samples werefiltered, and the filtrates were used for chloride and sulfateanalysis. Chloride was estimated by theMohr method and sulfateby the gravimetric method.11

2.3.2. XRD Analysis. Corrosion product collected during pig-ging of the pipeline from the various field stations was dried and

crushed to a fine powder and used for XRD analysis to determinethe nature of the complex formed on the pipeline in fieldconditions.15 A computer-controlled XRD system, JEOL modelJDX-8030, was used to scan the corrosion products (collected atdifferent IOC pumping stations) between 10� and 85� 2θ withCu KR radiation (Ni filter) at a rating of 40 kV and 20 mA.2.3.3. FTIR Studies. A Bruker Sensor 207 model Fourier

transform infrared (FTIR) spectroscopy system was used forthe analysis of the corrosion products. The spectrumwas taken inthe mid-IR range of 400�4000 cm�1 with 16 scan speed. Thesamples were mixed with spectroscopically pure KBr in the ratioof 1:100, and the pellets were fixed in the sample holder foranalysis.2.3.4. NMR Studies. 1H NMR (Bruker, 400 mHz) analysis was

used to detect the protons of the nuclei, and 13C NMR analysiswas used to detect the 13C isotope of carbon, whose naturalabundance is only 1.1% in the corrosion product. The sample ofcorrosion product and corrosion inhibitor was dissolved usingdeutrated chloroform solvent.11

2.4. Biodegradation of Inhibitor. In the present study,commercially available corrosion inhibitor used in petroleumproduct transporting pipelines was evaluated to determine thenature of the degradation process. The medium used for detect-ing the corrosion inhibitor degradation process was BushnellHass broth (magnesium sulfate, 0.20 g/L; calcium chloride,0.02 g/L; monopotassium phosphate, 1 g/L; dipotassium phos-phate, 1 g/L; ammonium nitrate, 1 g/L; ferric chloride, 0.05 g/L;Hi-Media, Mumbai, India). Three sets of Erlenmeyer flasks wereused for the corrosion inhibitor (Unicor J) degradation studiesusing the selected bacterial strains as was done in previousstudies.11,12,16,17

2.5. Corrosion Studies. Corrosion studies were performedusing the rotating-cage method.18 API 5LX G52 (C, 0.29 max; S,0.05 max; P, 0.04 max; Mn, 1.25 max) coupons of size 2.5 cm �2.5 cm were mechanically polished to mirror finish and thendegreased using trichloroethylene. The corrosion rate was calcu-lated by the equation19

corrosion rate ðmmpyÞ ¼ weight loss ðmgÞ � CKarea ðin:2Þ � time ðhÞ

Table 1. Weights of the Corrosion Products Collected atVarious Stations

date of sample collection station quantity (kg)

Sep 24, 2009 1 3

Sep 26, 2009 2 a

Sep 27, 2009 3 >10

Sep 28, 2009 4 a

Jan 24, 2010 1 3

Jan 26, 2010 2 a

Jan 28, 2010 3 >10

Mar 30, 2010 4 a

aNegligible.

Table 2. Bacterial Count (CFU/g) of Corrosion Product Collected from Different Stations in September 2009

station and date of collection heterotrophic bacteria iron-oxidizing bacteria acid producers manganese oxidizers sulfate-reducing bacteriaa

station 1 (Sep 24, 2009) 4 � 105 3.0 � 105 5.3 � 104 3.5 � 105 2.1 � 104

station 2 (Sep 26, 2009) 3.0 � 106 12 � 104 6.9 � 105 1.3 � 106 1.8 � 102

station 3 (Sep 27, 2009) 2.1 � 107 24 � 104 3.5 � 104 5.4 � 105 2.4 � 104

station 3 water (Sep 27, 2009) 9 � 104 10 � 104 6 � 102 4.8 � 104 1.7 � 104

station 4 (Sep 28, 2009) 10 � 105 15 � 104 11 � 104 5.4 � 105 2.4 � 104

a Sulfate-reducing bacteria were found in API agar plates but not in API broth.

