The effect of seawater on the corrosion behavior of natural gas pipelines in Malaysia.
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
Faculty of Manufacturing Engineering
THE EFFECT OF SEAWATER ON THE CORROSION
BEHAVIOR OF NATURAL GAS PIPELINES IN
MALAYSIA
Suziee Binti Sukarti
Master of Manufacturing Engineering
2013
THE EFFECT OF SEAWATER ON THE CORROSION
BEHAVIOR OF NATURAL GAS PIPELINES IN
MALAYSIA
SUZIEE BINTI SUKARTI
A thesis submitted
In fulfillment of the requirement for the degree of Master of Manufacturing
Engineering (Manufacturing System Engineering) in Manufacturing Engineering
Faculty of Manufacturing Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
2013
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
(Manufacturing System Engineering). The member of supervisory committee is as follow:
Dr Mohd Asyadi 'Azam Bin Mohd Abid
DECLARATION
I declare that this thesis entitle "The Effect of Seawater On The Corrosion Behavior
Of Natural Gas Pipelines In Malaysia" 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.
Signature
Name
Date
SUZIEE BINTI SUKARTI
DEDICATION
To my beloved parents, Sukarti bin Sukimi and Siti Masrah binti Yusoff, all my friends.
Thank you for the continuous support and encouragement.
ABSTRAK
Air laut ialah kimia yang agresif secara semulajadi, cecair yang kompleks yang memberi
kesan kepada hampir semua struktur bahan pada tahap tertentu. Kakisan dalam air laut
adalah bergantung kepada beberapa faktor seperti komposisi bahan, sifat kimia air, pH,
biofouling, organisma mikrobiologi, pencemaran dan suhu. Pemahaman terhadap faktor
yang memuerikesankepada karatan di dalam air laut dapat membantu rekabentuk bahan,
komponen dan sistem untuk pengggunaan optimum dan hayat struktur bahan. Satu kajian
telah dijalankan untuk mengkaji kesan perbezaan air laut di sekitar Semenanjung
Malaysia ke atas keluli karbon yang berfungsi sebagai saluran paip bqgipetroleum dan
gas asli. -Kaedah Extrapolasi Tafel telah dtguna/a:ur-bagi menilai kadar karatan keluli
karbon dengan menggunakan air laut yang berbeza sebagai eletrolit. Dalam eksperimen
ini, keluli karbon AP! 5L X42 telah digunakan dan air laut yang diambil adalah dari Laut
China Se Iatan dan Laut Se/at Me/aka. Se lain pengiraan kadar kakisllfTjenis karatan juga
telah dibincangkan berdasarkan morfologi asas dan kandungan air laut jJ1ga ditentukan.
Didapati bahawa kadar kakisan spesimen keluli karbon adalah leblh noble di Se/at
}..Jelaka-Lautdaripada itu di L-aut China -Selatan. -variasi keputusan diperolehi iaitu
diantara 0. 10 -0. 25 mm I tahun. Karatan jenis seragam dan setempat didapati menyerang
permukaan spesimen dengan teruk. Kadar hakisan yang lebih rendah dicapai dengan
kandungan natrium klorida dan pH yang lebih tinggi. Sebahagian daripada bahan yang
larut seperti oksida ferum juga menyumbang pada pembentukan karat. Secara umumnya,
Laut China Selatan adalah lebih baik bagi penggunaan bahan ini walaupun bahan ini
boleh digunakan di kedua-dua jenis laut.
ABSTRACT
Seawater is inherently chemically aggressive, complex fluid that affects nearly all
structural materials to some extent. Corrosion in the seawater is dependent on a number of
factors such as material composition, water chemistry, pH, biofouling, microbiological
organisms, pollution and contamination and temperature. Understanding how these factors
may affect corrosion in seawater can support the design of materials, components, and
systems for optimal service performance and structural life. A study was taken to
investigate the effect of different seawater surrounding Peninsular Malaysia on the carbon
steel having app1ication as petroleum/natural gas pipeline. The Tafel Extrapolation
technique has been applied to evaluate the corrosion rate of the carbon steel and different
locations of natural seawater have been used as the electrolyte solution. In this experiment,
Carbon steel API SL X42 were utilized and the seawater is taken from the South China Sea
and Strait of Malacca. Beside the corrosion rate calculating the type of corrosion attack has
also been discussed on the basis of the morphology and the content properties of seawater
are determined. It is found that the corrosion rate of the carbon steel --specimen is
Sea 1han 1:hat in the-south China Sea. The
significantly nobler· in-the-Strait ｯｦｾＱ｡ｬ｣＠
results varied from 0.01 to 0.025 mm/year. Immersion test of two hours and ten days were
carried out to determine the corrosion product that formed at the surface of pipe. Localized
corrosion (pitting) and uniform corrosion attacked the surface specimen severely for each
sea. The lower corrosion rate is achieved with higher contents of sodimn chloride and
salinity. Some of the dissolved material such as Iron oxide also distributes to the formation
-0f cfilmsion. -Gencrally;---from--the resuit, -soulh -ch.ina Sea is more favorable in the
application-ef-trns-materiai-even theugh the material is-aGCeptahle in both seas.
ii
ACKNOWLEDGEMENT
First and foremost i offer my sincerest gratitude to my PSM supervisor, Dr. Mohd Asyadi
'Azam Bin Mohd Abid for the advice and guidance. Besides, i would like to thank my
parents, family, friends, lecturers, laboratory technicians and UteM staffs. Finally, i am
really grateful to Universiti Teknikal Malaysia (UTeM), especially to faculty of
Manufacturing Engineering (FKP) for providing me with all the knowledge.
