Corrosion analysis of internal surface of carbon steel natural gas piping.
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
Faculty of Manufacturing Engineering
CORROSION ANALYSIS OF INTERNAL SURFACE OF
CARBON STEEL NATURAL GAS PIPING
Mohd Fuad Bin Ibrahim
Master of Manufacturing Engineering
(Manufacturing System Engineering)
2013
CORROSION ANALYSIS OF INTERNAL SURFACE OF CARBON STEEL
NATURAL GAS PIPING
MOHD FUAD BIN IBRAIDM
A thesis submitted
in fulfillment of the requirements for the degree of Master of Manufacturing
Engineering (Manufacturing System Engineering)
Faculty of Manufacturing Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
2013
ABSTRACT
Oil and gas industry has been contributing as a largest government income and this
industry manage to control corrosion which causing wear failure in gas pipelines and
potentially cause substantial human and economic losses. The objective of this study is
to study the effect of H2 S04 solution concentration electrolyte to corrosion behaviour of
the internal surface of natural gas pipeline by using Tafel Extrapolation Method. This
research starts with sample preparation where the sample from gas pipelines has taken
and cut into 1Omm x 20 mm dimension. This sample has been tested in corrosion test
experiment to collecting and analysing the data gain from Tafel slope analysis, Optical
Microscopy (OM) and Scanning Electron Microscopy (SEM) to perform corrosion rate
and it effect on the surface morphology and microstructure. Due to the result of this
study, it is point out that corrosion rate increase with high concentration of H2 S04 which
presence in natural gas composition. The data can be used to managing the pipelines
effectively and prevention method can be taken in order to extend the life span of the
pipeline.
ABSTRAK
Jndustri minyak dan gas telah menyumbang kepada pendapatan terbesar kerajaan di
mana kegagalan menguruskan industri ini dalam konteks pengawalan kakisan pada
paip gas akan menyebabkan kegagalan dan kerosakan kepada paip gas serta
menyebabkan kerugian yang besar kepada manusia dan ekonomi. Objektif kajian ini
adalah untuk mengkaji kesan kepekatan H 2S04 elektrolit kepada kelakuan atau ciri-ciri
kakisan permukaan dalaman saluran paip gas asli dengan menggunakan kaedah Tafel
ekstrapolasi. Kajian ini bermula dengan penyediaan sampel di mana sampel dari
saluran paip gas telah diambil dan dipotong menjadi kepada dimensi 1Omm x 20 mm.
Sampel ini telah di uji dalam eksperimen ujian kakisan untuk mengumpul dan
menganalisisa data berdasarkan kepada kecerunan lengkung Tafel, menggunakan
'optical microscopy' (OM) dan scanning electron microscopy (SEM) untuk menentukan
kadar hakisan dan kesan ke morfologi permukaan dan mikrostruktur sampel yg di uji
tersebut. Keputusan daripada
kajian ini, ia menunjukkan bahawa kenaikan kadar
kakisan berlaku apabila diuji dengan larutan H2S0 4yg berkepekatan lebih tinggi. Data
hasil daripada kajian yang dijalankan ini boleh digunakan untuk menguruskan paip gas
secara berkesan dan langkah pencegahan boleh diambil untuk memastikan jangka hayat
paip gas dapat ditingkatkan.
11
DEDICATION
Dedicated to my beloved wife, child, father, mother and family, for giving me moral support
and encouragement.
Also, I dedicate this to all my friends, lecturers and colleagues for their advice and motivation
and
special thanks to Dr.Mohd Asyadi 'Azam Bin Mohd Abid for supervising me in completing
this research.
iii
ACKNOWLEDGEMENT
All praises to the Al-Mighty Allah S.W.T, The Merciful and Beneficent for the strength and
blessing throughout the entire time until completion of this Master Project report. Peace be
upon our prophet Muhammad S.A.W, whose has given light to mankind. Firstly, I wish to
express my sincere appreciation to my Master Project supervisor Dr.Mohd Asyadi 'Azam Bin
Mohd Abid for his guidance, counsels, encouragements, and efforts through his advice in
completing this Master Project and to all my colleagues for encouragement, guidance, critics
and friendship. I am also very thankful to all the UTem Lecturers specially Prof. Dr.
Muhamad Razali, Associate Professor Dr. Mohd Rizal bin Salleh, Dr Muhammad bin Minhat,
Encik Ahmad Yushairi, Dr Mohd Nizam, Dr Zuhriah and last but not least Dr Nur Izan
Syahriah Russin for their guidance, advices and motivation. Without their continued support
and interest, this thesis would not have been same as presented here. Lastly my fellow
postgraduate students should also be recognized for their support. My sincere appreciation
also extends to all my colleagues and others who have provided assistance at various
occasions. Their views and tips are useful indeed.
IV
DECLARATION
I declare that this thesis entitle "Corrosion Analysis of Internal Surface of Carbon Steel
Natural Gas Piping" is the result of my own research except as cited in the references. The
thesis has not been accepted for any degree and is not concurrently submitted in candidature
of any other degree.
.. . . . .4 . . . . . . .
Signature
Name
.ｾＮＬ＠
Date
ＭＴｾＯＷＰＮＺＳ＠
.................
