• Welding done along the joints of under water hydrocarbon pipelines.
• Preferential weld corrosion (PWC) occurs in the welded region.
• CO2 triggers PWC.
• Protective layer, FeCO3 precipitation disrupted due to weak acids HAc and pH
• United States , the cost of corrosion in 1986 amounted to US$160 billion.
*R. Barker, X. Hu, A. Neville and S. Cushnaghan, 'Assessment of Preferential Weld Corrosion of Carbon Steel Pipework in CO 2 -Saturated Flow-Induced Corrosion Environments', Corrosion, vol. 69, no. 11, pp. 1132-1143, 2013..
Figure 2 shows the corrosion in the internal part of the hydrocarbon pipeline
Figure 1: An example of typical weld corrosion in the pipeline occurred due to CO2 reaction.
PROJECT BACKGROUND
Does presence of Acetic Acid (HAc) affect preferentially on the formation of FeCO3 on to the surfaces of weld segments? What is the effect of pH value on weld segment corrosion rate with the presence of Acetic Acid (HAc)?
Problem StatementBackground
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
• R. Barker, X. Hu, A. Neville and S. Cushnaghan, 'Assessment of Preferential Weld Corrosion of Carbon Steel Pipework in CO 2 -Saturated Flow-Induced Corrosion Environments', Corrosion, vol. 69, no. 11, pp. 1132-1143, 2013
• K. Alawadhi and M. Robinson, 'Preferential weld corrosion of X65 pipeline steel in flowing brines containing carbon dioxide', Corrosion Engineering, Science and Technology, vol. 46, no. 4, pp. 318-329, 2011..
.
PROJECT BACKGROUND
• To investigate the presence of Acetic Acid (HAc) and its effect on the corrosion rate of the weld segments.
• To analyze the influence of pH on the FeCO3 formation on the weld segments.
• To perform surface analysis of weld segment under the presence of HAc and pH influence.
Objectives
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Scope of Study• Enables to cover one small critical area in the oil and gas industries.
• Help the industry to improve corrosion mitigation method.
• A research to improve the performance and reduce the cost of the industry
• Enhances knowledge and prepare for the real life working culture
LITERATURE REVIEW
HAZ- Base metal exposed to
heat.- Undergoes microstructure
change
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Figure 3 shows the segments in a weld region
*R. Barker, X. Hu, A. Neville and S. Cushnaghan, 'Assessment of Preferential Weld Corrosion of Carbon Steel Pipework in CO 2 -Saturated Flow-Induced Corrosion Environments', Corrosion, vol. 69, no. 11, pp. 1132-1143, 2013..
Figure 3: The microstructural observation of weld segments using Optical Microscope (OM) with magnification 50x (a) parent metal (b) HAZ and (c) weld metal.
Parent metal- Far from welding- Base metal
Weld metal- Fusion of filler metal and
PM metal- Different microstructure.
Preferential Weld Corrosion
LITERATURE REVIEW
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
CO2 Corrosion
Figure 4 :Schematic of FeCO3 formation on the steel surface in CO2 environmentRetrieved from: https:co2corrosionchem409.wikispaces.com/Corrosion+Mechanism?responseToken=a0ebe1b916b14bc311c48f0f73fde1c9//
*C. de Waard, D.E. Milliams, Corrosion 31, 5 (1975): p. 175.* S. Nes˘ic´, G.T. Solvi, J. Enerhaug, Corrosion 51, 10 (1995): p. 773.
LITERATURE REVIEW
Acetic Acid in CO2 corrosion
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
References Findings
J.-L. Crolet, N. Thevenot, A. Dugstad, (1999)
• A type of weak acid
• Short carboxylic chains
• The hydrogen center in the carboxyl group (−COOH) easily separates by ionization:
CH3CO2H → CH3CO2− + H+
S. Nes˘ic´, G.T. Solvi, J. Enerhaug, (1995)
• Partially soluble. Reservoir for H+ supply.
• Undissociated free HAc causes reduction of Hydrogen ion.
(cathodic reaction)
• Decreases the pH of the condensate Solubility of iron.