iii
TABLE OF CONTENT
PAGE
APPROVAL
DECLARATION
DEDICATION
ABSTRAK
ABSTRACT
ACKNOWLEDGEMENT
LIST OF TABLES
LIST OF FIGURES
LIST OF ABBREVIATIONS
LIST OF APPENDICES
ll
m
VI
vu
IX
x
OIAPTER
1: INTRODUCTION
1. 0
1.2
1.3
1.4
1.4
1.5
1.6
1
2
3
4
4
5
5
Introduction
Problem statement
Summaries of problem statement
Expected Results
Significant of studies
Objective
Scopes
2: LITERATURE REVIEW
2. 0 Introduction
2.1 Types of Corrosion
2.1. l External Corrosion in the Undersea
2.1.2 Formation of Corrosion With Seawater as Electrol)te
2.2 Undersea Corrosion Mechanism
2.3 Offshore-Oil and Gas Piping
2.3 .1 Grades of Pipelines
2.4 Seawater Surrounding Malaysia
2.5 Environmental Influence on Corrosion
2.5.1 The Effect of Temperature, Salinity, Oxygen and pH on Marine Corrosion
2.6 Electrochemistry Techniques for Corrosion
2.6.1 Electrochemical measurement
2.6.2 Corrosion Surface Analysis
2.6.2. l Stereomicroscope
2.6.2.2 Optical Microscope
2.6.2.3 Differences Between OM and Stereomicroscope
2. 7 Seawater Content Measurement
2.7.1 Spectrophotometer
2.7.1 Incubator
iv
7
7
9
9
11
12
13
14
15
16
16
17
18
18
19
19
20
20
20
2.7.3
21
Multiprobe
3: RESEARCH METHODOLOGY
3 .1 Seawater Location
3.2 Seawater Content Analysis
3.2.1 Spectrophotometer HACH DR2700
3.2.2 Multiprobe YSI Professional Plus
3.2.3 UV Lamp and Binder Incubator BD115
3 .3 Material Selection
3.4 Material Sample Preparation
3.5 Experimental Study
3.5.1 Extrapolation Corrosion Test
3.5.2 Corrosion Surface Analysis
3 .5. 3 Immersion Test
24
26
26
29
29
31
32
34
34
36
37
4: RESULTS AND DISCUSSIONS
4.1
4.2
4. 3
4. 4
4.5
4.6
Observation on Immersion Test
4 .1.1
Microstructure Morphology of Corrosion Product
Seawater Contents
4.2.1 Turbidity, pH and Salinity Result
4.2.2 Seawater Microorganism
4.2.3 Heavy Metal Solution in Seawater
Electrochemical Analysis
Corrosion Rate Analysis
Seawater Content after the Electrochemical Testing
4.5.1 Iron, Manganese and Aluminum Effect
Surface Corrosion Product after Electrochemical Testing
38
40
42
43
44
45
46
50
51
52
56
5: CONCLUSIONS AND RECOMMENDATIONS
5 .1
5 .2
58
Conclusions
Recommendations
59
60
REFERENCES
APPENDICES
64
v
LIST OF TABLES
TABLE
TITLE
PAGE
2.1
Line pipe physical properties
13
3.1
Pipe Sample Properties
20
3.2
Sample Preparation
20
3.3
Seawater locations in Peninsular Malaysia
22
3.4
Specification of Gambry Reference 600
24
3.5
Parameters and reagents
25
4.1
Parameter Value for Seawater Using Multiprobe
43
4.2
E. coli as Microorganism in the Seawater
44
4.3
Metal Solution Value
45
4.4
Seawater Contents for Peninsular Malaysia
46
4.5
Tafel Curves
47
4.6
Corrosion Potential and Corrosion Rate Values
48
4.7
Total anodic current, corrosion current density, corrosion potential and corrosion
4.8
penetration rate.
51
Contents of Seawater after the Corrosion Test
52
vi
LIST OF FIGURES
FIGURE
2. 1
TITLE
PAGE
Electrochemical Reaction Occurring During Corrosion of
Iron Metal in solution condition
2.2
8
Differential corrosion cell by differences in soils. Arrow indicates
direction of ionic and electronic current flow
10
2.3
Average Sea Temperature
14
3.1
Methodology Flowchart
18
3.2
API 5 L X42 Pipes
19
3.3
Water Quality Monitoring Station.
22
3.4
Experimental Setup for Reference 600
23
3.5
Experiment to determine the Manganese
26
3.6
Experiment Equipment (A) Spectrophotometer (B) Binder Incubator
26
4.1
Schematic Illustration oflmmersion Test
39
4.2
(a) Example Observations on Two Hours Immersion,
(b) Example Observation on 10 Days Immersion
39
4.3
Illustration oflmmersion Test after 10 Days
40
4.4
Straits of Malacca Corrosion Products after 10 Days oflmmersion
40
(a) N. Sembilan (b) Johor (c) Melaka.
4.5
Straits of Malacca Corrosion Products after 10 Days oflmmersion
(a) Terengganu (b) Kelantan (c) Pahang.
4.6
41
Magnified Observation on Corrosion Product Using OM
(a) 20µm (b) 50µm for API 5L X42 and (c) Microstructure Comparison
41
4.7
Magnified Observation on API 5L X42 pipe when it's dried
42
4.8
Straits of Malacca Tafel Extrapolation Graph
46
4.9
South China Sea Tafel Extrapolation Graph
47
vii
4.10
Seawater Surrounding Peninsular Malysia Tafel Extrapolation Graph
4.11
(a), (b) and (c) Differences of Seawater Content before and after Tafel
49
Experiment
53
4.12
Iron Hydroxide formed at the surface of the pipe
55
4.13
Seawater after Electrochemical Test
56
4.14
Uniform Surfaces and Pitting Corrosion Attack on the Surface of Carbon Steel
56
4.15
Optical Microscope Magnifications on Pitting and Uniform Corrosion
57
viii
LIST OF ABBREVIATIONS
API
American Petroleum Institute
ASTM
American Society for Testing and Materials
ASME
American Society of Mechanical Engineers
A
Ampere
K
Kelvin
Kg
Kilogram
mis
Meter per second
MIC
Microbiologically Influenced Corrosion
Mpa
Mega pascal
Mm
Milileters
pH
Potential of Hydrogen
sec
Stress Corrosion Cracking
TDS
Total Dissolved Solid
µm
Micronmeter
Fe
Ferum
w
Hidrogen Ion
Mn
Manganese
Al
Aluminium
P.P.T
Part per Thousand
N.T.U
Nephelometric Turbidity Units
ix
LIST OF APPENDICES
PAGE
TITLE
APPENDIX
Peninsular Malaysia: Marine Monitoring Location
43
B
Metal Galvanic Series in Seawater
44
c
Galvanic Corrosion Chart
45
D
Carbon Steel Content
46
E
ASTMG102
47
F
ASTMGl
54
A
x
CHAPTERl
INTRODUCTION
This section basically is an introduction to pipelines underneath seawater in
Malaysia and problem statement for this research. The graphic illustrations can be found in
the appendices.