/.: ........................... .
v
'E:::!:P.. ｾＧＺＡＮＯ＠
ＡＷＮｾＧＱＯｴ＠
m
APPROVAL
This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a partial
fulfilment of the requirements for the degree of Master of Manufacturing Engineering
(Manufacturing Systems Engineering). The member of supervisory committee is as follow:
ﾷｾＺ＠
ｾＧＭＰ＠
.....
Dr.Mohd Asyadi 'Azam Bin Mohd Abid
Pensyarah Kanan
Fakulti Kejuruteraan Pembuatan,
Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya,
76100 Durian Tunggal, Melaka, Malaysia.
Vl
TABLE OF CONTENT
Page
ABSTRACT
i
ABSTRAK
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
DECLARATION
v
APPROVAL
vi
TABLE OF CONTENT
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF ABBREVIATIONS
xiii
CHAPTER
1.
2.
INTRODUCTION
1
1.1
Background of Study
1
1.2
Problem Statement
2
1.3
Objective
5
1.4
Scope of Project
5
LITERATURE REVIEW
7
2.1
Introduction
7
2.2
Corrosion in oil and gas
8
2.3
Electrochemical corrosion of iron
10
2.4
Mechanism of corrosion
11
Vll
3.
4.
2.5
Types of corrosion in oil and gas pipeline
13
2.6
Effect of pH to internal pipeline Corrosion
17
2.7
petroleum pipeline
18
2.7.1
Pipeline steel
18
2.7.2
Type of pipeline
19
2.7.3
Carbon steel pipeline
21
2.8
Corrosion Expression
21
2.9
Tafel Extrapolation method
24
2.10 Optical Microscopy
25
2.11 Scanning Electron microscopy
25
METHODOLOGY
26
3.1
Experiment procedures
26
3.2
Sample preparation
27
3.2.1
Sample cutting
29
3.2.2
Mounting
30
3.2.3
Grinding and Polishing
31
3.2.4
Etching
32
3.3
Natural Gas composition
33
3.4
Microscopic Structure Analysis : SEM
33
3.5
Electrolyte for corrosion rate measurement
34
3.6
Corrosion rate measurement: Tafel extrapolation method
35
RESULT AND DISCUSSION
4.1
39
Observation and presentation of the collected data
vm
39
4.2
Tafel Extrapolation method
39
4.3
Morphological analysis of the corroded tested sample of pipeline
44
4.4
5.
4.3.1
Microstructure observation of steel sample before corrosion test
44
4.3.2
Microstructure observation of steel sample after corrosion test
45
Representative SEM analysis of corroded pipeline sample
47
CONCLUSION AND RECOMMENDATIONS
55
5.1
Conclusion
55
5.2
Recommendation
56
REFERENCE/BIBLIOGRAPHY
57
IX
LIST OF TABLES
TABLE
PAGE
TITLE
2.1
Failures in oil and gas industry
9
2.3
Line pipe physical properties
20
3.1
Material specification
28
3.4
Natural Gas Composition
33
4.1
The value of corrosion rate, Icom and Ecorr for different concentrations of H2S04. 41
4.2
Corroded surface composition percentages of element in corrosion product
x
53
LIST OF FIGURES
FIGURE
PAGE
TITLE
1.1
Corrosion in the internal pipeline
2
2.1
Simple corrosion cell
7
2.2
Step involved in corrosion
10
2.3
The corrosion process
11
2.4
Internal Pitting corrosion in pipeline
14
2.5
Erosion corrosion at pipe elbow
15
2.6
Co2 corrosion on internal pipe surface
16
2.7
H2S corrosion on internal pipe surface
17
3.1
Flow of methodology process
27
3.2
Pipeline sample
28
3.3
Sample preparation flow chart.
29
3.4
Sample cutting using EDM wire cut machine
30
3.5
Sample dimensions
30
3.6
Casing for cold mounting process
31
3.7
Mounted specimen
31
3.8
Sample grinding using IMPTECH 20 V
32
3.9
Equipment setup for SEM
34
3.10
Example of Tafel plot
36
XI
3.1 l(a) The equipment setup for Tafel Extrapolation
37
3.1 l(b)Corrosion cell kit (CCK) with Gamry Instrument
38
4.1
The setup of the corrosion experiment connected with Gamry Instrument
40
4.2
Tafel curve obtained once the corrosion film is formed on tested sample in 1 M H2S04
41
4.3
Tafel curve obtained once the corrosion film is formed on tested sample in0.50 M H2S04
42
4.4
Tafel curve obtained once the corrosion film is formed on tested sample in 0.1 M H2S04
43
4.5
Tafel curve obtained once the corrosion film is formed on tested sample in 0.01 M H2S0 4
43
4.6
Optical micrograph for the microstructure of API X65 carbon steel pipe for 10 x magnification
45
4.7
Optical micrograph for the microstructure of API X65 carbon steel pipe for 10 x magnification
45
4.8
Optical micrograph of pitting corrosion after corrosion test
47
4.9
SEM morphology image of sample in the solution of 1.0 M H2 S04
48
4.10
Cross - section SEM image show the thickness of corrosion layer after corrosion test with 1.0 M H 2S04 •
49
4.11
SEM morphology image of sample in the solution of 0.5 M H2 S04
50
4.12
SEM morphology image of sample in the solution ofO.l M H2S04
50
4.13
Cross - section SEM image show the thickness of corrosion layer after corrosion test with 0.5 M H2 S04
51
4.14
Cross - section SEM image show the thickness of corrosion layer after corrosion test with 0.1 M H 2S04
51
4.15
Peak of elements present in the corrosion product after corrosion test with 1.0 M H 2S04
53
LIST OF ABBREVIATIONS
WEDM
Electro discharge machine
sec
Stress Cracking Corrosion
Ksi
kilopound per square inch
SEM
Scanning Electron Microscope
EDX
Energy Dispersion X-Ray
XRD
X-Ray Diffraction
OM
Optical Microscopy
µm
Micrometer
xm
CHAPTERl
INTRODUCTION
1.1 Background of the study
Oil and Gas industry has been contributing as a largest government income and
Petronas is the role player in this industry and it is evolving from year to year due to world
population growth. Malaysia has the 25th largest oil reserve and 14th largest gas reserve in the
world (Razalli, 2005). Downstream have different players, and a more diverse range of
interests. In oil refining, there are Petronas Penapisan (with plants in Terengganu and Melaka),
Shell, ExxonMobil and Conoco. Petronas Gas and Manufacturers of Liquidized Natural Gas
(MLNG) are involved in gas processing and transmission. Gas distribution is handled by Gas
Malaysia. Oil and Gas sector is expected to generate RM 131.4 billion in Gross National
Income by 2020 (5% annual growth) in the period from 2010 to 2020.Twelve entry points
projects (EPPs) have been identified under the oil, gas and energy sector.
