vii
TABLE OF CONTENTS
CHAPTER
DECLARATION
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
ABSTRAK
TITLE
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF ABBREVIATION AND SYMBOLS
LIST OF APPENDICES
CHAPTER 1 INTRODUCTION
1.0 Overview
1.1 Background of the Problem
1.2 Research Problem
1.3 Research Objectives
1.4 Research Scope
1.5 Importance of Study
CHAPTER 2 LITERATURE REVIEW
2.0 Introduction
2.1 Underground Network of Transmission Pipeline
2.2 Corrosion Influence upon Pipeline Integrity
PAGE
6
4
5
3
4
1
2
6
6
8 vi vii xii xiv ii iii iv v xviii xxi
1

2.3 Corrosion Theory
2.4 Corrosion of Underground Structures
2.5 Corrosion in Soil
2.6 Corrosion Parameters Related to Soil
Environment
2.6.1 Types of Soil
2.6.2 Soil Resistivity
2.6.3 Soil Texture and Particle Size
2.6.4 Moisture Content
2.6.5 Plasticity Index
2.6.2 Clay Content
2.7 Corrosion Testing
2.7.1 Service and Field Corrosion Test
2.7.2 Laboratory Corrosion Test
2.8 Fundamentals of Linear and Power Law
Corrosion Model
2.9 Previous Works on External Corrosion Model
2.9.1 Ramanoff’s Model
2.9.2 Early Classification of Constant ‘ k’ and
Constant ‘ v’
2.9.3 Current Work on the Classification of
Constant ‘ k’
and Constant ‘ v’
2.9.3.1 Li’s Model
2.9.3.2 Velazquez’s Model
2.10 Concluding Remarks
CHAPTER 3 METHODOLOGY
3.0 Introduction
3.1 Overview of Corrosion Study Methodology
3.2 Selection and Preparation of Steel Coupon
3.3 Actual Field Work
3.4 Simulated Field Work viii
9
11
24
26
26
19
20
21
23
27
15
16
16
18
11
14
14
31
33
28
28
29
33
33
36
38
42

3.5 Laboratory Test
3.5.1 Overview
3.5.2 Preparation of Soil Sample
3.5.2.1 Soil Sample for Clay Content
3.5.2.2 Soil Sample for Plasticity Index
3.5.2.3 Soil Sample for Moisture Content
3.5.2.4 Soil Sample for Particle Size
3.5.2.5 Soil Sample for Control Sample
3.6 Assessment of Corrosion and Soil Related
Parameters
3.6.1 Corrosion Assessment
3.6.2 Soil Testing
3.6.2.1 Moisture Content (MC) Test
3.6.2.2 Plasticity Index (PI) Test
3.6.2.3 Particle Size (PS) Test
3.6.2.4 Clay Content (CC) Test
3.7 Data Analysis
3.8 Concluding Remark
CHAPTER 4 ANALYSIS OF FIELD WORK AND SIMULATED
FIELD WORK
4.0 Introduction
4.1 Field Work - Site Description
4.1.1 Corrosion Data and Soil Properties
4.1.2 Normality Test
4.1.3 Removal of Outliers
4.1.4 Simple Linear Regression (SLR) Analysis
4.1.5 Correlation Analysis
4.1.6 Classification Test – Principal Component
Analysis (PCA)
4.1.7 Multiple Regression Analysis
4.2 Simulated Field Work
72
74
76
77
66
66
67
71
80
81 ix
46
46
62
63
64
65
58
61
61
61
55
57
58
49
49
52
53
66

4.2.1 Corrosion Data and Soil Properties Simulated
Field Work
4.2.2 Normality Test for Simulated Field Work
4.2.3 Detection of Outliers for Simulated Field Work
4.2.4 Simple Linear Regression (SLR) Analysis for
Simulated Field Work
4.2.5 Correlation Analysis for Simulated Field Work
4.2.6 Principal Component Analysis (PCA) for
Simulated Field Work
4.2.7 Multiple Regression Analysis for Simulated
Field Work
4.3 Concluding Remarks
DATA ANALYSIS OF LABORATORY WORK CHAPTER 5
5.0 Introduction
5.1 Laboratory Test Procedure
5.1.1 Corrosion Data
5.1.2 Corrosion Growth Pattern
5.2 Relationship between Soil Properties and Corrosion
Rate
5.3 T-test Analysis on Metal Loss Factor
5.4 T-test Analysis on Time-Factor
5.5 Concluding Remarks
CHAPTER 6 DISCUSSION
6.0 Introduction
6.1 Corrosion Behaviour based on Actual Field Work
6.1.1 Single Regression
6.1.2 Multiple Regression
6.1.3 Principal Component Analysis
6.1.4 Comparison between Actual and Simulated
Field Works
110
110
110
112
113
114
94
95
95
96
101
104
107
109
110 x
82
90
91
92
86
87
88
93
94

