Microbial Corrosion in Petroleum Product Transporting Pipelines

ARTICLE pubs.acs.org/IECR

Microbial Corrosion in Petroleum Product Transporting Pipelines Sundaram Maruthamuthu,*,† Baskaran Dinesh Kumar,† Shanmugavel Ramachandran,† Balakrishnan Anandkumar,‡ Seeni Palanichamy,§ Maruthai Chandrasekaran,† Palani Subramanian,† and Narayanan 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 or indirectly enhance corrosion. Field studies have been carried out by CSIR-CECRI to investigate the corrosion problem in petroleum product transporting pipelines in South India. Although Unicor J inhibitor was added in the pipeline to control corrosion, corrosion products were detected in the pipeline. The present study reveals that the degradation of the inhibitor enhances the proliferation of bacteria, 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 gas industry are generally of the cationic/anionic type and include imidazolines, primary amines, diamines, amino amines, oxyalkylated amines, fatty acids, dimertrimer acids, naphthaneic acid, phosphate esters, and dodecyl benzene sulfonic acids. Organic corrosion inhibitors adsorb on the metal surface and form a complex that inhibits corrosion. Their mechanism of action is to form a persistent monolayer film adsorbed at the metal/solution interface. In recent years, microbiologically influenced corrosion has gained substantial interest and importance.14 The identification of heterotrophic bacteria, iron bacteria, and sulfate-reducing bacteria (SRB) in biofilm consortia indicates the role of particular bacteria in the process of corrosion in pipelines and seawater injection systems.36 It is well-known that bacteria can oxidize a wide variety of chemicals and use them as nutrient sources and enhance the proliferation of bacteria.7,8 Microorganisms influence the corrosion by altering the chemistry at the interface between the metal and the bulk fluid9,10 through biogenic MnO2 deposition, conversion of ferrous to ferric ions, pitting by sulfuric acid production,11 and degradation of corrosion inhibitors.12 In pipelines, hydrocarbon and water stratify at the bottom of the line when the velocity is less than that required to drain the liquids through the pipeline, and hydrocarbon degradation by microbes occurs easily at the liquid interface and enhances corrosion.1012 Recently, the degradation of corrosion inhibitors in petroleum product pipelines in Northwest India and its impact on bacterial corrosion have been investigated.12 In the present study, we consider a cross-country pipeline (API 5LX G 52) in South India that transports petroleum products such as kerosene, petrol, and diesel. This pipeline has intermittent petroleum product delivery with pressure boosting stations at different locations. The length of the pipeline is 680 km. Provisions for the collection of corrosion products are also available at all stations except at the originating station. The muck is pushed out of the pipeline by pigs (cylindrical devices that r 2011 American Chemical Society

move with the flow of oil and clean the pipeline interior). Pigs are introduced into the pipeline in the preceding station and received at the following station. Severe corrosion and microfouling problems are faced in the pipeline, even though a corrosion inhibitor (Unicor J) (4 ppm) was added. The corrosion inhibitor contains unsaturated dimeric fatty-acid-based components. In the present study, the distribution of bacteria, degradation of inhibitor, and selection of inhibitor were studied, and the reasons for corrosion are explained.

2. EXPERIMENTAL MATERIALS AND METHODS 2.1. Sample Collection and Bacterial Enumeration. Corrosion products were collected using sterilized conical flasks at various sites, namely, stations 14, during pipeline pigging. The samples collected were transported in an icebox from various sites to the CECRI Microbiology Laboratory. The collected samples were serially diluted (10-fold) using 9 mL of sterile distilled water blanks, and the samples were plated by the pour plate technique.11 2.2. Identification of Bacteria. Genomic DNA of the bacterial isolates was extracted according to the method of Ausubel et al.13 Amplification of gene-encoding small-subunit rRNA was carried out using eubacterial 16S rDNA primers [forward primer 50 -AGAGTTTGATCCTGGCTCAG-30 (E. coli positions 827) and reverse primer 50 -ACGGCTACCTTGTTACG ACTT-30 (E. coli positions 14941513); Weisburg et al.14]. Polymerase chain reaction (PCR) was performed with 50 μL of a reaction mixture containing 2 μL (10 ng) of DNA as the template, each primer at a concentration of 0.5 μM, 1.5 mM MgCl2, and each deoxynucleoside triphosphate (dNTP) at a concentration of 50 μM, as well as 1 μL of Taq DNA polymerase Received: November 24, 2010 Accepted: May 29, 2011 Revised: May 17, 2011 Published: May 29, 2011 8006