Table 3. Bacterial Count (CFU/g) of Corrosion Product Collected from Different Stations in January 2010

station and date of collection heterotrophic bacteria iron-oxidizing bacteria acid producers manganese oxidizers sulfate-reducing bacteriaa

station 1 (Jan 24, 2010) 3 � 105 2.8 � 105 4.3 � 104 2.5 � 105 �station 2 (Jan 26, 2010) 2.8 � 106 8.0 � 104 4.8 � 105 1.3 � 105 �station 3 (Jan 28, 2010) 2 x107 21 � 104 2.8 � 104 4.6 � 105 �station 4 (Jan 28, 2010) 7.2 � 105 12 � 104 9 � 104 4.8 � 105 �storage tank water (May 2010) 6 � 104 9 � 104 5 � 102 3.8 � 104 �

a Sulfate-reducing bacteria were not found in the second collection of both API agar plates and API broth.



where C is a constant (if weight loss is in milligrams, area is insquare inches, and time is in hours, the value ofC is 67.7) andK isa density factor (for carbon steel, K = 1). Note that mmpyrepresents the units millimeters per year.

3. RESULTS AND DISCUSSION

3.1. Weights of Corrosion Products Collected from Var-ious Stations. Table 1 lists the weights of corrosion productscollected from various stations. The weight of the corrosionproduct at station 1 was about 3 kg, whereas that at station 3 wasabove 10 kg. Negligible amounts of corrosion product wereobtained at stations 2 and 4. The corrosion products werecollected in the sumps by the owner of the pipeline, which doesnot give the true picture of the actual weight of the corrosionproducts. The fact that the amount of corrosion product washigher at station 3 might be due to the stop mode of operation ofthe pipeline. It is strongly believed that the corrosion was higherat station 3 because of water stagnation in the pipeline.3.2. Enumeration ofMicrobes.Tables 2 and 3 report the data

on the different types of bacteria (heterotrophic bacteria, acidproducers, iron bacteria, sulfate-reducing bacteria, and manganese

oxidizers) enumerated in the corrosion products collected fromfour different stations during September 2009 and January 2010.The bacterial counts were in the range between 102 and 107 colonyforming units (CFU)/g. It can be seen from Tables 2 and 3 thatheterotrophic bacteria, acid producers, iron bacteria, sulfate-redu-cing bacteria, and manganese oxidizers were in the range between104 and 107 CFU/g. It is also inferred from the data that there wasnot much of variation in the bacterial counts of all of the samplescollected from the different stations. Table 2 shows that thebacterial count of SRB was in the range between 102 and 104

CFU/g when the API agar plate was used. When API broth wasused, SRB could not be detected in the first collection inSeptember 2009. In the second collection (Table 3), SRB couldnot be detected in either API agar or broth. This indicates that the

Table 5. Identification of Different Types of Bacteria fromStation 2 Corrosion Product