1.0
Introduction
In recent years, since the first oil pipelines are embedded underneath sea using
welded steel, the most common basic purpose of pipelines underneath sea still remains the
same as the network for the fuel (oil/gas) transportation. The first cross-country pipeline
is called PLUTO (Pipe Line under the Ocean) which is built during the World War II,
since then the technology has improved, the undersea pipeline is a practical ways to
transport water, fuel, oil and gases, therefore carbon steel or are commonly used.
Malaysia also has many companies that develop undersea oil and gas pipelines
that have the capability to design, build, operate and maintain gas processing and
transmission pipeline infrastructure around peninsular and east Malaysia. Natural energy
problem, including environmental aspects had changed the character of pipelines
underneath sea water. According to Institute of Engineering Malaysia (2003), Malaysia
warm seawater is threatened by direct and indirect pollution sources. These changes that
occurred undersea will lead to the pipeline corrosion and simultaneously have a tendency
to degrade. Sea water corrosion involves reactions where the metal surface is transformed
into metal oxides or hydroxides (like rust) (NDV, 2004). Apart from the natural energy
1
problem and environmental changes, the rate of seawater corrosion depends on several
factors like metal impurities, temperature, oxygen access, metallic contact (conductive)
with dissimilar metals, sea water flow velocities, type of metals, surface protection and
stresses.
Failure of submarine pipeline by corrosion has been a familiar phenomenon in
processing plants resulting in unscheduled plants shut down, in consequences; there are
heavy losses in industrial production and disruptions to civil amenities. A lot of research
has been made to overcome the problem with underwater pipeline and its repair still
remained a challenge.
1.1
Problem Statement
Corrosion is an electrochemical process which is the dissolution of the pipeline in
the anodic areas as charged positive ions into the seawater or sea bed sediment. These
ferrous ions react to form oxides and hydroxide and may form ferric salts if the water is
well oxygenated. Palmer (2008) suggests that pipelines buried undersea ought to be an at
least risk of corrosion because of the oxygen content should be low but the offshore
pipelines become often acceptors of corrosion attack, which is enhanced by undersea
biochemical factors. The concentration of salts in the environment and the local
temperature affects the resistivity and pH value, hence, both the potential corrosiveness of
the environment and the coating degradation behavior.
In addition if the seawater has the presence of high chloride or low sulfate levels
then the pipelines are at higher than normal risk of corrosion as the corrosion products of
iron will be more soluble. The activity of the sulfate reducing bacteria also alters with
salinity and temperature. Salinity changes occur in shallow inshore waters in hot and warm
climates (e.g. The south east of Arabian Gulf and Malaysia). A small change in this one of
2
the parameters will change the corrosion rate considerably and when the corrosion
products are not deposited on the steel surface, a very high corrosion rate of several
millimeters per year can occur. (Nyborg, 2005).
The undersea corrosion issue is of great interest for organizations managing
offshore networks for oil/gas transportation. Oil and gas supply companies, engineering
consultants and inspection agents, pay a lot of money to cope with marine corrosion,
developing inspection methods and prevention technologies to enhance the integrity of
undersea pipelines. For example, PETRONAS has undertaken collaborative development
with the Commonwealth Scientific & Industrial Research Organization (CSIRO) to
develop a novel composite prepreg for use in underwater repair of pipelines, with the
solution to be known as PIPEASSURE (Petronas, 2011). Knowledge acquisition from
corrosion literature and expertise for marine facilities integrity management has been the
focus of the research. Thus, knowledge based expert systems are designed and
implemented by modifying computational methods and tools, which are mainly applied in
investigating the industrial system failure. The effects of the corrosive action are metal
loss, reduction of mechanical strength and thereof premature aging of the pipe segments.
1.2
Summary of Problem Statement
The problem can be summarized in three critical points:1.
Influence of seawater on the corrosion piping is apparent nonetheless limited
information exists on the variation of seawater effect on external pipeline
corrosion surrounding Peninsular Malaysia
11.
The variation of seawater characteristic that keep changing due to several factors
such as contaminations might present a different potential corrosion risk and
variable rate of corrosion that can give major on safety, environmental
3
preservation and the economics pipeline operation.
11 1.
The undersea pipeline corrosion is enduring studies that keep varying due to
several factors of seawater variation environment.
1.3
Expected Findings
This particular study can give a better understanding of corrosion behavior which is
important in controlling the pipeline corrosion in the seawater of Malaysia. The corrosion
rate result of the effect of sea water of Peninsular Malaysia on carbon steel pipe API SL
X42 and the corrosion behavior will determine the root cause of the failure.
Furthermore can broad its application range and therefore promises a large
economic impact. However, for subsea pipelines, literature reveals areas that might be
further developed from the conceptual and methodological viewpoint. This is because the
corrosion of underwater oil/gas pipes presents certain differences to that observed in other
types of marine facilities (seawater injection systems, offshore platforms and risers,
desalination pipes, etc.). Besides, the remedy of undersea pipeline segments is quite
problematic, since inspection methods and rehabilitation, are more expensive to those of
near sea surface equipment. Therefore, knowledge of corrosion attack explaining the
physiochemical mechanism, as well as the complexity and synergy of the undersea
corrosive factors (electrochemical) might be assessed, enabling further understanding on
issues of offshore pipelines corrosion and integrity management.