Due to its unique requirements, the industry has developed standards and practices in
order to make sure this industry remain competitive and sustainable. Many of these standards
and practices such as the selection of materials, quality assurance and control in construction,
non-destructive testing, corrosion and welding practices will probably find their way and tries
to meet the ever demanding public expectations. This study is focusing on corrosion as one of
the standards that gives a huge impact in company's cost and profit. Corrosion represents a
tremendous economic loss and much can be done to reduce it. As the 14th largest gas reserve
1
in the world, gas industry has also grown significantly. Globalize all over the world, pipelines
are the most common and feasible medium in transporting natural gas because of the volume
that can be transported. Pipeline normally is constructed by metal which is related to defect
such as corrosion. Figure 1.1 shows the corrosion impact of internal pipeline.
Figure 1.1 : Corrosion in the internal pipeline
Corrosion may appear in different forms, such as general corrosion with the uniform
loss of the wall thickness or pitting corrosion, which corresponds to the local wall thickness
reduction. To avoid failures and meet the safety requirement standard, corrosion must be
detected, measured and the remaining strength of the corroded area has to be determined.
1.2 Problem statement
Pipeline systems are the most effective medium to transport Oil and Gas (O&G)
product such as natural gas from one location to another location, offshore to onshore and
from transmission to the distribution until it meets the consumer in a mass scale. Pipelines
ability and reliability are based on their material properties and its composition may reach the
weakness point due to certain factors such as condition and environment of the internal
pipelines surface. In order to maintain the life span of a pipeline, such a big amount of money
should be invested in maintenance and preventive area. External surface of pipeline is not a
2
major issue during maintenance process as compared to the internal surface of the pipelines.
The hard it goes the more it costs.
In the mix scenario of the world economy environment force the reduction of cost and
eliminate unnecessary expenses. Oil and gas sector also is no exception influenced by the
economy crisis and most of the cost is involved in corrosion. The total annual cost of
corrosion in the oil and gas production industry alone is estimated to be $1.3 billion, including
$589 million in surface pipeline and facility costs, $463 million in downhole tubing expenses
and $320 million in capital expenditure related to corrosion.
Ｈｓｴｯｲ･ｾ＠
2012). Corrosion is the
main threat to the petroleum industry depending on the depth, length, orientation and possible
future growth of the defect.
As the infrastructure of industrialized countries continues to age, more and more
failures due to corrosion are occurring. Replacing all the bridges and pipelines (gas, oil, water)
would be prohibitively expensive, and unnecessary as most are in good condition and can
provide many more years of service. Figuring out which ones are failing and how long they
can last is the function of service life prediction. (Kelly, 2006). In order to restructure the cost,
an understanding of how the pipeline will corrode is important and preventive action can be
taken. Corrosion attacks almost every component, as all metals and alloys are subjected to it.
Carbon steel is a material that widely used in Oil and Gas (0 & G) industrial units because of
its low cost and excellent mechanical properties and it also faces severe attack from corrosion
failure.
However, to fully understand this phenomenon a detailed study of chemical, physical
and mechanical properties of material is required. The internal corrosion is preferred to be
concerned in this project because the sulphur contain in the natural gas is one of the corrosive
agent that can attack the pipeline surface. The internal corrosion rate of carbon steel pipelines
3
varies in a complex way with the gas composition specifically carbon dioxide (C02), 0 2 and
hydrogen sulphide (H2S) with presence of condensed water chemistry. The effect of the
corrosion process which produce a corrosion product which deposited on the internal pipeline
gas. Corrosion product forms a scales layer and act as a protective barrier to prevent the
corrosion on the pipeline surface. This scales layer will grown at the certain thickness and
become brittle. This characteristic will exposed this layer for easily removed by a mechanical
force from the gases flow.
The area of the removed scales layer will expose to the corrosion process and can
develops localized pits due to the pitting corrosion. This process of corrosion wills week
mechanical properties the area of exposing until the final failure. The understanding of this
phenomenon can be demonstrated by testing the internal natural gas pipeline corrosion sample
with simulated solution as identified as a major contributor to corrosion failuere and the data
can be used to predict the corrosion behaviour in oil and gas industries.