sample no. sample code identified isolate

Iron Bacteria

1 TIOB3 Bacillus licheniformis

2 TIOB6 Bacillus cereus

3 TIOB5 Lysinibacillus sphaericus

4 TIOB2 Bacillus subtilis

Heterotrophic Bacteria

5 THB16 Citrobacter sedlakii

6 THB17 Klebsiella pneumoniae

7 THB13 Citrobacter sp.

Acid Producers

8 TAP7 Bacillus carboniphilus

9 TAP6 Bacillus caldolyticus

10 TAP21 Pantoea agglomerans

11 TAP3 Geobacillus stearothermophilus

Manganese Oxidizers

12 TMN8 Pseudomonas aeruginosa

13 TMN2 Lysinibacillus boronitolerans

14 TMN3 Bacillus pumilus

15 TMN4 Pseudomonas stutzeri

16 TMN7 Pseudomonas xanthomarina



1 AS Pseudomonas alcaligenes

2 AS2 Pseudomonas stutzeri

3 AS4 Klebsiella oxytoca

4 AS5 Bacillus cereus

5 AS6 Pseudomonas acetoxians




1 SHB1 Lysinibacillus fusiformis

2 SHB4 Pseudomonas stutzeri

3 SHB5 Serratia liquefaciens

4 SHB4 Pseudomonas stutzeri

5 SHB5 Serratia liquefaciens

Acid Producers

6 SAP1 Arthrobacter sp.

7 SAP2 Enterobacter aerogenes

Manganese Oxidizers

8 SMN1 Escherichia coli

9 SMN2 Citrobacter freundii



Iron Bacteria

1 MIOB9 Bactericera cockerelli

2 MIOB13 Pseudomonas aeruginosa

3 MIOB13 Pseudomonas entomophila

4 MIOB5 Citrobacter sedlakii


5 MHB5 Pseudomonas monteilii

6 MHB4 Pseudomonas putida

7 MHB1 Bacillus cereus

8 MHB4 Pseudomonas luteola

9 MHBC Bacillus alcalophilus

Acid Producers

10 MAP3 Vibrio sp.

11 MAP1 Klebsiella pneumoniae

12 MAP2 Vibrio sp.

Manganese Oxidizers

13 MMN3 Bacillus sp.

14 MMN1 Pseudomonas otitidis

15 MMN3A Klebsiella pneumoniae



influence of SRB on the corrosion of the pipeline is negligible.Tables 4�7 report the different types of bacteria identified in thecorrosion products collected from various stations.Bactericera cockerelli, Pseudomonas aeruginosa, Pseudomonas

entomophila, Citrobacter sedlakii, Pseudomonas monteilii, Pseudo-monas putida, Bacillus cereus Pseudomonas luteola, Bacillus alcalo-philus, Vibrio sp., Klebsiella pneumoniae, Bacillus sp., Pseudomonasotitidis, Bacillus licheniformis, Lysinibacillus sphaericus, Bacillussubtilis, Citrobacter sedlakii, Bacillus carboniphilus, Bacillus caldo-lyticus, Pantoea agglomerans, Geobacillus stearothermophilus, Lysi-nibacillus boronitolerans, Bacillus pumilus, Pseudomonas stutzeri,Pseudomonas xanthomarina, Lysinibacillus fusiformis, Serratialiquefaciens, Serratia liquefaciens, Arthrobacter sp., Enterobacteraerogenes, Escherichia coli, and Citrobacter freundii were found(Tables 4�7) to be present in the corrosion products collectedfrom all of the stations. These bacteria were identified asheterotrophic bacteria, acid producers, iron bacteria, and man-ganese oxidizers.3.3. Chemical Analysis. Table 8 lists the concentrations of

chloride and sulfate in the corrosion products. The chlorideconcentration was in the range between 113 and 382 mg/L,whereas the sulfate concentration was almost nil. The presence ofchloride indicates the possibility of water being present in thecorrosion products. The negligible amount of sulfate and theuniform distribution of oxygen in the flow of the diesel waterinterface estimated in the corrosion products supports theabsence of SRB in the corrosion products. This finding supportsthe previous observations made in Indian pipelines.20,21 The rareoccurrence of SRBmight be due to the stop mode of operation ofthe pipeline, which was neglected in the present study.3.4. Metal Concentration.Table 9 reports the concentrations

of elements in the corrosion products collected from differentstations. The lead content was in the range between 102 and 107mg/kg during the collection in September 2009, whereas inJanuary 2010, it was in the range of 64�95mg/kg. Copper was inthe range of 29�162 mg/kg. The manganese showed a max-imum value of 5650 mg/kg and a minimum of 2030 mg/kg. The

iron content was in the range between 289 750 and 467 800 mg/kg. The chromium was in the range between 13 and 165 mg/kg.The zinc showed a minimum of 0 and a maximum of 473 mg/kg.The trace elements were present in the corrosion product in

the following decreasing order:

Fe >Mn > Zn >Cu > Pb >Cr

Iron and manganese are the major constituents of the corro-sion products. In addition, copper, chromium, zinc, and lead werefound in the corrosion products. Above 95% of the iron contentwas detected and was the same as quantified by magnet (i.e.,separation). This result reveals that iron is the major componentof the corrosion products, which could reduce the lifetime of thepipeline. Wright22 suggested use of a fuel additive consisting oftin, antimony, lead, and mercury, with preferred percentages byweight, apart from impurities, of 60�80 wt % tin, 15�30 wt %antimony, 2�7 wt % lead, and 3�12 wt % mercury. The impactof other trace metals in the pipeline also should be taken intoaccount by the owner of the pipeline. Maruthamuthu et al.23 alsodetected the presence of some trace metals in the corrosionproducts of an aviation turbine fuel transporting pipeline. Furtherinvestigation is needed to find the reason for the presence of tracemetals in the corrosion products.

Table 8. Chloride and Sulfate Concentrations (mg/kg) inCorrosion Products Collected from Different Stations

date of collection station chloride (mg/kg) sulfate (mg/kg)

Sep 24, 2009 1 382 nil

Sep 27, 2009 3 255 nil

Jan 24, 2010 1 153 nil

Jan 26, 2010 2 312 nil

Jan 28, 2010 3 113 nil

Mar 30, 2010 4 115 nil

Table 9. Concentrations (mg/kg) of Trace Elements in theCorrosion Products Collected from Different Stations

date of collection station Pb Cu Mn Fe Cr Zn

Sep 24, 2009 1 107 29 4410 289 750 47 37

Sep 27, 2009 3 102 116 4100 305 400 71 50

Jan 24, 2010 1 95 40 2620 467 800 13 nil

Jan 26, 2010 2 79 162 2030 377 300 60 473

Jan 28, 2010 3 64 98 2570 459 500 26 19

Mar 30, 2010 4 60 62 5650 757 620 165 247

Figure 2. XRD analysis of corrosion product collected from station 3.

Figure 1. XRD analysis of corrosion product collected from station 1.



3.5. XRD Analysis of Corrosion Products. Figures 1 and 2show the details of XRD data corresponding to the phasespresent in the samples collected at stations 1 and 3, respec-tively. Ferric oxide, manganese oxide hydroxide, and ferricchloride were observed in the samples collected at station 1(Figure 1). In the case of station 3, ferric oxide and manganeseoxide hydroxide were observed (Figure 2). This indicates thatthe bacteria accelerate the formation of ferric and manganesecomplexes by the conversion of ferrous and manganese ions inthe corrosion products. The reduction in intensity indicatesthe formation of low-crystallinity nature of the corrosionproducts.

3.6. Infrared Spectroscopy. Figure 3 shows the IR spectrumof corrosion inhibitor (Unicor J) and corrosion productscollected from stations 1, 3, and 4. IR spectrum of UnicorJ (corrosion inhibitor) shows the characteristic band at2855 cm�1 indicating the presence of C—H aliphatic stretching.A peak at 1710 cm�1 indicates the presence of the carbonylgroup. The peaks at 1607, 1505, 1460, and 1378 cm�1 indicatethe presence of carboxylate anion.The IR spectrum of the station 1 corrosion product

(Figure 3a) shows the peaks at 2923 and 2857 cm�1 indicatingthe presence of C—H aliphatic stretching. The broad peak at3396 cm�1 indicates the presence of hydroxyl groups. The peaks

Figure 3. FTIR analysis of corrosion products collected from different stations.



at 1590 and 1457 cm�1 indicate the presence of carboxylateanion. A peak at 1035 cm�1 indicates the presence of C—Obond, and another peak at 885 cm�1 indicates the C—Hmethylgroup. The same peaks were found in the corrosion productsfrom stations 2 and 3. A peak at 573 cm�1 indicates C—Clstretching, which reveals chloride adsorption on the pipeline inthe corrosion products collected from three stations. The pre-sence of carboxylic acid might be due to degradation products ofthe inhibitor or metabolic products of chemolithotrophic andheterotrophic bacteria.3.7. NMR Studies. Figure 4 shows the 1H NMR spectra of