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 (MBI Fermentas). PCR was carried out with a Mastercycler Personal instrument (Eppendorf) using the following program: initial denaturation at 95 °C for 1 min; 40 cycles of denaturation (3 min at 95 °C), annealing (1 min at 55 °C), and extension (2 min at 72 °C); followed by a final extension (at 72 °C for 5 min). The amplified product was purified using GFX PCR DNA and Gel Band Purification kit (Amersham Biosciences) and cloned in pTZ57R/T vector according to the manufacturer’s instruction (InsT/Aclone PCR Product Cloning Kit, MBI Fermentas), and transformants were selected on LB medium containing ampicillin (100 μg/mL) and X-gal (80 μg/mL). DNA sequencing was carried out using ABI PRISM 310 Genetic Analyzer (PE Applied Biosystems). For the sequencing reaction, Big Dye Ready Reaction DyeDeoxy Terminator Cycle Sequencing kit (PerkinElmer) was used. 2.3. Chemical Characterization of Corrosion Products. 2.3.1. Chemical Analysis of Corrosion Products. Five grams of corrosion product was mixed with 50 mL of triply distilled water and sonicated for 1/2 h. After sonication, the samples were filtered, and the filtrates were used for chloride and sulfate analysis. Chloride was estimated by the Mohr method and sulfate by the gravimetric method.11 2.3.2. XRD Analysis. Corrosion product collected during pigging of the pipeline from the various field stations was dried and

crushed to a fine powder and used for XRD analysis to determine the nature of the complex formed on the pipeline in field conditions.15 A computer-controlled XRD system, JEOL model JDX-8030, was used to scan the corrosion products (collected at different IOC pumping stations) between 10° and 85° 2θ with Cu 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 for the analysis of the corrosion products. The spectrum was taken in the mid-IR range of 4004000 cm1 with 16 scan speed. The samples were mixed with spectroscopically pure KBr in the ratio of 1:100, and the pellets were fixed in the sample holder for analysis. 2.3.4. NMR Studies. 1H NMR (Bruker, 400 mHz) analysis was used to detect the protons of the nuclei, and 13C NMR analysis was used to detect the 13C isotope of carbon, whose natural abundance is only 1.1% in the corrosion product. The sample of corrosion product and corrosion inhibitor was dissolved using deutrated chloroform solvent.11 2.4. Biodegradation of Inhibitor. In the present study, commercially available corrosion inhibitor used in petroleum product transporting pipelines was evaluated to determine the nature of the degradation process. The medium used for detecting the corrosion inhibitor degradation process was Bushnell Hass broth (magnesium sulfate, 0.20 g/L; calcium chloride, 0.02 g/L; monopotassium phosphate, 1 g/L; dipotassium phosphate, 1 g/L; ammonium nitrate, 1 g/L; ferric chloride, 0.05 g/L; Hi-Media, Mumbai, India). Three sets of Erlenmeyer flasks were used for the corrosion inhibitor (Unicor J) degradation studies using the selected bacterial strains as was done in previous studies.11,12,16,17 2.5. Corrosion Studies. Corrosion studies were performed using 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 then degreased using trichloroethylene. The corrosion rate was calculated by the equation19

Table 1. Weights of the Corrosion Products Collected at Various Stations

a

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 Jan 26, 2010

1 2

3

Jan 28, 2010

3

>10

Mar 30, 2010

4

a

a

corrosion rate ðmmpyÞ ¼

Negligible.