Quantitative understanding of the corrosion rate of steel under these conditions will be
a key point to an accurate risk assessment of pipelines from internal corrosion. The finding of
the study helps in constructing pipelines with higher resistance to corrosion using suitable
methods such as coating and etc. Yet, according to NACE, the international corrosion society,
if oil and gas production firms manage corrosion effectively, they can improve compliance
with safety, health and environmental policies, increase plant availability, and reduce leaks,
deferment costs and the amount of unplanned maintenance. (Storck, 2012)
4
1.3 Objective
The aims of this research are:
1.
To study on the effect of solution concentration of H2S04 electrolyte to corrosion
behaviour of internal surface of natural gas pipeline using Tafel Extrapolation Method.
11.
To investigate morphology of corroded piping sample of the different solution
concentration of H2S04.
1.4 Scope
In order to achieve the objectives, this research is focusing on the following scopes:
For objective i:
i.
Tested the natural gas piping samples with 1 M, 0.5 M, 0.1 M and 0.01 M of
H2S04 solution.
ii.
Immersed the sample in H2S04 solution and tested using Gamry Instrument.
m.
Collected the data of corrosion rate, corrosion potential (Ecorr) and corrosion
current Ocorr) from sample of natural gas corrosion surface with different effects
of H2S04 solution of electrolyte using Tafel Extrapolation Method.
For objective ii:
i.
Observe and magnify the surface morphology of untested sample and tested
sample using Optical Microscopy (OM).
ii.
Representative SEM analysis of plane view and cross sectional view of the
tested sample.
iii.
Compare the finding from OM and SEM of the different concentration of
H2S04.
5
iv.
Conclude the corrosion behaviour of the natural gas piping samples from the
result analysis.
6
Chapter2
Literature Review
2.1 Introduction
There are so many studies on corrosion and it has a similar definition that describes the
meaning of corrosion. Corrosion is defined as the destruction or deterioration of a material
because of reaction with its environment (Fontana, 1986). Corrosion is the degradation of
materials' properties due to interactions with their environments, and corrosion of most metals
(and many materials for that matter) is inevitable. (Kelly, 2006).
Corrosion of metals could be considered as extractive metallurgy in reverse where it is
concerned primarily with the winning of the metal from the ore and refining or alloying the
metal for use. (Fontana,1986). Thus from the definition of corrosion, corrosion processes are
the process where the metal atoms are removed from the surface and it leads to weakening of
the structure, meet the resistance limits and finally causes failures to the metal. Figure 2.1
expresses simple process in sample of corroding cell.
Cumtnt Path (External) ---
+ -
"The Corrosion Battery" (Ready to Discharge)
Figure 2.1 : Simple corrosion cell
7
Most corrosion processes involve at least two electrochemical reactions (one anodic and one
cathodic). A corroding surface as shown in figure 2.1 can be thought of as a short-circuited
battery; the dissolution reaction at the anode supplies electrons for the reduction reaction at the
cathode. A short circuit is the electrical connection made by a conductor between the two
physical sites, which are often separated by very small distances. (Kelly,2006).
2.2 Corrosion in Oil and Gas industry
According to (Papavinasam, 2006), the oil and gas industry uses large quantities of
carbon and low-alloy steels in the construction of pipelines, offshore rigs and structures Global
energy needs led to extend searches for oil in offshore environments. Since then offshore
pipelines have become the unique means of efficiently transporting hydrocarbons from
offshore installations. As mentioned in problem statement, carbon steel is and still remains the
primary member in the construction of oil and gas transport pipelines owing to economic
reasons, availability and well developed technology (L.Fosbol, 2009).
However, its downside is the fact that it easily corrodes, changing to its more
thermodynamically stable form (iron ore) thus becoming mechanically unreliable. Corrosion
protection is therefore very important because of the large sums of money spent on corrosion
mitigation designs, repair of corroded pipes, refurbishment and cleaning of polluted
environments. During this process the metal atoms are removed from the surface, which leads
to structure weakening and finally failures. Corrosion attacks almost every component, as all
metals and alloys are subjected to it. It can appear down hole or above the ground, on internal
and external surfaces, destroying the equipment and interrupting the processes.
8
Corrosion is the main threat to the petroleum industry. Its enormous impact is shown
in Table 2.1. The values in the table may be assumed as average ones, because they vary
regarding to the country and region e.g. in Western Europe corrosion-related failures come to
25%, in the Gulf of Mexico and Poland about 50%, while in India they reach 80%
(Samant,2003).
Table 2.1 : Failures in oil and gas industry (from Kennanl and Harrop,2003)
Frequency [%)
Type of failure
I
I
Corrosion (aU types)
33
Fatigue
18
Mechanical damage/overload
14
Brittle fracture
9
Fabrication defects (excluding welding defects)
Welding defects
Others
I
I
9
7
10
On the other hand, the study of corrosion in the oil and gas industry usually involved
the sweet (C02) and sour (H2S) corrosion. These types of corrosion are famous in oil and gas
pipelines. But these corrosions caused by gas during the transportation of crude oil in the
pipelines. However, a very few studies mention that the corrosion is caused by crude oil. This
study is carried out to determined whether the corrosion in the pipelines also affected by the
crude oil.