Unicor J and the corrosion products collected from stations 1 and3. 1H NMR spectrum of Unicor J shows a peak in the range of δ9�10 indicating the presence of the carboxylic acid (—COOH)group and another peak in the range of δ 7�8 indicating thepresence of aromatic protons. The peaks in the range of δ 0�3indicate the presence of aliphatic protons. The 1H NMR spectraof corrosion products collected from stations 1 and 3 show peaksin the range of δ 0�3 indicating the presence of aliphaticprotons. A peak at δ 4 indicates the presence of the CH2�Xgroup, where X is an electron-withdrawing group such as Cl orOH. The adsorption of chloride/OH indicates water contamina-tion in the pipeline. There are no peaks in the ranges of δ 7�8and 8�9 as were found in the spectrum of Unicor J. Thisindicates the absence of aromatic protons and —COOH groupfrom the corrosion products, which might be due to degradationof the inhibitor by bacteria or solubility of the inhibitor in water.Figure 5 shows the 13C NMR spectra of Unicor J and the

corrosion products collected from stations 1 and 3. The 13C

NMR spectrum of Unicor J shows a peak at 180 ppm indicatingthe presence of carbonyl carbon (—CdO). The peaks in therange of 0�40 ppm indicate the presence of aliphatic protons,and the peaks in the range of 125�140 ppm indicate the presenceof aromatic protons. The 13C NMR spectra of stations 1 and 3corrosion products showed peaks in the range of 0�40 ppm

Figure 4. 1H NMR analysis of corrosion products collected fromdifferent stations.

Figure 5. 13C NMR analysis of corrosion products collected fromdifferent stations.

Figure 6. Bacterial count in BH medium in the presence of Unicor J.



indicating the presence of aliphatic protons. This reveals that—COOH did not adsorb on the pipeline. Because the inhibitorUnicor J is sparingly soluble in water, it could dissolve at pointscontaining stagnant water in the pipeline. Hence, —COOHgroups could not be detected in the 13C and 1H NMR spectra of

the corrosion products. The number of peaks in the aliphaticregion (0�40 ppm) of the corrosion products collected fromstations 1 and 3was lower than that for Unicor J. It is also possiblethat the bacteria might degrade the adsorbed components ofUnicor J completely.

Figure 7. 1H NMR spectra of Unicor J in the presence and absence of mixed bacterial cultures isolated from different stations.

Figure 8. 13C NMR spectra of Unicor J in the presence and absence of mixed bacterial cultures isolated from different stations.



3.8. Growth of Bacteria in Bushnell and HassMedium.Thetotal viable count of bacteria in the presence of mixed bacterialculture during degradation is presented in Figure 6. Initially, thecount of bacteria was in the range of 102, and it gradually increasedto 108 in the presence of Unicor J. No count was found in presenceof Unicor J without inoculum. This reveals that Unicor J acts as anutrient and encourages the proliferation of bacteria.3.9. Degradation Characterization by NMR Studies.

Figures 7 and 8 show the degradation characterization of Unicor Jin the presence and absence of bacteria. The 1H NMR spectrumof Unicor J without bacteria exhibits an aromatic proton peak atδ 7.6. A peak in the range of δ 2.1�2.3 indicates the presence of amethylene group adjacent to a —COOH group. The peak at δ0.9 indicates the presence of aliphatic methyl (—CH3) protons,and other peaks observed between δ 1.2 and 1.06 indicate thepresence of methylene (—CH2) protons. Because Unicor J issparingly soluble in water (Figure 9), we did not find any sharppeak at δ 10 (—COOH) in the system to which Bushnell andHass (BH) broth had been added. This indicates the solubility ofthe inhibitor in water. In the 1H NMR spectrum of Unicor J withbacteria, some newer peaks (δ 2.20, 2.32, 2.18, and 2.22) couldbe found in the aliphatic proton region as compared to the