6.2 Corrosion Behaviour based on Parametric Study
6.2.1 Paired t-test
6.2.2 Optimum Value of Soil Properties
CHAPTER 7 CONCLUSION AND RECOMMENDATION
7.0 Conclusion
7.1 Recommendation
REFERENCES
APPENDIX A Corrosion Data and Soil Properties Table
APPENDIX B Statistical Data Analysis Result
118
119
121
128
143 xi
115
115
117
118

xii
4.3
4.4
4.5
4.6
3.1
3.2
4.1
4.2
4.7
4.8
4.9
4.10
4.11
4.12
4.13
5.1
5.2
TABLE NO.
2.1
2.2
2.3
5.3
5.4
LIST OF TABLES
TITLE
Classification of soil corrosivity based on resistivity
(Palmer, 1989)
Typical grain size of clay particle (Source: Das, 2010)
Summary of proposed soil parameter related to constant k and v
Percentage of particle size for laboratory test
Example calculation of particle size
Site condition
Summary of all parameters for actual field work
Extreme values of box plot for actual field work
New data set after outliers removed
Pearson correlation test for actual field work
Spearman’s rho correlation test for actual field work
Summary of classification test for actual field work
Brief information for the selected type of soil
Summary of all parameters for simulated field work
New data set after outliers removed for simulated field work
Pearson correlation test for simulated field work
Spearman’s rho correlation test for simulated field work
Summary of classification test for simulated field work
Summary of soil parameters for laboratory test
R
2
of linear and power model for corrosion growth pattern of laboratory test.
Paired t-test for different moisture content
Paired t-test for different clay content
PAGE
16
20
30
105
105
73
74
77
77
56
63
67
69
79
81
83
87
90
90
92
95
99

5.5
5.6
6.1
6.2
6.3
5.7
5.8
5.9
5.10
Paired t-test for different plasticity index
Paired t-test for different particle size
Paired t-test for moisture content on time function
Paired t-test for clay content on time function
Paired t-test for plasticity index on time function
Paired t-test for particle size on time function
Summary of multiple regression analysis
Summary of the result of actual and simulated field work
Summary of classification for constant k and v xiii
106
106
107
108
108
108
113
115
116

xiv
2.10
3.1
3.2
3.3
3.4
3.5
FIGURE NO.
2.1
2.2
2.3
LIST OF FIGURES
TITLE
Peninsular Gas Utilisation (PGU) network
The basic corrosion process.
Exposure of underground pipeline to the soil environment
2.4
2.5
2.6
(source: Willmott and Jack in Uhlig’s Corrosion
Handbook, 2011)
Effect of moisture content on the corrosivity range of the soil (Source: Ismail and El-Shamy, 2009)
Effect of moisture on soil resistivity (Source: Romanoff,
1957)
General corrosion model showing changing phase of corrosion process and parameterisation (Source: Melchers,
2.7
2.8
2.9
2006)
Power law behaviour was observed for short term (less than 12 months) corrosion process (Source: Melchers,
2006)
Apparatus for conducting laboratory corrosion tests in soil
(Source: ASTM G162-99)
Example of linear corrosion model
PAGE
7
10
13
18
18
22
22
24
25
Example of power law corrosion model
Overview of research methodology
Pipe sample cutting using hot-cut method
Cold-cut method applied to remove heat affected zone
Steel coupons with (left) and without coating (right)
Coupons cleaning using acetone prior to corrosion test
25
34
36
36
37
38

3.6
3.7
3.8
3.9
3.10
3.11
3.12
3.13
3.14
3.15
3.16
3.17
3.18
3.19
3.20
3.21
3.22
3.23
3.24
3.25
3.26
3.27
3.28
3.29
3.30
3.31
3.32
4.1
Flow chart for field work
Hole digging/boring process using mechanical auger
Coupon sealed in plastic envelop ready for installation in the borehole
Layout of coupon position in borehole
Flow chart for Simulated Field Work
Coupon installed in soil medium for Simulated Field Work
Preparation of simulated soil medium
Installation of soil medium in UTM area
Location where Simulated Field Work was conducted
Layout of coupons for laboratory test
Flow chart of laboratory test (OFAT approach).
Kaolin mixed with washed sand to design soil sample with clay content of 25%, 50%, 75% and 100%
Steel coupon used in the laboratory test
Steel coupon installed in saturated washed sand
De-ionized water used as electrolyte for laboratory test
Bentonite clay used to alter soil plasticity
Washed sand sample with plasticity index of 15, 30, 45 and 60
Oven-dried washed sand
Soil samples with different moisture contents (0%, 5%,
15%, 25% and 35%)
Sieving apparatus used in dry-sieving method
Different sizes of soils particles
Washed sand with different particle size distribution
Control samples for laboratory test
Mechanical cleaning process
Sample cleaned by immersing the coupon in cleaning solution
Cleaned sample was weighed and recorded
Overall flow of analysis procedure
Metal loss over time for SITE 1
50
51
51
52
53
54
54
60
65
70
45
45
47
48
50
41
43
44
44
55
56
57
58
59
60 xv
39
40
41