9
Faculty of Manufacturing Engineering
CORROSION ANALYSIS OF INTERNAL SURFACE OF
CARBON STEEL NATURAL GAS PIPING
Mohd Fuad Bin Ibrahim
Master of Manufacturing Engineering
(Manufacturing System Engineering)
2013
CORROSION ANALYSIS OF INTERNAL SURFACE OF CARBON STEEL
NATURAL GAS PIPING
MOHD FUAD BIN IBRAIDM
A thesis submitted
in fulfillment of the requirements for the degree of Master of Manufacturing
Engineering (Manufacturing System Engineering)
Faculty of Manufacturing Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
2013
ABSTRACT
Oil and gas industry has been contributing as a largest government income and this
industry manage to control corrosion which causing wear failure in gas pipelines and
potentially cause substantial human and economic losses. The objective of this study is
to study the effect of H2 S04 solution concentration electrolyte to corrosion behaviour of
the internal surface of natural gas pipeline by using Tafel Extrapolation Method. This
research starts with sample preparation where the sample from gas pipelines has taken
and cut into 1Omm x 20 mm dimension. This sample has been tested in corrosion test
experiment to collecting and analysing the data gain from Tafel slope analysis, Optical
Microscopy (OM) and Scanning Electron Microscopy (SEM) to perform corrosion rate
and it effect on the surface morphology and microstructure. Due to the result of this
study, it is point out that corrosion rate increase with high concentration of H2 S04 which
presence in natural gas composition. The data can be used to managing the pipelines
effectively and prevention method can be taken in order to extend the life span of the
pipeline.
ABSTRAK
Jndustri minyak dan gas telah menyumbang kepada pendapatan terbesar kerajaan di
mana kegagalan menguruskan industri ini dalam konteks pengawalan kakisan pada
paip gas akan menyebabkan kegagalan dan kerosakan kepada paip gas serta
menyebabkan kerugian yang besar kepada manusia dan ekonomi. Objektif kajian ini
adalah untuk mengkaji kesan kepekatan H 2S04 elektrolit kepada kelakuan atau ciri-ciri
kakisan permukaan dalaman saluran paip gas asli dengan menggunakan kaedah Tafel
ekstrapolasi. Kajian ini bermula dengan penyediaan sampel di mana sampel dari
saluran paip gas telah diambil dan dipotong menjadi kepada dimensi 1Omm x 20 mm.
Sampel ini telah di uji dalam eksperimen ujian kakisan untuk mengumpul dan
menganalisisa data berdasarkan kepada kecerunan lengkung Tafel, menggunakan
'optical microscopy' (OM) dan scanning electron microscopy (SEM) untuk menentukan
kadar hakisan dan kesan ke morfologi permukaan dan mikrostruktur sampel yg di uji
tersebut. Keputusan daripada
kajian ini, ia menunjukkan bahawa kenaikan kadar
kakisan berlaku apabila diuji dengan larutan H2S0 4yg berkepekatan lebih tinggi. Data
hasil daripada kajian yang dijalankan ini boleh digunakan untuk menguruskan paip gas
secara berkesan dan langkah pencegahan boleh diambil untuk memastikan jangka hayat
paip gas dapat ditingkatkan.
11
DEDICATION
Dedicated to my beloved wife, child, father, mother and family, for giving me moral support
and encouragement.
Also, I dedicate this to all my friends, lecturers and colleagues for their advice and motivation
and
special thanks to Dr.Mohd Asyadi 'Azam Bin Mohd Abid for supervising me in completing
this research.
iii
ACKNOWLEDGEMENT
All praises to the Al-Mighty Allah S.W.T, The Merciful and Beneficent for the strength and
blessing throughout the entire time until completion of this Master Project report. Peace be
upon our prophet Muhammad S.A.W, whose has given light to mankind. Firstly, I wish to
express my sincere appreciation to my Master Project supervisor Dr.Mohd Asyadi 'Azam Bin
Mohd Abid for his guidance, counsels, encouragements, and efforts through his advice in
completing this Master Project and to all my colleagues for encouragement, guidance, critics
and friendship. I am also very thankful to all the UTem Lecturers specially Prof. Dr.
Muhamad Razali, Associate Professor Dr. Mohd Rizal bin Salleh, Dr Muhammad bin Minhat,
Encik Ahmad Yushairi, Dr Mohd Nizam, Dr Zuhriah and last but not least Dr Nur Izan
Syahriah Russin for their guidance, advices and motivation. Without their continued support
and interest, this thesis would not have been same as presented here. Lastly my fellow
postgraduate students should also be recognized for their support. My sincere appreciation
also extends to all my colleagues and others who have provided assistance at various
occasions. Their views and tips are useful indeed.
IV
DECLARATION
I declare that this thesis entitle "Corrosion Analysis of Internal Surface of Carbon Steel
Natural Gas Piping" is the result of my own research except as cited in the references. The
thesis has not been accepted for any degree and is not concurrently submitted in candidature
of any other degree.
.. . . . .4 . . . . . . .
Signature
Name
.ｾＮＬ＠
Date
ＭＴｾＯＷＰＮＺＳ＠
.................