uninoculated system. The multiplet observed at δ 2.0�2.4indicates the degradation of inhibitor in the presence bacteria.There is no peak observed at δ 10, indicating the absence ofcarboxylic acid due to bacterial degradation and solubility of—COOH in water. It can be assumed that the carboxylic aciddissolved in contaminated water (broth) was degraded bybacteria. This is why no carboxylic acid was found in thecorrosion products collected in the field by NMR studies.The 13C NMR spectrum of the uninoculated system shows a

peak at 180 ppm indicating the presence of the carboxylic acidgroup. The peaks in the range of 15�35 ppm indicate thepresence of aliphatic protons, and other peaks in the range of125�135 ppm indicate the presence of aromatic protons. The 13

C NMR spectrum of Unicor J in the inoculated system showpeaks in the range of 20�40 ppm indicating the presence ofaliphatic protons, but there are also some new peaks in thatregion indicating the degraded components of Unicor J due tobacterial activity. The peaks in the range of 120�140ppm indicate the presence of aromatic protons. The neweraromatic peaks observed at 129.59 and 120.11 ppm reveal thedegradation of Unicor J. There is no peak at 180 ppm, indicatingthe absence of carboxylic acid due to bacteria degradation. Thisclearly reveals that bacteria degrade the components of Unicor J.It can be concluded that, because Unicor J is sparingly soluble in

Table 10. Evaluation of Various Inhibitors by the Weight Loss Method (May 4, 2010):a San Inhibitor 150 < DCI 6A = SanInhibitor 102 < Unicor J

sample no. systemb weight loss (mg)

corrosion rate

(mmpy)

inhibition

efficiency (%)

1 486.5 mL diesel þ 2% water (8 mL of 200 ppm chloride þ 2 mL of mixed culture)

þ 3.5 mL of drag reducers (7 ppm)c31.9 0.2857 �


þ 3.5 mL of drag reducers (7 ppm) þ 5 mL of 10 ppm DCI 6A

18.5 0.1656 42.00


þ 3.5 mL of drag reducers (7 ppm) þ 5 mL of 10 ppm San inhibitor 102

18.6 0.1665 41.69


þ 3.5 mL of drag reducers (7 ppm) þ 5 mL of 10 ppm San inhibitor 150

12.72 0.1513 60.12


þ 3.5 mL of drag reducer (7 ppm) þ 5 mL of 10 ppm Unicor J

31.4 0.2901 1.56

aWith addition of drag reducers. b Inhibitors highlighted in bold. cControl system.

Figure 10. pH values at various concentrations of Unicor J in water.

Figure 9. Photograph showing the solubility of Unicor J in water.



water, the carboxylic acid dissolves in water and acts as a goodnutrient for bacteria, and this is confirmed by the observationsmade earlier by Rajasekar et al.24

3.10. Selection of Inhibitors by Weight Loss. Table 10reports the evaluation of various inhibitors in the presence ofdrag reducers. The efficiency was evaluated in the presence ofbacteria. The corrosion rate was 0.2857 mmpy in the controlsystem. Upon addition of DCI 6A, the corrosion inhibitionefficiency was about 42%, whereas addition of San 102 and San150 gave inhibition efficiencies of 41.69% and 60.12%, respec-tively. Unicor J gave an efficiency of about 1.56%. Therefore, thefollowing order was found in the evaluation of the inhibitors:

San 150 >DCI6A ¼ San 102 >Unicor J

To find the impact of the dissolved form of Unicor J in dieselalong with water, pHwasmeasured and is presented in Figure 10.The pH of diesel with water (control system) was about 7.3,whereas upon addition of 1000, 3000, 5000, 7000, and 10000mg/L Unicor J in diesel containing water, the pH was 6.03, 4.94,4.58, 4.85, and 4.14, respectively. It can be assumed that, if thediesel transporting pipeline has some stagnant points, the UnicorJ reduces the pH of the water. It can be also assumed that theadsorbed carboxylate ions create a low pH, which opens up anavenue for the proliferation of bacteria on the wall of the pipeline.The relationship among the three bacterial communities is one ofmutualism and syntrophy.12,21 The FTIR results support theexistence of such a relationship among the bacterial commu-nities that was created by the carboxylic acid from the adsorbed