1.4
Significant of Study
The study of corrosion behavior will be useful to give information regarding
selecting the type of material for subsea piping/pipeline justification for changes in the
seawater composition over time led to more aggressive conditions which is resulting in
4
unacceptably high corrosion rate. In order to prevent unnecessary problems from the
corrosion attack at the pipeline, prediction type of material can be investigated and will
give sufficient protection to the pipeline system. The proper study of corrosion in
undersea pipeline in Malaysia's seawater will eventually have a major impact on the
safety, environmental preservation and the economics pipeline operation. The study will
also serve as a future reference that can be promulgated and exploited for through
existing corrosion researcher groups in the different district of peninsular Malaysia.
1.5
Research Objective
The objectives.,ofthis project are:1.
To determine the seawater contents m the different locations of Peninsular
Malaysia.
11.
To analyze the corrosion rate of sea water on the carbon steel in the different
seawater surrounding Peninsular Malaysia.
111.
1.6
To observe the corrosion behavior that occurs on the surface of the pipeline.
Scopes
This research will cover:1.
Identify the seawater contents from component that influence the life form and
heavy metal solution based on the Department of Environment Malaysia (DOE)
standard.
11.
Natural seawater was taken from seawater surrounding Peninsular Malaysia with
sea water that nearby the oil/gas plant processing.
111.
The sea water was divided into two groups; South China Sea and Straits of Malacca
Sea, since Malaysia is surrounded with the different seawater continent.
5
1v.
Material selected is the mm1mum allowable pipeline for oil/gas industries that
based on API standard - API SL X42.
v.
Heavy metal solution or ion parameters are based on the material composition.
vi.
The corrosion rate of the carbon steel is based on the Tafel Extrapolation
Technique and material is fully immersed during the experiment according to
ASTM Gl-90 and ASTM G102.
vii.
The study focuses on the external surface of the pipeline.
vni.
The corrosion behavior on the surface of the pipe is identified using Optical
Microscope and Stereomicroscope.
ix.
Immersed in the natural seawater to investigate corrosion behavior.
x.
Coating selection and mechanical testing will not be covered during the
experimentation.
6
CHAPTER2
LITERATURE REVIEW
Literature is important as a reference and comparison in this thesis. The strong
research report can provide a clear understanding of the relevant studies. This chapter
focuses on research and theoretical analyses have been done before and are relevant to a
study conducted
2.0
Introduction
This chapter introduces the variety of corrosion in the piping or pipeline system.
The condition will be focusing on the corrosion behavior, corrosion measurement and
oil/gas pipelines under the sea surrounding Malaysia only.
2.1
Types of Corrosion
According to American Society of Mechanical Engineers (ASME) corrosion may
occur in all piping and for the undersea piping need much necessity. Corrosion is the
ongoing damage of material by chemical reaction with its environment. Corrosion is a
separate reaction process on a metal surface where the loss of metal and production of
electrons in anodic areas and the consumption of these electrons in the cathodic areas.
The reaction process means that the electrochemical oxidation of metals in reaction
with an oxidant such as oxygen. Rusting, the formation of iron oxides is a familiar example
of electrochemical corrosion. This type of corrosion typically can create oxide(s) or salt(s)
of the original metal. Corrosion can be divided into two type internal and external
7
corrosion. According to DNV (2004), most common corrosion can be categorized as
follows:
•
General corrosion - Normally called a uniform corrosion because of the metal loss is
uniform from the surface of the metal.
•
Localized corrosion - This type of corrosion ensue when the metal surface is partly
covered with protective film, high or stagnant flow rate. Localized corrosion is
characterized by the formation of severely corroded regions separated by sharp steps
from neighboring areas.
•
Stress-corrosion cracking (SCC) - SCC results from the combination of corrosion
and tensile stress that can damage the material by cracking (Kadry, 2008). For SCC to
ensue, these conditions need to be considered:
1) An effective environment develops on the pipe surface
2) The pipe is susceptible to SCC
3) A tensile stress of sufficient magnitude is present
•
Hydrogen Embrittlement (HIC) - Hydrogen embrittlement consequences from the
simultaneous co-deposition of the primary metal and hydrogen on the surface of the
work piece (cathode). The hydrogen is available from the water in aqueous plating
bath chemistries. Hydrogen co-deposition can occur in the plating process either
during the actual electrolytic deposition or during the cleaning and acid pickles
preceding the plating bath.
•
Erosion Corrosion - Resulted from the combined action of chemical attack and
mechanical wear (Callister, 2003). For erosion corrosion to occur, it involves the
repetitive formation and the damage of the surface film.
8
2.1.1 External Corrosion in the Undersea
In external corrosion of undersea pipe, the overall rate of corrosion on the pipeline
external surface is detected by the ratio of anode area to cathode area, the concentration of
cathodic reactant and the resistivity of the local environment which determines the rate of
transport of ions between the anodic and cathodic areas.
The external corrosion process is the dissolution of the iron of the pipelines in the
anodic areas as charged positive ions into the sea water or seabed sediment. The higher the
availability of the oxygen to the metal surface, the higher the potential rate of corrosion.
Oxygen access to the bare metal surface increases as the temperature of the water decrease.
Pipelines are at the high risk of corrosion in cold water moving at high velocity (Nybord,
2005).
ﾷｾ＠ ..
CATHODE
p-...
:+20-- ... IH;a
Ｑｾﾷ＠
I
i
f
I
o,,- 2Hpj
,! ELECTAOL 'W'TE
(WATER.
_.,..,!
,/
Figure 2.1 Electrochemical Reaction Occurring during Corrosion of Iron Metal in
solution condition.