weight loss ðmgÞ CK area ðin:2 Þ time ðhÞ

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

a

heterotrophic bacteria

iron-oxidizing bacteria

acid producers

manganese oxidizers

sulfate-reducing bacteriaa

3.0 105

5.3 104

3.5 105

2.1 104

station 1 (Sep 24, 2009)

4 105


3.0 10

12 10

6.9 10

1.3 10

1.8 102


2.1 10

24 10

3.5 10

5.4 10

2.4 104

station 3 water (Sep 27, 2009)

9 10

10 10

6 10

4.8 10

1.7 104


10 10

15 10

11 10

5.4 10

2.4 104

6 7

4

4

5

4

4

4

5

6

4

5

2

4

4

5

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

a

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


2.8 106

8.0 104

4.8 105

1.3 105


2 x107

21 104

2.8 104

4.6 105

station 4 (Jan 28, 2010) storage tank water (May 2010)

7.2 105 6 104

12 104 9 104

9 104 5 102

4.8 105 3.8 104

Sulfate-reducing bacteria were not found in the second collection of both API agar plates and API broth. 8007

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

Industrial & Engineering Chemistry Research Table 4. Identification of Different Types of Bacteria from Station 1 Corrosion Product sample no.

sample code

identified isolate

1

AS

Pseudomonas alcaligenes

2 3

AS2 AS4

Pseudomonas stutzeri Klebsiella oxytoca

4

AS5

Bacillus cereus

5

AS6

Pseudomonas acetoxians

ARTICLE

Table 6. Identification of Different Types of Bacteria from Station 3 Corrosion Product sample no.

sample code

1

SHB1

Lysinibacillus fusiformis

2 3

SHB4 SHB5

Pseudomonas stutzeri Serratia liquefaciens

4

SHB4

Pseudomonas stutzeri

5

SHB5

Serratia liquefaciens

Acid Producers

identified isolate

6

SAP1

Arthrobacter sp.

7

SAP2

Enterobacter aerogenes

Manganese Oxidizers

Iron Bacteria 1

TIOB3

identified isolate

Heterotrophic Bacteria

Table 5. Identification of Different Types of Bacteria from Station 2 Corrosion Product sample no.

sample code

Bacillus licheniformis

8

SMN1

Escherichia coli

9

SMN2

Citrobacter freundii

2

TIOB6

Bacillus cereus

3

TIOB5

Lysinibacillus sphaericus

4

TIOB2

Bacillus subtilis

5

THB16

Citrobacter sedlakii

6

THB17

Klebsiella pneumoniae

7

THB13

Citrobacter sp.


Table 7. Identification of Different Types of Bacteria from Station 4 Corrosion Product

TAP7

Bacillus carboniphilus

9

TAP6

Bacillus caldolyticus

10

TAP21

Pantoea agglomerans

11

TAP3

Geobacillus stearothermophilus

TMN8 TMN2

Pseudomonas aeruginosa Lysinibacillus boronitolerans

14

TMN3

Bacillus pumilus

15

TMN4

Pseudomonas stutzeri

16

TMN7

Pseudomonas xanthomarina

MIOB9

Bactericera cockerelli

2

MIOB13

Pseudomonas aeruginosa

3 4

MIOB13 MIOB5

Pseudomonas entomophila Citrobacter sedlakii

5

MHB5

Pseudomonas monteilii

6

MHB4

Pseudomonas putida

7

MHB1

Bacillus cereus

8

MHB4

Pseudomonas luteola

9

MHBC

Bacillus alcalophilus

10 11

MAP3 MAP1

Vibrio sp. Klebsiella pneumoniae

12

MAP2

Vibrio sp.

13

MMN3

Bacillus sp.