components of Unicor J. Considering the topography of thepipeline (Figure 11), the elevation from station 1 to station 4 wasin the range between 0 and 430 m, with the highest elevation(430 m) at station 3. Hence, the muck quantity was higher atstation 3 when compared to the other stations because of waterstagnation.It can be seen from the overall data presented herein that the

inhibition efficiency of San 150 was found to be about 50�60%for water contaminated with 200 ppm chloride. Hence, this studyreveals that the killing efficiency/degradation is extremely im-portant in the selection of inhibitors for field application becausethese tests will assist operators in the selection of commercialinhibitors that have a higher probability of controlling bacterialactivity. The investigators strongly believe that the selectedinhibitor should work against microbial proliferation in petro-leum transporting pipelines.

4. CONCLUSIONS

Chemolithotrophic bacteria and chloride are the causativefactors in the microbial corrosion of petroleum product trans-porting pipelines. The investigators suggest that water stagnationpoints should be identified in petroleum product transportingpipelines. In addition, the corrosion rate depends on the topo-graphy of the pipeline. The estimated trace metals might beinvolved in the corrosion process, which could reduce thelifetimes of pipelines. The degradation study reveals that UnicorJ acts as a good nutrient and encourages the proliferation ofbacteria at water stagnation points. This present study suggests

Figure 11. Topography of the pipeline route.



that water-soluble inhibitors should be avoided in petroleumproduct transporting pipelines.

’AUTHOR INFORMATION

Corresponding Author*Tel.: þ91-4565-227550. Fax: þ91-4565-227779. E-mail:[email protected].

’REFERENCES

(1) Pant, P. K. Oil Field Corrosion Problems. In Proceedings of the3rd National Corrosion Congress on Corrosion Control; National Corro-sion Council of India (NCCI): Karaikudi, India, 1992; p 17.(2) Muthukumar, N.; Rajasekar, A.; Ponmariappan, S.; Mohanan, S.;

Maruthamuthu, S.; Muralidharan, S.; Subramanian, P.; Palaniswamy, N.;Raghavan, M. Microbiologically influenced corrosion in petroleumproduct pipelines: A review. Indian J. Exp. Biol. 2003, 41, 1012–22.(3) Jana, A. K.; Sahota, S. K.; Dhawan, H. C. Failure analysis of oil

pipeline. Bull. Electrochem. 1999, 15, 262.(4) Samant, A. K.; Anto, P. Failure of Pipelines in Indian Offshore

and Remedial Measures. In Proceedings of the 3rd National CorrosionCongress on Corrosion Control; National Corrosion Council of India(NCCI): Karaikudi, India, 1992; p 188.(5) Bahuguna, S. C. Microbiologically Induced Corrosion in an Oil

Field. In Proceedings of the 3rd National Corrosion Congress on CorrosionControl; National Corrosion Council of India (NCCI): Karaikudi, India,1992; p 234.(6) Pope, D. H.; Alan, M. Some experiences with microbiologically-

influenced corrosion. Mater. Perform. 1995, 23.(7) Kobayashi, H.; Rittman, B. E. Microbial removal of hazardous

organic compounds. Environ. Sci. Technol. 1982, 16, 170–183.(8) Jones, D. A.; Amy, P. S. A thermodynamic interpretation of

microbiologically influenced corrosion. Corrosion 2002, 58, 638–645.(9) Little, B.; Ray, R. A perspective on corrosion inhibition by

biofilms. Corrosion 2002, 58, 424–428.(10) Muthukumar, N.; Mohanan, S.; Maruthamuthu, S.; Subramanian,

P.; Palaniswamy, N.; Raghavan, M. Role of Brucella sp. andGallionella sp. inoil degradation and corrosion. Electrochem. Commun. 2003b, 5, 422–427.(11) Rajasekar, A.; Maruthamuthu, S.; Muthukumar, N.; Mohanan,

