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Procedia Engineering 152 (2016) 247 – 250
International Conference on Oil and Gas Engineering, OGE-2016
Analysis of corrosion defects on oil pipeline surface using scanning
electron microscopy and soil thionic and sulfate-reducing bacteria
quantification
Chesnokova M.G.a,b*, Shalaj V.V.a, Kraus Y.A.a, Cherkashina N.V.a, Mironov A.Yu.c
b
a
Omsk State Technical University, 11, Mira Pr., Omsk 644050, Russian Federation
Omsk State Medical University of Ministry of Healthcare of the Russian Federation, Omsk, 12, Lenin str., Omsk 644099, Russian Federation
c
FBUN Moscow Research Institute of Epidemiology and Microbiology. GN Gabrichevskogo Rospotrebnadzor,10, Admiral Makarov str.,
Moscow- 125212, Russian Federation
Abstract
We completed an analysis of corrosion defects on oil pipeline surface by instrumentality of scanning electron microscopy and
identified soil thionic and sulfate-reducing bacteria quantity. A surface of samples was studied by using of raster electron
microscopy as a preparation for qualitative and quantitative analysis of elemental composition. Was identified a quantity of
sulfate-reducing and thionic bacteria in a samples of soil contiguous to the surface of underground oil pipelines in the of KhantyMansiysk autonomous region territory (Ugra). A result of this research shows a significant oxidative activity, which accompanied
an expressed corrosion process. Microbiological analysis of soil shows an existence of thionic bacteria and an absence of sulfatereducing bacteria. Microorganisms existed in soil induces the corrosion of pipeline steel. Using of scanning electron microscopy
in a combination with finding of quantitative specification of thionic and sulfate-reducing bacteria in soils allows to study the
nature of corrosive surface of the oil pipelines and to evaluate an extension degree of biocorrosion in complex.
©2016
2016The
TheAuthors.
Authors.
Published
Elsevier
©
Published
by by
Elsevier
Ltd.Ltd.
This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the Omsk State Technical University.
Peer-review under responsibility of the Omsk State Technical University
Keywords: biocorrosion activity of oil pipeline soil; scanning electron microscopy; sulfate-reducing bacteria; thiobacteria
* Corresponding author. Tel.: +7-903-927-6695; fax: 7-381-265-2349.
E-mail address: [email protected]
1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the Omsk State Technical University
doi:10.1016/j.proeng.2016.07.698
248
M.G. Chesnokova et al. / Procedia Engineering 152 (2016) 247 – 250
1. Introduction
Corrosion processes on a surface of metals depends of physical- chemical conditions in a subsurface layer. An
intensity of corrosion process is under influence of pH index, oxygen concentration, oxidative- reducing potential
and chemical compounds concentration [1, 2]. Sulfate- reducing bacteria which responsible for 70- 80% of
biodamage reduces sulfates existed in soil with an oxygen production used for cathodic depolarization process.
Hydrogen sulfide decreases a hydrogen overstrain in acidic and acescent soil, eases a cathodic process passing.
Sulfide- ions accelerates an anodic process [3]. All of this leads to corrosion current intensification and promotes a
dissolution process acceleration. Thionic bacteria in their vital activity process forms an insoluble iron hydroxide
film (FeOH)3, which leads to differential aeration macrocorrosion pairs forming. It promotes a localization and
metal dissolution process acceleration [4].
Goals of research were to conduct an analysis of oil pipeline corrosion defects using a scanning electron
microscopy, to determine soil thionic and sulfate-reducing bacteria quantity.
2. Study subject
An ultimate examination of soil including scanning electron microscopy in combination with soil thionic and
sulfate- reducing bacteria quantitative feature determination allows to study an oil pipelines corrosive surface and to
evaluate a biocorrosion progress level. A pipe samples corrosive surface examination using the raster electron
microscope JEOL JCM-5700 with energy dispersive spectrometer for realization of qualitative and quantitative
elemental analysis allows to determine carbon and oxygen high quantity testifying significant oxidative activity
during the corrosive process. Soil microbiological analysis showed thionic bacteria existence and an absence of
sulfate- reducing bacteria. Received data are necessary for prevention of biocorrosion and for protection methods
development.
3. Methods
As a preparation to research we took a samples of pipes clipped from an oil pipeline during maintenance works.