14

MMN1

Pseudomonas otitidis

15

MMN3A

Klebsiella pneumoniae

Manganese Oxidizers

3. RESULTS AND DISCUSSION

collected from various stations. The weight of the corrosion product at station 1 was about 3 kg, whereas that at station 3 was above 10 kg. Negligible amounts of corrosion product were obtained at stations 2 and 4. The corrosion products were collected in the sumps by the owner of the pipeline, which does not give the true picture of the actual weight of the corrosion products. The fact that the amount of corrosion product was higher at station 3 might be due to the stop mode of operation of the pipeline. It is strongly believed that the corrosion was higher at station 3 because of water stagnation in the pipeline. 3.2. Enumeration of Microbes. Tables 2 and 3 report the data on the different types of bacteria (heterotrophic bacteria, acid producers, iron bacteria, sulfate-reducing bacteria, and manganese

1

Acid Producers

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

3.1. Weights of Corrosion Products Collected from Various Stations. Table 1 lists the weights of corrosion products

identified isolate


Manganese Oxidizers 12 13

sample code Iron Bacteria

Acid Producers 8

sample no.

oxidizers) enumerated in the corrosion products collected from four different stations during September 2009 and January 2010. The bacterial counts were in the range between 102 and 107 colony forming units (CFU)/g. It can be seen from Tables 2 and 3 that heterotrophic bacteria, acid producers, iron bacteria, sulfate-reducing bacteria, and manganese oxidizers were in the range between 104 and 107 CFU/g. It is also inferred from the data that there was not much of variation in the bacterial counts of all of the samples collected from the different stations. Table 2 shows that the bacterial count of SRB was in the range between 102 and 104 CFU/g when the API agar plate was used. When API broth was used, SRB could not be detected in the first collection in September 2009. In the second collection (Table 3), SRB could not be detected in either API agar or broth. This indicates that the 8008



ARTICLE

Table 8. Chloride and Sulfate Concentrations (mg/kg) in Corrosion Products Collected from Different Stations date of collection

station

chloride (mg/kg)

sulfate (mg/kg)

Sep 24, 2009

1

382

nil

Sep 27, 2009 Jan 24, 2010

3 1

255 153

nil 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 the Corrosion 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 Jan 24, 2010

3 1

102 95

116 40

4100 2620

305 400 467 800

71 13

50 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

influence of SRB on the corrosion of the pipeline is negligible. Tables 47 report the different types of bacteria identified in the corrosion products collected from various stations. Bactericera cockerelli, Pseudomonas aeruginosa, Pseudomonas entomophila, Citrobacter sedlakii, Pseudomonas monteilii, Pseudomonas putida, Bacillus cereus Pseudomonas luteola, Bacillus alcalophilus, Vibrio sp., Klebsiella pneumoniae, Bacillus sp., Pseudomonas otitidis, Bacillus licheniformis, Lysinibacillus sphaericus, Bacillus subtilis, Citrobacter sedlakii, Bacillus carboniphilus, Bacillus caldolyticus, Pantoea agglomerans, Geobacillus stearothermophilus, Lysinibacillus boronitolerans, Bacillus pumilus, Pseudomonas stutzeri, Pseudomonas xanthomarina, Lysinibacillus fusiformis, Serratia liquefaciens, Serratia liquefaciens, Arthrobacter sp., Enterobacter aerogenes, Escherichia coli, and Citrobacter freundii were found (Tables 47) to be present in the corrosion products collected from all of the stations. These bacteria were identified as heterotrophic bacteria, acid producers, iron bacteria, and manganese oxidizers. 3.3. Chemical Analysis. Table 8 lists the concentrations of chloride and sulfate in the corrosion products. The chloride concentration was in the range between 113 and 382 mg/L, whereas the sulfate concentration was almost nil. The presence of chloride indicates the possibility of water being present in the corrosion products. The negligible amount of sulfate and the uniform distribution of oxygen in the flow of the diesel water interface estimated in the corrosion products supports the absence of SRB in the corrosion products. This finding supports the previous observations made in Indian pipelines.20,21 The rare occurrence of SRB might be due to the stop mode of operation of the 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 different stations. The lead content was in the range between 102 and 107 mg/kg during the collection in September 2009, whereas in January 2010, it was in the range of 6495 mg/kg. Copper was in the range of 29162 mg/kg. The manganese showed a maximum value of 5650 mg/kg and a minimum of 2030 mg/kg. The