/.: ........................... .
v
'E:::!:P.. ｾＧＺＡＮＯ＠
ＡＷＮｾＧＱＯｴ＠
m
APPROVAL
This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a partial
fulfilment of the requirements for the degree of Master of Manufacturing Engineering
(Manufacturing Systems Engineering). The member of supervisory committee is as follow:
ﾷｾＺ＠
ｾＧＭＰ＠
.....
Dr.Mohd Asyadi 'Azam Bin Mohd Abid
Pensyarah Kanan
Fakulti Kejuruteraan Pembuatan,
Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya,
76100 Durian Tunggal, Melaka, Malaysia.
Vl
TABLE OF CONTENT
Page
ABSTRACT
i
ABSTRAK
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
DECLARATION
v
APPROVAL
vi
TABLE OF CONTENT
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF ABBREVIATIONS
xiii
CHAPTER
1.
2.
INTRODUCTION
1
1.1
Background of Study
1
1.2
Problem Statement
2
1.3
Objective
5
1.4
Scope of Project
5
LITERATURE REVIEW
7
2.1
Introduction
7
2.2
Corrosion in oil and gas
8
2.3
Electrochemical corrosion of iron
10
2.4
Mechanism of corrosion
11
Vll
3.
4.
2.5
Types of corrosion in oil and gas pipeline
13
2.6
Effect of pH to internal pipeline Corrosion
17
2.7
petroleum pipeline
18
2.7.1
Pipeline steel
18
2.7.2
Type of pipeline
19
2.7.3
Carbon steel pipeline
21
2.8
Corrosion Expression
21
2.9
Tafel Extrapolation method
24
2.10 Optical Microscopy
25
2.11 Scanning Electron microscopy
25
METHODOLOGY
26
3.1
Experiment procedures
26
3.2
Sample preparation
27
3.2.1
Sample cutting
29
3.2.2
Mounting
30
3.2.3
Grinding and Polishing
31
3.2.4
Etching
32
3.3
Natural Gas composition
33
3.4
Microscopic Structure Analysis : SEM
33
3.5
Electrolyte for corrosion rate measurement
34
3.6
Corrosion rate measurement: Tafel extrapolation method
35
RESULT AND DISCUSSION
4.1
39
Observation and presentation of the collected data
vm
39
4.2
Tafel Extrapolation method
39
4.3
Morphological analysis of the corroded tested sample of pipeline
44
4.4
5.
4.3.1
Microstructure observation of steel sample before corrosion test
44
4.3.2
Microstructure observation of steel sample after corrosion test
45
Representative SEM analysis of corroded pipeline sample
47
CONCLUSION AND RECOMMENDATIONS
55
5.1
Conclusion
55
5.2
Recommendation
56
REFERENCE/BIBLIOGRAPHY
57
IX
LIST OF TABLES
TABLE
PAGE
TITLE
2.1
Failures in oil and gas industry
9
2.3
Line pipe physical properties
20
3.1
Material specification
28
3.4
Natural Gas Composition
33
4.1
The value of corrosion rate, Icom and Ecorr for different concentrations of H2S04. 41
4.2
Corroded surface composition percentages of element in corrosion product
x
53
LIST OF FIGURES
FIGURE
PAGE
TITLE
1.1
Corrosion in the internal pipeline
2
2.1
Simple corrosion cell
7
2.2
Step involved in corrosion
10
2.3
The corrosion process
11
2.4
Internal Pitting corrosion in pipeline
14
2.5
Erosion corrosion at pipe elbow
15
2.6
Co2 corrosion on internal pipe surface
16
2.7
H2S corrosion on internal pipe surface
17
3.1
Flow of methodology process
27
3.2
Pipeline sample
28
3.3
Sample preparation flow chart.
29
3.4
Sample cutting using EDM wire cut machine
30
3.5
Sample dimensions
30
3.6
Casing for cold mounting process
31
3.7
Mounted specimen
31
3.8
Sample grinding using IMPTECH 20 V
32
3.9
Equipment setup for SEM
34
3.10
Example of Tafel plot
36
XI
3.1 l(a) The equipment setup for Tafel Extrapolation
37
3.1 l(b)Corrosion cell kit (CCK) with Gamry Instrument
38
4.1
The setup of the corrosion experiment connected with Gamry Instrument
40
4.2
Tafel curve obtained once the corrosion film is formed on tested sample in 1 M H2S04
41
4.3
Tafel curve obtained once the corrosion film is formed on tested sample in0.50 M H2S04
42
4.4
Tafel curve obtained once the corrosion film is formed on tested sample in 0.1 M H2S04
43
4.5
Tafel curve obtained once the corrosion film is formed on tested sample in 0.01 M H2S0 4
43
4.6
Optical micrograph for the microstructure of API X65 carbon steel pipe for 10 x magnification
45
4.7
Optical micrograph for the microstructure of API X65 carbon steel pipe for 10 x magnification
45
4.8
Optical micrograph of pitting corrosion after corrosion test
47
4.9
SEM morphology image of sample in the solution of 1.0 M H2 S04
48
4.10
Cross - section SEM image show the thickness of corrosion layer after corrosion test with 1.0 M H 2S04 •
49
4.11
SEM morphology image of sample in the solution of 0.5 M H2 S04
50
4.12
SEM morphology image of sample in the solution ofO.l M H2S04
50
4.13
Cross - section SEM image show the thickness of corrosion layer after corrosion test with 0.5 M H2 S04
51
4.14
Cross - section SEM image show the thickness of corrosion layer after corrosion test with 0.1 M H 2S04
51
4.15
Peak of elements present in the corrosion product after corrosion test with 1.0 M H 2S04
53
LIST OF ABBREVIATIONS
WEDM
Electro discharge machine
sec
Stress Cracking Corrosion
Ksi
kilopound per square inch
SEM
Scanning Electron Microscope
EDX
Energy Dispersion X-Ray
XRD
X-Ray Diffraction
OM
Optical Microscopy
µm
Micrometer
xm
CHAPTERl
INTRODUCTION
1.1 Background of the study
Oil and Gas industry has been contributing as a largest government income and
Petronas is the role player in this industry and it is evolving from year to year due to world
population growth. Malaysia has the 25th largest oil reserve and 14th largest gas reserve in the
world (Razalli, 2005). Downstream have different players, and a more diverse range of
interests. In oil refining, there are Petronas Penapisan (with plants in Terengganu and Melaka),
Shell, ExxonMobil and Conoco. Petronas Gas and Manufacturers of Liquidized Natural Gas
(MLNG) are involved in gas processing and transmission. Gas distribution is handled by Gas
Malaysia. Oil and Gas sector is expected to generate RM 131.4 billion in Gross National
Income by 2020 (5% annual growth) in the period from 2010 to 2020.Twelve entry points
projects (EPPs) have been identified under the oil, gas and energy sector.