4.20
4.21
4.22
4.23
4.24
5.1
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
Metal loss over time for SITE 2
Metal loss over time for SITE 3
Metal loss over time for SITE 4
Metal loss over time for SITE 5
Effect of moisture content on metal loss
Effect of clay content on metal loss
Effect of plasticity index on metal loss
Effect of particle size on metal loss
Relationship between parameters obtained by PCA for metal loss
Relationship between parameters obtained by PCA for time factor
Metal loss over time for soil TYPE A
Metal loss over time for soil TYPE B
Metal loss over time for soil TYPE C
Metal loss over time for soil TYPE D
Metal loss over time for soil TYPE E
Metal loss over time for soil TYPE F
Metal loss over time for soil TYPE G
Effect of moisture content on metal loss for simulated field work
Effect of clay content on metal loss for simulated field work
Effect of plasticity index on metal loss for simulated field work
Effect of particle size on metal loss for simulated field work
Relationship between parameters obtained by PCA on metal loss for simulated field work
Relationship between parameters obtained by PCA on time factor for simulated field work
Metal loss over time under the influence of moisture content
89
91
89
89
92
97
79
85
85
86
88
84
84
84
85 xvi
70
70
76
76
78
71
71
75
75

5.2
5.3
5.8
5.9
5.10
5.11
5.12
5.4
5.5
5.6
5.7
Metal loss over time under the influence of clay content
Metal loss over time under the influence of plasticity index
Metal loss over time under the influence of particle size
Corrosion rate over time under the influence of moisture content
Corrosion rate over time under the influence of clay content
Corrosion rate over time under the influence of plasticity index
Corrosion rate over time under the influence of particle size
Relationship between moisture content and corrosion rate
Figure 5.10: Relationship between clay content and corrosion rate
Relationship between plasticity index and corrosion rate
Relationship between particle size and corrosion rate xvii
97
98
98
100
100
101
101
102
103
103
104

c
CC cc
CC
F
CC
SF
Cl
-
CR
CR
F
CR
SF ct
D e-
E h
* d max
W loss
°C
µm
A a
AFAT b bc bd
C
LIST OF ABBREVIATION AND SYMBOLS asterisk mark (significant value) maximum pit depth corrosion rate calculated from weight-loss measurement degree Celsius micrometre area in cm
2 regression coefficient all-factors-at-a-time power coefficient bicarbonate content bulk density carbon interception of linear model clay content chloride content
Clay Content (actual field work)
Clay Content (simulated field work) chloride content corrosion growth rate
Corrosion Rate (actual field work)
Corrosion Rate (simulated field work) coating type density in g/cm
3
(X70 = 8.29 g/cm
3
; X42 = 7.85 g/cm
3
) electrons reduction-oxidation potential xviii

Fe
Fe2+
Fe
2
O
3
H
2
O
K k
P
0.cal
P c
PCA
PGU
PI
PI
F
PI
SF
PL k
0,
k
1,
k
2…
K-S
LL m
MC
MC
F
MC
SF
MIC
ML
F
ML
SF
MRA n
0,
n
1,
n
2…
NGDS
O
2
OFAT
OH-
P/S pp iron ferrous ions iron ore/rust water a constant (8.76 x 10
4
mm/y) metal loss constant regression coefficient for metal loss
Kolmogorov-Smirnov normality test liquid limit slope/regression coefficient of linear model moisture content
Moisture Content (actual field work)
Moisture Content (simulated field work)
Microbiologically-Influenced Corrosion
Metal Loss (actual field work)
Metal Loss (simulated field work) multiple regression analysis regression coefficient for corrosion growth pattern
Natural Gas Distribution System oxygen one-factors-at-a-time hydroxyl ions pipe-to-soil potential predictive pit depth evaluation value of the environment principal component analysis
Peninsular Gas Utilisation plasticity index
Plasticity Index (actual field work)
Plasticity Index (simulated field work) plastic limit pipe-to-soil potential xix

T t t c
T
F
T
SF
UTM v
W
W
0 wc
RSM sc
Sig.
SLR
SPSS
SRB
S-W
PS
PS
F
PS
SF p-value
R
2 re rp x y y
ρ particle size
Particle Size (actual field work)
Particle Size (simulated field work) significant value coefficient of determination resistivity redox potential response surface method sulfate content significant value simple linear regression analysis
Statistical Package for Social Science
Sulphate-Reducing Bacteria
Shapiro-Wilk normality test time of exposure (hr) elapsed/exposure time thickness of the corroded layer
Exposure Time (actual field work)
Exposure Time (simulated field work)
Universiti Teknologi Malaysia corrosion growth pattern constant weight loss (g) initial weight water content independent variable year independent variable resistivity xx

xxi
LIST OF APPENDICES
APPENDIX
A
B
TITLE
Corrosion Data and Soil Properties Table
Statistical Data Analysis Result
PAGE
128
143