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

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

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 corrosion products. In addition, copper, chromium, zinc, and lead were found in the corrosion products. Above 95% of the iron content was detected and was the same as quantified by magnet (i.e., separation). This result reveals that iron is the major component of the corrosion products, which could reduce the lifetime of the pipeline. Wright22 suggested use of a fuel additive consisting of tin, antimony, lead, and mercury, with preferred percentages by weight, apart from impurities, of 6080 wt % tin, 1530 wt % antimony, 27 wt % lead, and 312 wt % mercury. The impact of other trace metals in the pipeline also should be taken into account by the owner of the pipeline. Maruthamuthu et al.23 also detected the presence of some trace metals in the corrosion products of an aviation turbine fuel transporting pipeline. Further investigation is needed to find the reason for the presence of trace metals in the corrosion products. 8009



ARTICLE

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

3.5. XRD Analysis of Corrosion Products. Figures 1 and 2 show the details of XRD data corresponding to the phases present in the samples collected at stations 1 and 3, respectively. Ferric oxide, manganese oxide hydroxide, and ferric chloride were observed in the samples collected at station 1 (Figure 1). In the case of station 3, ferric oxide and manganese oxide hydroxide were observed (Figure 2). This indicates that the bacteria accelerate the formation of ferric and manganese complexes by the conversion of ferrous and manganese ions in the corrosion products. The reduction in intensity indicates the formation of low-crystallinity nature of the corrosion products.

3.6. Infrared Spectroscopy. Figure 3 shows the IR spectrum of corrosion inhibitor (Unicor J) and corrosion products collected from stations 1, 3, and 4. IR spectrum of Unicor J (corrosion inhibitor) shows the characteristic band at 2855 cm1 indicating the presence of C—H aliphatic stretching. A peak at 1710 cm1 indicates the presence of the carbonyl group. The peaks at 1607, 1505, 1460, and 1378 cm1 indicate the presence of carboxylate anion. The IR spectrum of the station 1 corrosion product (Figure 3a) shows the peaks at 2923 and 2857 cm1 indicating the presence of C—H aliphatic stretching. The broad peak at 3396 cm1 indicates the presence of hydroxyl groups. The peaks 8010



ARTICLE

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

at 1590 and 1457 cm1 indicate the presence of carboxylate anion. A peak at 1035 cm1 indicates the presence of C—O bond, and another peak at 885 cm1 indicates the C—H methyl group. The same peaks were found in the corrosion products from stations 2 and 3. A peak at 573 cm1 indicates C—Cl stretching, which reveals chloride adsorption on the pipeline in the corrosion products collected from three stations. The presence of carboxylic acid might be due to degradation products of the inhibitor or metabolic products of chemolithotrophic and heterotrophic bacteria. 3.7. NMR Studies. Figure 4 shows the 1H NMR spectra of Unicor J and the corrosion products collected from stations 1 and 3. 1H NMR spectrum of Unicor J shows a peak in the range of δ 910 indicating the presence of the carboxylic acid (—COOH) group and another peak in the range of δ 78 indicating the presence of aromatic protons. The peaks in the range of δ 03 indicate the presence of aliphatic protons. The 1H NMR spectra of corrosion products collected from stations 1 and 3 show peaks in the range of δ 03 indicating the presence of aliphatic protons. A peak at δ 4 indicates the presence of the CH2X group, where X is an electron-withdrawing group such as Cl or OH. The adsorption of chloride/OH indicates water contamination in the pipeline. There are no peaks in the ranges of δ 78 and 89 as were found in the spectrum of Unicor J. This indicates the absence of aromatic protons and —COOH group from the corrosion products, which might be due to degradation of 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

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

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

NMR spectrum of Unicor J shows a peak at 180 ppm indicating the presence of carbonyl carbon (—CdO). The peaks in the range of 040 ppm indicate the presence of aliphatic protons, and the peaks in the range of 125140 ppm indicate the presence of aromatic protons. The 13C NMR spectra of stations 1 and 3 corrosion products showed peaks in the range of 040 ppm 8011



ARTICLE

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

Figure 8.