2.1.2 Formation of Corrosion with Seawater as an Electrolyte
In order to observe the formation of corrosion to ensue in the undersea, iron and
steel is placed in the seawater and corrosion begin to form as a reaction in which the
oxidation of metal is the anodic or corroding part of a corrosion cell. Chemical reactions at
the anode involve the release of electrons and conversion of metal from a solid to an ion
9
Faculty of Manufacturing Engineering
THE EFFECT OF SEAWATER ON THE CORROSION
BEHAVIOR OF NATURAL GAS PIPELINES IN
MALAYSIA
Suziee Binti Sukarti
Master of Manufacturing Engineering
2013
THE EFFECT OF SEAWATER ON THE CORROSION
BEHAVIOR OF NATURAL GAS PIPELINES IN
MALAYSIA
SUZIEE BINTI SUKARTI
A thesis submitted
In fulfillment of the requirement for the degree of Master of Manufacturing
Engineering (Manufacturing System Engineering) in Manufacturing Engineering
Faculty of Manufacturing Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
2013
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
(Manufacturing System Engineering). The member of supervisory committee is as follow:
Dr Mohd Asyadi 'Azam Bin Mohd Abid
DECLARATION
I declare that this thesis entitle "The Effect of Seawater On The Corrosion Behavior
Of Natural Gas Pipelines In Malaysia" 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.
Signature
Name
Date
SUZIEE BINTI SUKARTI
DEDICATION
To my beloved parents, Sukarti bin Sukimi and Siti Masrah binti Yusoff, all my friends.
Thank you for the continuous support and encouragement.
ABSTRAK
Air laut ialah kimia yang agresif secara semulajadi, cecair yang kompleks yang memberi
kesan kepada hampir semua struktur bahan pada tahap tertentu. Kakisan dalam air laut
adalah bergantung kepada beberapa faktor seperti komposisi bahan, sifat kimia air, pH,
biofouling, organisma mikrobiologi, pencemaran dan suhu. Pemahaman terhadap faktor
yang memuerikesankepada karatan di dalam air laut dapat membantu rekabentuk bahan,
komponen dan sistem untuk pengggunaan optimum dan hayat struktur bahan. Satu kajian
telah dijalankan untuk mengkaji kesan perbezaan air laut di sekitar Semenanjung
Malaysia ke atas keluli karbon yang berfungsi sebagai saluran paip bqgipetroleum dan
gas asli. -Kaedah Extrapolasi Tafel telah dtguna/a:ur-bagi menilai kadar karatan keluli
karbon dengan menggunakan air laut yang berbeza sebagai eletrolit. Dalam eksperimen
ini, keluli karbon AP! 5L X42 telah digunakan dan air laut yang diambil adalah dari Laut
China Se Iatan dan Laut Se/at Me/aka. Se lain pengiraan kadar kakisllfTjenis karatan juga
telah dibincangkan berdasarkan morfologi asas dan kandungan air laut jJ1ga ditentukan.
Didapati bahawa kadar kakisan spesimen keluli karbon adalah leblh noble di Se/at
}..Jelaka-Lautdaripada itu di L-aut China -Selatan. -variasi keputusan diperolehi iaitu
diantara 0. 10 -0. 25 mm I tahun. Karatan jenis seragam dan setempat didapati menyerang
permukaan spesimen dengan teruk. Kadar hakisan yang lebih rendah dicapai dengan
kandungan natrium klorida dan pH yang lebih tinggi. Sebahagian daripada bahan yang
larut seperti oksida ferum juga menyumbang pada pembentukan karat. Secara umumnya,
Laut China Selatan adalah lebih baik bagi penggunaan bahan ini walaupun bahan ini
boleh digunakan di kedua-dua jenis laut.
ABSTRACT
Seawater is inherently chemically aggressive, complex fluid that affects nearly all
structural materials to some extent. Corrosion in the seawater is dependent on a number of
factors such as material composition, water chemistry, pH, biofouling, microbiological
organisms, pollution and contamination and temperature. Understanding how these factors
may affect corrosion in seawater can support the design of materials, components, and
systems for optimal service performance and structural life. A study was taken to
investigate the effect of different seawater surrounding Peninsular Malaysia on the carbon
steel having app1ication as petroleum/natural gas pipeline. The Tafel Extrapolation
technique has been applied to evaluate the corrosion rate of the carbon steel and different
locations of natural seawater have been used as the electrolyte solution. In this experiment,
Carbon steel API SL X42 were utilized and the seawater is taken from the South China Sea
and Strait of Malacca. Beside the corrosion rate calculating the type of corrosion attack has
also been discussed on the basis of the morphology and the content properties of seawater
are determined. It is found that the corrosion rate of the carbon steel --specimen is
Sea 1han 1:hat in the-south China Sea. The
significantly nobler· in-the-Strait ｯｦｾＱ｡ｬ｣＠
results varied from 0.01 to 0.025 mm/year. Immersion test of two hours and ten days were
carried out to determine the corrosion product that formed at the surface of pipe. Localized
corrosion (pitting) and uniform corrosion attacked the surface specimen severely for each
sea. The lower corrosion rate is achieved with higher contents of sodimn chloride and
salinity. Some of the dissolved material such as Iron oxide also distributes to the formation
-0f cfilmsion. -Gencrally;---from--the resuit, -soulh -ch.ina Sea is more favorable in the
application-ef-trns-materiai-even theugh the material is-aGCeptahle in both seas.
ii
ACKNOWLEDGEMENT
First and foremost i offer my sincerest gratitude to my PSM supervisor, Dr. Mohd Asyadi
'Azam Bin Mohd Abid for the advice and guidance. Besides, i would like to thank my
parents, family, friends, lecturers, laboratory technicians and UteM staffs. Finally, i am
really grateful to Universiti Teknikal Malaysia (UTeM), especially to faculty of
Manufacturing Engineering (FKP) for providing me with all the knowledge.