Before the microscopic examination of pipeline steel samples they were subjected to eddy current control using
eddy current flaw detector (VD-1) for corrosion sites diagnostics. A samples surface was studied by using a raster
electron microscope JEOL JCM-5700 with energy dispersive spectrometer for qualitative and quantitative elemental
composition analysis. We identified a sulfate-reducing and thionic bacteria quantity in soil samples contiguous to
underground oil pipeline surface in the Khanty- Mansiysk autonomous region territory (Ugra). Soil samples for
microbiological analysis were taken in an amount of 25±5 g and converted into suspension. Sulfate-reducing and
thionic bacteria quantity was determined by serial tenfold dilutions method. For sulfate-reducing bacteria cultivation
a sterile Postgate's substratum was used. A test-tubes with a sterile substratum were used as a control samples to
standardize an examinations. An amounts of microbial cells were determined in 1ml of suspension and in 1g of soil
sample. For authotrophic thionic bacteria cultivation a seeding was produced in a test- tubes with Beyerinck's
substratum. Bacteria quantity is calculated in colony forming unit (CFU) per 1g of soil. Biometric analysis was
carried out by toolkits STATISTICA-6 and BIOSTATISTICS using, and by dint of Microsoft Excel responsibilities.
In all statistic analysis procedures values critical level p was assumed to be 0.05, herewith a “p” indexes were
ranked in 3 levels of statistically significant differences: р<0.05; р<0.01; р<0.001. Allocation normality check was
conducted by Shapiro- Wilk's test using. Fischer's F-criterion was used for general variances equality hypotheses
testing. Quantitative attributes average sample values are present in the text as M±SE (M- an average sample, SEstandard average error).
4. Results and discussion
Corrosive destructions in microscopic level may be formed in zones of microorganisms accumulation.
Microorganisms presented in soil stimulates a pipeline steel corrosion. To study the nature and composition of
M.G. Chesnokova et al. / Procedia Engineering 152 (2016) 247 – 250
corrosive defects formed on a pipeline samples surface was used a raster electron microscope JEOL JCM-5700 with
energy dispersive spectrometer (Fig.1).
Fig.1. Microfotography of surface of pipeline's sample. Composition in atomic fractions, %: С- 34.03, О- 46.20, Na-3.05, Si- 1.62, Ca – 2.57,
Fe-12.52.
An external layer was
high carbon and oxygen
process. Microbiological
thiobacteria existence in
bacteria.
a greyish-brown rust consisting of hydrated iron (III) oxides (Fe2O3•H2O). Determined
levels indicates a significant oxidative activity accompanied by pronounced corrosive
soil analysis aimed at bacteriological sulfate- reducing bacteria identifying showed
concentration M±m (lоg) 3.75±0.1 per 1g of soil and an absence of sulfate-reducing
Quantity of thionic bacteria in an oil pipeline soil
9000
8000
7000
6000
5000
4000
3000
2000
average
average±standard error
1000
0
average ±1.96 *
standard error
Сontrol
Soil pipeline
Fig. 2. Quantity of thionic bacteria in oil pipeline soil. (axis X- control sample, pipeline soil; axis Y- concentration of thionic bacteria (M) per 1 g of
soil (CFU/g - colony forming unit).
Fig.2. demonstrates microbiological examination features of oil pipeline soil samples in different survey points.
In soil samples of 10m from pipeline (control) thionic bacteria quantity was (М) 624.10 CFU/g, (Ме) 500.00 CFU/g,
(Р25%-Р75%) 300.00- 690.00 CFU/g. It is higher than their concentration in soil samples gotten by oil pipeline
trenching by higher, lower and side pipeline generatrices (М) 5738.75 CFU/g, (Ме) 3 800.00 CFU/g, (Р25%-Р75%)
1361.00-7691.00 CFU/g (Т=5.00, Z=4.59, p<0.0001). Thiobacillus genus microorganisms are accelerating steel
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M.G. Chesnokova et al. / Procedia Engineering 152 (2016) 247 – 250
corrosion process and final oxidation products are sulfates and sulfuric acid, that decreases an environment pH
index. So, scanning electron microscopy using in accompany with soil thionic and sulfate- reducing bacteria
quantitative specifications determination enabled to study oil pipelines corrosive surface morphology and
composition and to evaluate biocorrosion progress level. Received data are necessary for biocorrosion controlling
and prevention, for protection methods development and for oil pipeline track rational choice [5,6].
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