13

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

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

the corrosion products. The number of peaks in the aliphatic region (040 ppm) of the corrosion products collected from stations 1 and 3 was lower than that for Unicor J. It is also possible that the bacteria might degrade the adsorbed components of Unicor J completely. 8012



ARTICLE

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

inhibition

sample no.

systemb

weight loss (mg)

(mmpy)

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)c

31.9

0.2857

2

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

18.5

0.1656

42.00

18.6

0.1665

41.69

12.72

0.1513

60.12

31.4

0.2901

1.56

þ 3.5 mL of drag reducers (7 ppm) þ 5 mL of 10 ppm DCI 6A 3

481.5 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) þ 5 mL of 10 ppm San inhibitor 102

4

481.5 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) þ 5 mL of 10 ppm San inhibitor 150

5 a

481.5 mL diesel þ 2% water (8 mL of 200 ppm chloride þ 2 mL of mixed culture) þ 3.5 mL of drag reducer (7 ppm) þ 5 mL of 10 ppm Unicor J

With addition of drag reducers. b Inhibitors highlighted in bold. c Control system.

Figure 10. pH values at various concentrations of Unicor J in water. Figure 9. Photograph showing the solubility of Unicor J in water.

3.8. Growth of Bacteria in Bushnell and Hass Medium. The total viable count of bacteria in the presence of mixed bacterial culture during degradation is presented in Figure 6. Initially, the count of bacteria was in the range of 102, and it gradually increased to 108 in the presence of Unicor J. No count was found in presence of Unicor J without inoculum. This reveals that Unicor J acts as a nutrient and encourages the proliferation of bacteria. 3.9. Degradation Characterization by NMR Studies. Figures 7 and 8 show the degradation characterization of Unicor J in the presence and absence of bacteria. The 1H NMR spectrum of Unicor J without bacteria exhibits an aromatic proton peak at δ 7.6. A peak in the range of δ 2.12.3 indicates the presence of a methylene group adjacent to a —COOH group. The peak at δ 0.9 indicates the presence of aliphatic methyl (—CH3) protons, and other peaks observed between δ 1.2 and 1.06 indicate the presence of methylene (—CH2) protons. Because Unicor J is sparingly soluble in water (Figure 9), we did not find any sharp peak at δ 10 (—COOH) in the system to which Bushnell and Hass (BH) broth had been added. This indicates the solubility of the inhibitor in water. In the 1H NMR spectrum of Unicor J with bacteria, some newer peaks (δ 2.20, 2.32, 2.18, and 2.22) could be found in the aliphatic proton region as compared to the

uninoculated system. The multiplet observed at δ 2.02.4 indicates the degradation of inhibitor in the presence bacteria. There is no peak observed at δ 10, indicating the absence of carboxylic acid due to bacterial degradation and solubility of —COOH in water. It can be assumed that the carboxylic acid dissolved in contaminated water (broth) was degraded by bacteria. This is why no carboxylic acid was found in the corrosion 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 acid group. The peaks in the range of 1535 ppm indicate the presence of aliphatic protons, and other peaks in the range of 125135 ppm indicate the presence of aromatic protons. The 13 C NMR spectrum of Unicor J in the inoculated system show peaks in the range of 2040 ppm indicating the presence of aliphatic protons, but there are also some new peaks in that region indicating the degraded components of Unicor J due to bacterial activity. The peaks in the range of 120140 ppm indicate the presence of aromatic protons. The newer aromatic peaks observed at 129.59 and 120.11 ppm reveal the degradation of Unicor J. There is no peak at 180 ppm, indicating the absence of carboxylic acid due to bacteria degradation. This clearly reveals that bacteria degrade the components of Unicor J. It can be concluded that, because Unicor J is sparingly soluble in 8013



ARTICLE

Figure 11. Topography of the pipeline route.