iii
TABLE OF CONTENT
PAGE
APPROVAL
DECLARATION
DEDICATION
ABSTRAK
ABSTRACT
ACKNOWLEDGEMENT
LIST OF TABLES
LIST OF FIGURES
LIST OF ABBREVIATIONS
LIST OF APPENDICES
ll
m
VI
vu
IX
x
OIAPTER
1: INTRODUCTION
1. 0
1.2
1.3
1.4
1.4
1.5
1.6
1
2
3
4
4
5
5
Introduction
Problem statement
Summaries of problem statement
Expected Results
Significant of studies
Objective
Scopes
2: LITERATURE REVIEW
2. 0 Introduction
2.1 Types of Corrosion
2.1. l External Corrosion in the Undersea
2.1.2 Formation of Corrosion With Seawater as Electrol)te
2.2 Undersea Corrosion Mechanism
2.3 Offshore-Oil and Gas Piping
2.3 .1 Grades of Pipelines
2.4 Seawater Surrounding Malaysia
2.5 Environmental Influence on Corrosion
2.5.1 The Effect of Temperature, Salinity, Oxygen and pH on Marine Corrosion
2.6 Electrochemistry Techniques for Corrosion
2.6.1 Electrochemical measurement
2.6.2 Corrosion Surface Analysis
2.6.2. l Stereomicroscope
2.6.2.2 Optical Microscope
2.6.2.3 Differences Between OM and Stereomicroscope
2. 7 Seawater Content Measurement
2.7.1 Spectrophotometer
2.7.1 Incubator
iv
7
7
9
9
11
12
13
14
15
16
16
17
18
18
19
19
20
20
20
2.7.3
21
Multiprobe
3: RESEARCH METHODOLOGY
3 .1 Seawater Location
3.2 Seawater Content Analysis
3.2.1 Spectrophotometer HACH DR2700
3.2.2 Multiprobe YSI Professional Plus
3.2.3 UV Lamp and Binder Incubator BD115
3 .3 Material Selection
3.4 Material Sample Preparation
3.5 Experimental Study
3.5.1 Extrapolation Corrosion Test
3.5.2 Corrosion Surface Analysis
3 .5. 3 Immersion Test
24
26
26
29
29
31
32
34
34
36
37
4: RESULTS AND DISCUSSIONS
4.1
4.2
4. 3
4. 4
4.5
4.6
Observation on Immersion Test
4 .1.1
Microstructure Morphology of Corrosion Product
Seawater Contents
4.2.1 Turbidity, pH and Salinity Result
4.2.2 Seawater Microorganism
4.2.3 Heavy Metal Solution in Seawater
Electrochemical Analysis
Corrosion Rate Analysis
Seawater Content after the Electrochemical Testing
4.5.1 Iron, Manganese and Aluminum Effect
Surface Corrosion Product after Electrochemical Testing
38
40
42
43
44
45
46
50
51
52
56
5: CONCLUSIONS AND RECOMMENDATIONS
5 .1
5 .2
58
Conclusions
Recommendations
59
60
REFERENCES
APPENDICES
64
v
LIST OF TABLES
TABLE
TITLE
PAGE
2.1
Line pipe physical properties
13
3.1
Pipe Sample Properties
20
3.2
Sample Preparation
20
3.3
Seawater locations in Peninsular Malaysia
22
3.4
Specification of Gambry Reference 600
24
3.5
Parameters and reagents
25
4.1
Parameter Value for Seawater Using Multiprobe
43
4.2
E. coli as Microorganism in the Seawater
44
4.3
Metal Solution Value
45
4.4
Seawater Contents for Peninsular Malaysia
46
4.5
Tafel Curves
47
4.6
Corrosion Potential and Corrosion Rate Values
48
4.7
Total anodic current, corrosion current density, corrosion potential and corrosion
4.8
penetration rate.
51
Contents of Seawater after the Corrosion Test
52
vi
LIST OF FIGURES
FIGURE
2. 1
TITLE
PAGE
Electrochemical Reaction Occurring During Corrosion of
Iron Metal in solution condition
2.2
8
Differential corrosion cell by differences in soils. Arrow indicates
direction of ionic and electronic current flow
10
2.3
Average Sea Temperature
14
3.1
Methodology Flowchart
18
3.2
API 5 L X42 Pipes
19
3.3
Water Quality Monitoring Station.
22
3.4
Experimental Setup for Reference 600
23
3.5
Experiment to determine the Manganese
26
3.6
Experiment Equipment (A) Spectrophotometer (B) Binder Incubator
26
4.1
Schematic Illustration oflmmersion Test
39
4.2
(a) Example Observations on Two Hours Immersion,
(b) Example Observation on 10 Days Immersion
39
4.3
Illustration oflmmersion Test after 10 Days
40
4.4
Straits of Malacca Corrosion Products after 10 Days oflmmersion
40
(a) N. Sembilan (b) Johor (c) Melaka.
4.5
Straits of Malacca Corrosion Products after 10 Days oflmmersion
(a) Terengganu (b) Kelantan (c) Pahang.
4.6
41
Magnified Observation on Corrosion Product Using OM
(a) 20µm (b) 50µm for API 5L X42 and (c) Microstructure Comparison
41
4.7
Magnified Observation on API 5L X42 pipe when it's dried
42
4.8
Straits of Malacca Tafel Extrapolation Graph
46
4.9
South China Sea Tafel Extrapolation Graph
47
vii
4.10
Seawater Surrounding Peninsular Malysia Tafel Extrapolation Graph
4.11
(a), (b) and (c) Differences of Seawater Content before and after Tafel
49
Experiment
53
4.12
Iron Hydroxide formed at the surface of the pipe
55
4.13
Seawater after Electrochemical Test
56
4.14
Uniform Surfaces and Pitting Corrosion Attack on the Surface of Carbon Steel
56
4.15
Optical Microscope Magnifications on Pitting and Uniform Corrosion
57
viii
LIST OF ABBREVIATIONS
API
American Petroleum Institute
ASTM
American Society for Testing and Materials
ASME
American Society of Mechanical Engineers
A
Ampere
K
Kelvin
Kg
Kilogram
mis
Meter per second
MIC
Microbiologically Influenced Corrosion
Mpa
Mega pascal
Mm
Milileters
pH
Potential of Hydrogen
sec
Stress Corrosion Cracking
TDS
Total Dissolved Solid
µm
Micronmeter
Fe
Ferum
w
Hidrogen Ion
Mn
Manganese
Al
Aluminium
P.P.T
Part per Thousand
N.T.U
Nephelometric Turbidity Units
ix
LIST OF APPENDICES
PAGE
TITLE
APPENDIX
Peninsular Malaysia: Marine Monitoring Location
43
B
Metal Galvanic Series in Seawater
44
c
Galvanic Corrosion Chart
45
D
Carbon Steel Content
46
E
ASTMG102
47
F
ASTMGl
54
A
x
CHAPTERl
INTRODUCTION
This section basically is an introduction to pipelines underneath seawater in
Malaysia and problem statement for this research. The graphic illustrations can be found in
the appendices.