(anodic reaction)
LITERATURE REVIEW
Acetic Acid in FeCO3 formation
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation High
Temperature
High HAc concentration
undergoing partial ionization
Fe ¿ FeCO3 layer fail to form
High rate of
corrosion
Reference Findings
R. Nyborg and A. Dugstad(2007)
• Increases the solubility of iron due to un-dissociated HAc (Iron Acetate formation)
• is highly soluble, does not precipitate.
• FeCO3 formation is disrupted.
LITERATURE REVIEW
pH influence in the HAc reaction
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
References Findings
Hedges and McVeigh (1999) At low pH (4-5)
• thin FeCO3 formation
• HAc mostly forms
• Corrosion rate increases
A high pH (5-6)
• Less FeCO3 solubility
• Corrosion rate decreases
(fully mitigated if HAc is below 400ppm)
LITERATURE REVIEW
pH influence in the HAc reaction
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
References Findings
K.S. George* and S. Nes˘ic (2007)
At low pH (4-5) • High concentration of HAc• influences high anodic reaction
A high pH (5-6)• Less HAc concentration• less anodic reaction, yet slow cathodic
Figure 5: The effect of pH on potentiodynamic sweeps done on X65 steel corroding in aqueous solutions purged with CO2 containing 100 ppm total acetic species at 1,000 rpm, 22°C.
Retrieved; *K. George and S. Nesic, 'Investigation of Carbon Dioxide Corrosion of Mild Steel in the presence of Acetic Acid', NACE International, vol., 2007
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Total Corrosion Rate
Type of corrosion MeasurementsConnection Diagram
Intrinsic Corrosion • Self-corrosion undergone by a metal.
Galvanic Corrosion • Corrosion due to potential difference between metal segments.
Total Corrosion [CRTotal = CRIntrinsic + CRGalvanic]
LITERATURE REVIEW
*A.E. Jenkins, W.Y. Mok, C.G. Gamble, Baker Petrolite; G.E. Dicken, CAPCIS, “Development of Green Corrosion Inhibitors for Preventing Under Deposit and Weld Corrosion, Paper no. 87558-MS,” Presented at 2004 SPE International Symposium on Oilfield Corrosion, Aberdeen, United Kingdom.
*K. Alawadhi, M. Robinson, A. Chalmers, and I.G. Winning, “Inhibition of weld corrosion in flowing brines containing carbon dioxide, Paper no. 622,” Presented at 2008 NACE Conference.
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
METHODOLOGY
PROCESS FLOW CHART
Figure 5: Process flow chart.
Galvanic Corrosion
Coupled weld specimen
Intrinsic Corrosion
Un-coupled weld specimen.
METHODOLOGY
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Sample Preparation
METHODOLOGY
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Test Parameters to investigate the weld segments corrosion behavior.
Parameters Test 1 Test 2 Test 3 Test 4
Brine 3 wt.% aqueous NaCl
Carbon Steel API 5L X52
Partial pressure (bar) 0.53
Temperature (OC) 80
Concentration of acetic acid (ppm)
0 0 1000 1000
pH 4 6.6 4 6.6
METHODOLOGY
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Method of Conduction
Method Measurements Connection Diagram
Linear Polarization Resistance (LPR)
LPR method will be used to measure corrosion rate between the weld samples.
Zero Resistance Ammeter (ZRA)
To measure the galvanic current of each weld region at specific time galvanic current density is performed.
METHODOLOGY
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Techniques of evaluationSample Techniques Results obtained Glass cell Connections
Un-coupled
Linear Polarization Resistance (LPR)
Intrinsic Corrosion sweep (mm/yr)
Current & Voltage / time Potential (mV) & Galvanic reading (mA/cm²)
Coupled Linear Polarization Resistance (LPR)
Galvanic Corrosion sweep(mm/yr)
Current & Voltage / time Potential (mV) & Galvanic reading (mA/cm²)
Zero Resistance Ammeter (ZRA)
]
Current weld measurement(mA/cm²)
Total corrosion [CRTotal = CRIntrinsic + CRGalvanic]
Total corrosion rate(mm/yr)
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Summary of intrinsic corrosion behavior of weld segments Intrinsic Corrosion Rate [mm/yr]
• Highest total corrosion rate of 0.13 mm/yr in Test 2.
• Least total corrosion occurred in Test 3; below 0.1 mm/yr.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Total corrosion rate of Heat Affected Zone
Discussion
• Highest total corrosion rate of 5.25 mm/yr in Test 3.