S.; Subramanian, P.; Palaniswamy, N. Bacterial degradation of naphthaand its influence on corrosion. Corros. Sci. 2005, 47, 257–271.(12) Maruthamuthu, S.; Mohanan, S.; Rajasekar, A.; Muthukumar,

N.; Ponmarippan, S.; Subramanian, P.; Palaniswamy, N. Role of corro-sion inhibitor on bacterial corrosion in petroleum product pipeline.Indian J. Chem. Technol. 2005, 12, 567–575.(13) Ausubel, F. M.; Brent, R.; Kingston, R. E.; Moore, D. D.;

Seidelman, J. G.; Struhl, K. E. Current Protocols in Molecular Biology;Wiley: New York, 1988.(14) Weisburg, W. G.; Barns, S. M.; Pelletier, D. A.; Lane, D. J. 16S

ribosomal DNA for phylogenetic study. J. Bacteriol. 1991, 173, 697–703.(15) Rajasekar,A.;GaneshBabu,T.;KaruthaPandian, S.;Maruthamuthu,

S.; Palaniswamy, N.; Rajendran, A. Biodegradation and corrosion behaviourof Bacillus cereus ACE4 in diesel transporting pipeline. Corros. Sci. 2007,49, 2694–2710.(16) Muthukumar, N.; Maruthamuthu, S.; Mohanan, S.; Palaniswamy,

N. Influence of an oil soluble inhibitor on microbiologically influencedcorrosion in a diesel transporting pipeline. Biofouling 2007, 23 (6), 395–404.(17) Rajasekar, A.; Ganesh Babu, T.; Maruthamuthu, S.; Karutha

Pandian, S. T.; Mohanan, S.; Palaniswamy, N. Biodegradation andcorrosion behaviour of Serratia marcescens ACE2 isolated from an Indiandiesel-transporting pipeline.World J. Microbiol. Biotechnol. 2007, 23 (8),1065–1074.(18) Papavinasam, S. Evaluation and selection of corrosion inhibi-

tors. In Uhlig’s Corrosion Handbook, 2nd ed.; Revie, R. W., Ed.; Wiley:New York, 2000; p 1169.(19) Treseder, R. S.; Baboian, R.; Munger, C. G. NACE Corrosion

Engineer’s Reference Book; NACE International: Houston, TX, 1991.

(20) Rajasekar, A.; Anandkumar, B.; Maruthamuthu, S.; Ting, Y. P.;Pattanathu Rahman, K. S. M. Characterization of corrosive bacterialconsortia isolated from petroleum-product-transporting pipelines. Appl.Microbiol. Biotechnol. 2010, 85, 1175–1188.

(21) Rajasekar, A.; Ponmariappan, S.; Maruthamuthu, S.; Palaniswamy,N. Bacterial Degradation and Corrosion of Naphtha in TransportingPipeline. Curr. Microbiol. 2007, 55 (5), 374–381.

(22) Ralph, W. Improving the efficiency of fuel combustion with afuel additive comprising tin, antimony, lead and mercury. U.S. Patent5,580,359, 1996.

(23) Maruthamuthu, S.; Ramachandran, S.; Dinesh Kumar, B.;Shatish, V.; Palanichamy, S.; Anand kumar, B.; Subramanian, P.; Sah,S. P.; Anbezhil, A.; Palaniswamy, N. Microbial corrosion in aviationturbine transporting pipeline. J. ASTM Int., in press.

(24) Rajasekar, A.; Maruthamuthu, S.; Ting, Y. P. ElectrochemicalBehavior of Serratia marcescens ACE2 on Carbon Steel API 5L-X60 inOrganic/Aqueous Phase. Ind. Eng. Chem. Res. 2008, 47, 6925–6932.

ie1023707

Documents

process of corrosion

orgiecrmicrobial corrosion

bacterial corrosion

corrosion problem

proliferation of bacteria

petroleum product pipelines

iron bacteria

heterotrophic bacteria