1.0
Introduction
In recent years, since the first oil pipelines are embedded underneath sea using
welded steel, the most common basic purpose of pipelines underneath sea still remains the
same as the network for the fuel (oil/gas) transportation. The first cross-country pipeline
is called PLUTO (Pipe Line under the Ocean) which is built during the World War II,
since then the technology has improved, the undersea pipeline is a practical ways to
transport water, fuel, oil and gases, therefore carbon steel or are commonly used.
Malaysia also has many companies that develop undersea oil and gas pipelines
that have the capability to design, build, operate and maintain gas processing and
transmission pipeline infrastructure around peninsular and east Malaysia. Natural energy
problem, including environmental aspects had changed the character of pipelines
underneath sea water. According to Institute of Engineering Malaysia (2003), Malaysia
warm seawater is threatened by direct and indirect pollution sources. These changes that
occurred undersea will lead to the pipeline corrosion and simultaneously have a tendency
to degrade. Sea water corrosion involves reactions where the metal surface is transformed
into metal oxides or hydroxides (like rust) (NDV, 2004). Apart from the natural energy
1
problem and environmental changes, the rate of seawater corrosion depends on several
factors like metal impurities, temperature, oxygen access, metallic contact (conductive)
with dissimilar metals, sea water flow velocities, type of metals, surface protection and
stresses.
Failure of submarine pipeline by corrosion has been a familiar phenomenon in
processing plants resulting in unscheduled plants shut down, in consequences; there are
heavy losses in industrial production and disruptions to civil amenities. A lot of research
has been made to overcome the problem with underwater pipeline and its repair still
remained a challenge.
1.1
Problem Statement
Corrosion is an electrochemical process which is the dissolution of the pipeline in
the anodic areas as charged positive ions into the seawater or sea bed sediment. These
ferrous ions react to form oxides and hydroxide and may form ferric salts if the water is
well oxygenated. Palmer (2008) suggests that pipelines buried undersea ought to be an at
least risk of corrosion because of the oxygen content should be low but the offshore
pipelines become often acceptors of corrosion attack, which is enhanced by undersea
biochemical factors. The concentration of salts in the environment and the local
temperature affects the resistivity and pH value, hence, both the potential corrosiveness of
the environment and the coating degradation behavior.
In addition if the seawater has the presence of high chloride or low sulfate levels
then the pipelines are at higher than normal risk of corrosion as the corrosion products of
iron will be more soluble. The activity of the sulfate reducing bacteria also alters with
salinity and temperature. Salinity changes occur in shallow inshore waters in hot and warm
climates (e.g. The south east of Arabian Gulf and Malaysia). A small change in this one of
2
the parameters will change the corrosion rate considerably and when the corrosion
products are not deposited on the steel surface, a very high corrosion rate of several
millimeters per year can occur. (Nyborg, 2005).
The undersea corrosion issue is of great interest for organizations managing
offshore networks for oil/gas transportation. Oil and gas supply companies, engineering
consultants and inspection agents, pay a lot of money to cope with marine corrosion,
developing inspection methods and prevention technologies to enhance the integrity of
undersea pipelines. For example, PETRONAS has undertaken collaborative development
with the Commonwealth Scientific & Industrial Research Organization (CSIRO) to
develop a novel composite prepreg for use in underwater repair of pipelines, with the
solution to be known as PIPEASSURE (Petronas, 2011). Knowledge acquisition from
corrosion literature and expertise for marine facilities integrity management has been the
focus of the research. Thus, knowledge based expert systems are designed and
implemented by modifying computational methods and tools, which are mainly applied in
investigating the industrial system failure. The effects of the corrosive action are metal
loss, reduction of mechanical strength and thereof premature aging of the pipe segments.
1.2
Summary of Problem Statement
The problem can be summarized in three critical points:1.
Influence of seawater on the corrosion piping is apparent nonetheless limited
information exists on the variation of seawater effect on external pipeline
corrosion surrounding Peninsular Malaysia
11.
The variation of seawater characteristic that keep changing due to several factors
such as contaminations might present a different potential corrosion risk and
variable rate of corrosion that can give major on safety, environmental
3
preservation and the economics pipeline operation.
11 1.
The undersea pipeline corrosion is enduring studies that keep varying due to
several factors of seawater variation environment.
1.3
Expected Findings
This particular study can give a better understanding of corrosion behavior which is
important in controlling the pipeline corrosion in the seawater of Malaysia. The corrosion
rate result of the effect of sea water of Peninsular Malaysia on carbon steel pipe API SL
X42 and the corrosion behavior will determine the root cause of the failure.
Furthermore can broad its application range and therefore promises a large
economic impact. However, for subsea pipelines, literature reveals areas that might be
further developed from the conceptual and methodological viewpoint. This is because the
corrosion of underwater oil/gas pipes presents certain differences to that observed in other
types of marine facilities (seawater injection systems, offshore platforms and risers,
desalination pipes, etc.). Besides, the remedy of undersea pipeline segments is quite
problematic, since inspection methods and rehabilitation, are more expensive to those of
near sea surface equipment. Therefore, knowledge of corrosion attack explaining the
physiochemical mechanism, as well as the complexity and synergy of the undersea
corrosive factors (electrochemical) might be assessed, enabling further understanding on
issues of offshore pipelines corrosion and integrity management.