Due to its unique requirements, the industry has developed standards and practices in
order to make sure this industry remain competitive and sustainable. Many of these standards
and practices such as the selection of materials, quality assurance and control in construction,
non-destructive testing, corrosion and welding practices will probably find their way and tries
to meet the ever demanding public expectations. This study is focusing on corrosion as one of
the standards that gives a huge impact in company's cost and profit. Corrosion represents a
tremendous economic loss and much can be done to reduce it. As the 14th largest gas reserve
1
in the world, gas industry has also grown significantly. Globalize all over the world, pipelines
are the most common and feasible medium in transporting natural gas because of the volume
that can be transported. Pipeline normally is constructed by metal which is related to defect
such as corrosion. Figure 1.1 shows the corrosion impact of internal pipeline.
Figure 1.1 : Corrosion in the internal pipeline
Corrosion may appear in different forms, such as general corrosion with the uniform
loss of the wall thickness or pitting corrosion, which corresponds to the local wall thickness
reduction. To avoid failures and meet the safety requirement standard, corrosion must be
detected, measured and the remaining strength of the corroded area has to be determined.
1.2 Problem statement
Pipeline systems are the most effective medium to transport Oil and Gas (O&G)
product such as natural gas from one location to another location, offshore to onshore and
from transmission to the distribution until it meets the consumer in a mass scale. Pipelines
ability and reliability are based on their material properties and its composition may reach the
weakness point due to certain factors such as condition and environment of the internal
pipelines surface. In order to maintain the life span of a pipeline, such a big amount of money
should be invested in maintenance and preventive area. External surface of pipeline is not a
2
major issue during maintenance process as compared to the internal surface of the pipelines.
The hard it goes the more it costs.
In the mix scenario of the world economy environment force the reduction of cost and
eliminate unnecessary expenses. Oil and gas sector also is no exception influenced by the
economy crisis and most of the cost is involved in corrosion. The total annual cost of
corrosion in the oil and gas production industry alone is estimated to be $1.3 billion, including
$589 million in surface pipeline and facility costs, $463 million in downhole tubing expenses
and $320 million in capital expenditure related to corrosion.
Ｈｓｴｯｲ･ｾ＠
2012). Corrosion is the
main threat to the petroleum industry depending on the depth, length, orientation and possible
future growth of the defect.
As the infrastructure of industrialized countries continues to age, more and more
failures due to corrosion are occurring. Replacing all the bridges and pipelines (gas, oil, water)
would be prohibitively expensive, and unnecessary as most are in good condition and can
provide many more years of service. Figuring out which ones are failing and how long they
can last is the function of service life prediction. (Kelly, 2006). In order to restructure the cost,
an understanding of how the pipeline will corrode is important and preventive action can be
taken. Corrosion attacks almost every component, as all metals and alloys are subjected to it.
Carbon steel is a material that widely used in Oil and Gas (0 & G) industrial units because of
its low cost and excellent mechanical properties and it also faces severe attack from corrosion
failure.
However, to fully understand this phenomenon a detailed study of chemical, physical
and mechanical properties of material is required. The internal corrosion is preferred to be
concerned in this project because the sulphur contain in the natural gas is one of the corrosive
agent that can attack the pipeline surface. The internal corrosion rate of carbon steel pipelines
3
varies in a complex way with the gas composition specifically carbon dioxide (C02), 0 2 and
hydrogen sulphide (H2S) with presence of condensed water chemistry. The effect of the
corrosion process which produce a corrosion product which deposited on the internal pipeline
gas. Corrosion product forms a scales layer and act as a protective barrier to prevent the
corrosion on the pipeline surface. This scales layer will grown at the certain thickness and
become brittle. This characteristic will exposed this layer for easily removed by a mechanical
force from the gases flow.
The area of the removed scales layer will expose to the corrosion process and can
develops localized pits due to the pitting corrosion. This process of corrosion wills week
mechanical properties the area of exposing until the final failure. The understanding of this
phenomenon can be demonstrated by testing the internal natural gas pipeline corrosion sample
with simulated solution as identified as a major contributor to corrosion failuere and the data
can be used to predict the corrosion behaviour in oil and gas industries.