water, the carboxylic acid dissolves in water and acts as a good nutrient for bacteria, and this is confirmed by the observations made earlier by Rajasekar et al.24 3.10. Selection of Inhibitors by Weight Loss. Table 10 reports the evaluation of various inhibitors in the presence of drag reducers. The efficiency was evaluated in the presence of bacteria. The corrosion rate was 0.2857 mmpy in the control system. Upon addition of DCI 6A, the corrosion inhibition efficiency was about 42%, whereas addition of San 102 and San 150 gave inhibition efficiencies of 41.69% and 60.12%, respectively. Unicor J gave an efficiency of about 1.56%. Therefore, the following 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 diesel along with water, pH was measured 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 10000 mg/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 the diesel transporting pipeline has some stagnant points, the Unicor J reduces the pH of the water. It can be also assumed that the adsorbed carboxylate ions create a low pH, which opens up an avenue for the proliferation of bacteria on the wall of the pipeline. The relationship among the three bacterial communities is one of mutualism and syntrophy.12,21 The FTIR results support the existence of such a relationship among the bacterial communities that was created by the carboxylic acid from the adsorbed

components of Unicor J. Considering the topography of the pipeline (Figure 11), the elevation from station 1 to station 4 was in the range between 0 and 430 m, with the highest elevation (430 m) at station 3. Hence, the muck quantity was higher at station 3 when compared to the other stations because of water stagnation. It can be seen from the overall data presented herein that the inhibition efficiency of San 150 was found to be about 5060% for water contaminated with 200 ppm chloride. Hence, this study reveals that the killing efficiency/degradation is extremely important in the selection of inhibitors for field application because these tests will assist operators in the selection of commercial inhibitors that have a higher probability of controlling bacterial activity. The investigators strongly believe that the selected inhibitor should work against microbial proliferation in petroleum transporting pipelines.

4. CONCLUSIONS Chemolithotrophic bacteria and chloride are the causative factors in the microbial corrosion of petroleum product transporting pipelines. The investigators suggest that water stagnation points should be identified in petroleum product transporting pipelines. In addition, the corrosion rate depends on the topography of the pipeline. The estimated trace metals might be involved in the corrosion process, which could reduce the lifetimes of pipelines. The degradation study reveals that Unicor J acts as a good nutrient and encourages the proliferation of bacteria at water stagnation points. This present study suggests 8014


Industrial & Engineering Chemistry Research that water-soluble inhibitors should be avoided in petroleum product 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 the 3rd National Corrosion Congress on Corrosion Control; National Corrosion 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 petroleum product 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 Corrosion Congress 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 Corrosion Control; National Corrosion Council of India (NCCI): Karaikudi, India, 1992; p 234. (6) Pope, D. H.; Alan, M. Some experiences with microbiologicallyinfluenced 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. and Gallionella sp. in oil 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 naphtha and 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 corrosion 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.; Ganesh Babu, T.; Karutha Pandian, S.; Maruthamuthu, S.; Palaniswamy, N.; Rajendran, A. Biodegradation and corrosion behaviour of 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 influenced corrosion 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 and corrosion behaviour of Serratia marcescens ACE2 isolated from an Indian diesel-transporting pipeline. World J. Microbiol. Biotechnol. 2007, 23 (8), 1065–1074. (18) Papavinasam, S. Evaluation and selection of corrosion inhibitors. 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.

ARTICLE

(20) Rajasekar, A.; Anandkumar, B.; Maruthamuthu, S.; Ting, Y. P.; Pattanathu Rahman, K. S. M. Characterization of corrosive bacterial consortia 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 Transporting Pipeline. Curr. Microbiol. 2007, 55 (5), 374–381. (22) Ralph, W. Improving the efficiency of fuel combustion with a fuel additive comprising tin, antimony, lead and mercury. U.S. Patent 5,580,359, 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 aviation turbine transporting pipeline. J. ASTM Int., in press. (24) Rajasekar, A.; Maruthamuthu, S.; Ting, Y. P. Electrochemical Behavior of Serratia marcescens ACE2 on Carbon Steel API 5L-X60 in Organic/Aqueous Phase. Ind. Eng. Chem. Res. 2008, 47, 6925–6932.

8015


Microbial Corrosion in Petroleum Product Transporting Pipelines

Recommend Documents