1.4
Significant of Study
The study of corrosion behavior will be useful to give information regarding
selecting the type of material for subsea piping/pipeline justification for changes in the
seawater composition over time led to more aggressive conditions which is resulting in
4
unacceptably high corrosion rate. In order to prevent unnecessary problems from the
corrosion attack at the pipeline, prediction type of material can be investigated and will
give sufficient protection to the pipeline system. The proper study of corrosion in
undersea pipeline in Malaysia's seawater will eventually have a major impact on the
safety, environmental preservation and the economics pipeline operation. The study will
also serve as a future reference that can be promulgated and exploited for through
existing corrosion researcher groups in the different district of peninsular Malaysia.
1.5
Research Objective
The objectives.,ofthis project are:1.
To determine the seawater contents m the different locations of Peninsular
Malaysia.
11.
To analyze the corrosion rate of sea water on the carbon steel in the different
seawater surrounding Peninsular Malaysia.
111.
1.6
To observe the corrosion behavior that occurs on the surface of the pipeline.
Scopes
This research will cover:1.
Identify the seawater contents from component that influence the life form and
heavy metal solution based on the Department of Environment Malaysia (DOE)
standard.
11.
Natural seawater was taken from seawater surrounding Peninsular Malaysia with
sea water that nearby the oil/gas plant processing.
111.
The sea water was divided into two groups; South China Sea and Straits of Malacca
Sea, since Malaysia is surrounded with the different seawater continent.
5
1v.
Material selected is the mm1mum allowable pipeline for oil/gas industries that
based on API standard - API SL X42.
v.
Heavy metal solution or ion parameters are based on the material composition.
vi.
The corrosion rate of the carbon steel is based on the Tafel Extrapolation
Technique and material is fully immersed during the experiment according to
ASTM Gl-90 and ASTM G102.
vii.
The study focuses on the external surface of the pipeline.
vni.
The corrosion behavior on the surface of the pipe is identified using Optical
Microscope and Stereomicroscope.
ix.
Immersed in the natural seawater to investigate corrosion behavior.
x.
Coating selection and mechanical testing will not be covered during the
experimentation.
6
CHAPTER2
LITERATURE REVIEW
Literature is important as a reference and comparison in this thesis. The strong
research report can provide a clear understanding of the relevant studies. This chapter
focuses on research and theoretical analyses have been done before and are relevant to a
study conducted
2.0
Introduction
This chapter introduces the variety of corrosion in the piping or pipeline system.
The condition will be focusing on the corrosion behavior, corrosion measurement and
oil/gas pipelines under the sea surrounding Malaysia only.
2.1
Types of Corrosion
According to American Society of Mechanical Engineers (ASME) corrosion may
occur in all piping and for the undersea piping need much necessity. Corrosion is the
ongoing damage of material by chemical reaction with its environment. Corrosion is a
separate reaction process on a metal surface where the loss of metal and production of
electrons in anodic areas and the consumption of these electrons in the cathodic areas.
The reaction process means that the electrochemical oxidation of metals in reaction
with an oxidant such as oxygen. Rusting, the formation of iron oxides is a familiar example
of electrochemical corrosion. This type of corrosion typically can create oxide(s) or salt(s)
of the original metal. Corrosion can be divided into two type internal and external
7
corrosion. According to DNV (2004), most common corrosion can be categorized as
follows:
•
General corrosion - Normally called a uniform corrosion because of the metal loss is
uniform from the surface of the metal.
•
Localized corrosion - This type of corrosion ensue when the metal surface is partly
covered with protective film, high or stagnant flow rate. Localized corrosion is
characterized by the formation of severely corroded regions separated by sharp steps
from neighboring areas.
•
Stress-corrosion cracking (SCC) - SCC results from the combination of corrosion
and tensile stress that can damage the material by cracking (Kadry, 2008). For SCC to
ensue, these conditions need to be considered:
1) An effective environment develops on the pipe surface
2) The pipe is susceptible to SCC
3) A tensile stress of sufficient magnitude is present
•
Hydrogen Embrittlement (HIC) - Hydrogen embrittlement consequences from the
simultaneous co-deposition of the primary metal and hydrogen on the surface of the
work piece (cathode). The hydrogen is available from the water in aqueous plating
bath chemistries. Hydrogen co-deposition can occur in the plating process either
during the actual electrolytic deposition or during the cleaning and acid pickles
preceding the plating bath.
•
Erosion Corrosion - Resulted from the combined action of chemical attack and
mechanical wear (Callister, 2003). For erosion corrosion to occur, it involves the
repetitive formation and the damage of the surface film.
8
2.1.1 External Corrosion in the Undersea
In external corrosion of undersea pipe, the overall rate of corrosion on the pipeline
external surface is detected by the ratio of anode area to cathode area, the concentration of
cathodic reactant and the resistivity of the local environment which determines the rate of
transport of ions between the anodic and cathodic areas.
The external corrosion process is the dissolution of the iron of the pipelines in the
anodic areas as charged positive ions into the sea water or seabed sediment. The higher the
availability of the oxygen to the metal surface, the higher the potential rate of corrosion.
Oxygen access to the bare metal surface increases as the temperature of the water decrease.
Pipelines are at the high risk of corrosion in cold water moving at high velocity (Nybord,
2005).
ﾷｾ＠ ..
CATHODE
p-...
:+20-- ... IH;a
Ｑｾﾷ＠
I
i
f
I
o,,- 2Hpj
,! ELECTAOL 'W'TE
(WATER.
_.,..,!
,/
Figure 2.1 Electrochemical Reaction Occurring during Corrosion of Iron Metal in
solution condition.
2.1.2 Formation of Corrosion with Seawater as an Electrolyte
In order to observe the formation of corrosion to ensue in the undersea, iron and
steel is placed in the seawater and corrosion begin to form as a reaction in which the
oxidation of metal is the anodic or corroding part of a corrosion cell. Chemical reactions at
the anode involve the release of electrons and conversion of metal from a solid to an ion
9