Quantitative understanding of the corrosion rate of steel under these conditions will be
a key point to an accurate risk assessment of pipelines from internal corrosion. The finding of
the study helps in constructing pipelines with higher resistance to corrosion using suitable
methods such as coating and etc. Yet, according to NACE, the international corrosion society,
if oil and gas production firms manage corrosion effectively, they can improve compliance
with safety, health and environmental policies, increase plant availability, and reduce leaks,
deferment costs and the amount of unplanned maintenance. (Storck, 2012)
4
1.3 Objective
The aims of this research are:
1.
To study on the effect of solution concentration of H2S04 electrolyte to corrosion
behaviour of internal surface of natural gas pipeline using Tafel Extrapolation Method.
11.
To investigate morphology of corroded piping sample of the different solution
concentration of H2S04.
1.4 Scope
In order to achieve the objectives, this research is focusing on the following scopes:
For objective i:
i.
Tested the natural gas piping samples with 1 M, 0.5 M, 0.1 M and 0.01 M of
H2S04 solution.
ii.
Immersed the sample in H2S04 solution and tested using Gamry Instrument.
m.
Collected the data of corrosion rate, corrosion potential (Ecorr) and corrosion
current Ocorr) from sample of natural gas corrosion surface with different effects
of H2S04 solution of electrolyte using Tafel Extrapolation Method.
For objective ii:
i.
Observe and magnify the surface morphology of untested sample and tested
sample using Optical Microscopy (OM).
ii.
Representative SEM analysis of plane view and cross sectional view of the
tested sample.
iii.
Compare the finding from OM and SEM of the different concentration of
H2S04.
5
iv.
Conclude the corrosion behaviour of the natural gas piping samples from the
result analysis.
6
Chapter2
Literature Review
2.1 Introduction
There are so many studies on corrosion and it has a similar definition that describes the
meaning of corrosion. Corrosion is defined as the destruction or deterioration of a material
because of reaction with its environment (Fontana, 1986). Corrosion is the degradation of
materials' properties due to interactions with their environments, and corrosion of most metals
(and many materials for that matter) is inevitable. (Kelly, 2006).
Corrosion of metals could be considered as extractive metallurgy in reverse where it is
concerned primarily with the winning of the metal from the ore and refining or alloying the
metal for use. (Fontana,1986). Thus from the definition of corrosion, corrosion processes are
the process where the metal atoms are removed from the surface and it leads to weakening of
the structure, meet the resistance limits and finally causes failures to the metal. Figure 2.1
expresses simple process in sample of corroding cell.
Cumtnt Path (External) ---
+ -
"The Corrosion Battery" (Ready to Discharge)
Figure 2.1 : Simple corrosion cell
7
Most corrosion processes involve at least two electrochemical reactions (one anodic and one
cathodic). A corroding surface as shown in figure 2.1 can be thought of as a short-circuited
battery; the dissolution reaction at the anode supplies electrons for the reduction reaction at the
cathode. A short circuit is the electrical connection made by a conductor between the two
physical sites, which are often separated by very small distances. (Kelly,2006).
2.2 Corrosion in Oil and Gas industry
According to (Papavinasam, 2006), the oil and gas industry uses large quantities of
carbon and low-alloy steels in the construction of pipelines, offshore rigs and structures Global
energy needs led to extend searches for oil in offshore environments. Since then offshore
pipelines have become the unique means of efficiently transporting hydrocarbons from
offshore installations. As mentioned in problem statement, carbon steel is and still remains the
primary member in the construction of oil and gas transport pipelines owing to economic
reasons, availability and well developed technology (L.Fosbol, 2009).
However, its downside is the fact that it easily corrodes, changing to its more
thermodynamically stable form (iron ore) thus becoming mechanically unreliable. Corrosion
protection is therefore very important because of the large sums of money spent on corrosion
mitigation designs, repair of corroded pipes, refurbishment and cleaning of polluted
environments. During this process the metal atoms are removed from the surface, which leads
to structure weakening and finally failures. Corrosion attacks almost every component, as all
metals and alloys are subjected to it. It can appear down hole or above the ground, on internal
and external surfaces, destroying the equipment and interrupting the processes.
8
Corrosion is the main threat to the petroleum industry. Its enormous impact is shown
in Table 2.1. The values in the table may be assumed as average ones, because they vary
regarding to the country and region e.g. in Western Europe corrosion-related failures come to
25%, in the Gulf of Mexico and Poland about 50%, while in India they reach 80%
(Samant,2003).
Table 2.1 : Failures in oil and gas industry (from Kennanl and Harrop,2003)
Frequency [%)
Type of failure
I
I
Corrosion (aU types)
33
Fatigue
18
Mechanical damage/overload
14
Brittle fracture
9
Fabrication defects (excluding welding defects)
Welding defects
Others
I
I
9
7
10
On the other hand, the study of corrosion in the oil and gas industry usually involved
the sweet (C02) and sour (H2S) corrosion. These types of corrosion are famous in oil and gas
pipelines. But these corrosions caused by gas during the transportation of crude oil in the
pipelines. However, a very few studies mention that the corrosion is caused by crude oil. This
study is carried out to determined whether the corrosion in the pipelines also affected by the
crude oil.
9