• Lowest total corrosion rate of 1.7 mm/yr in Test 2.
Total corrosion
rate(mm/yr) pH
HAc (ppm)
Test 1 3.8 4 0Test 2 1.7 6.6 0
Test 3 5.25 4 1000
Test 4 3.88 6.6 1000
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Test
Total corrosion
rateHAc
(ppm) pH
1 2.72 0 4
2 0.92 0 6.6
3 5.51 1000 4
4 2.06 1000 6.6
Total corrosion rate of Weld Metal
Discussion
• Highest total corrosion rate of 5.51 mm/yr in Test 3.
• Lowest total corrosion rate of 0.97 mm/yr in Test 2.
• Similar to the total corrosion rate pattern of HAZ.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Effect of pH influence
Test
Total corrosio
n rateHAc
(ppm)
1 2.72 0
2 0.92 0
3 5.51 1000
4 2.06 1000
• Test 1 corrosion rate is higher with pH 4 compared to Test 2 with pH 6.6.
• Increase in pH has lowered the corrosion rate by 66%.
• Test 3 has higher total corrosion rate with pH 4 compared to Test 4 with pH 6.6 with HAc present.
• The pH increment has mitigated the total corrosion rate by 62%.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Surface Morphology of pH effect comparing Test 1 and Test 2
Test 1 coupled specimen surface morphology of (a) parent steel, (b) HAZ and (c) weld metal after 24 hours LPR test under 1000x magnification.
Test 2 coupled specimen surface morphology of (a) parent steel, (b) HAZ and (c) weld metal after 24 hours LPR test under 1000x magnification.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Surface Morphology of pH effect comparing Test 3 and Test 4
Test 3 coupled specimen surface morphology of (a) parent steel, (b) HAZ and (c) weld metal after 24 hours LPR test under 1000x magnification.
Test 4 coupled specimen surface morphology of (a) parent steel, (b) HAZ and (c) weld metal after 24 hours LPR test under 1000x magnification.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Effect of HAc presence
Test
Total corrosio
n rateHAc
(ppm)
1 2.72 0
2 0.92 0
3 5.51 1000
4 2.06 1000
• Total corrosion rate of Test 3 has increased with the presence of HAc comparing Test 1 total corrosion rate without HAc present.
• Total corrosion rate has increased by 50% with the HAc presence.
• Test 4 total corrosion rate is higher with the presence of HAc compared with Test 2 without.
• Presence of HAc has increased the total corrosion rate by 55%.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Surface Morphology HAc presence comparing Test 1 and Test 3
Test 3 coupled specimen surface morphology of (a) parent steel, (b) HAZ and (c) weld metal after 24 hours LPR test under 1000x magnification.
Test 1 coupled specimen surface morphology of (a) parent steel, (b) HAZ and (c) weld metal after 24 hours LPR test under 1000x magnification.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Surface Morphology of FeCO3 thickness for Test 2 (without HAc presence)
Figure 34: SEM micrograph showing the cross section of the FeCO3 layer formed coupled sample under Test 2 experimental conditions. (a) parent metal surface;(b)
HAZ surface;(c) weld metal surface;(d) EDX results.
RESULTS AND DISCUSSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Surface Morphology of FeCO3 thickness for Test 4 (with 1000ppm HAc)
Figure 35: SEM micrograph showing the cross section of the FeCO3 layer formed coupled sample under Test 4 experimental conditions. (a) parent metal
surface;(b) HAZ surface;(c) weld metal surface;(d) EDX results.
CONCLUSION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
Analytical criteria
CRTotal Surface analysis Film Formation
Cross section film thickness
Test 1 3 (Corroded PM,HAZ) 3 WM
Test 2 4 (Protected) 4 PM, HAZ, WM Uniform Thin film formationHAZ>PM>WM
Test 3 1 (Corroded WM, HAZ) 1 PM
Test 4 2 (Corroded WM) 2 PM, HAZ Spots of thick film formation on PM surface.
No. Weightage1 Very High
2 High
3 Low
4 Very Low
• WM and HAZ highly affected by PWC in presence of HAc• pH influences the carbonate formation with and wihout
the presence of HAc• Presence of HAc causes corrosion rate to increase.• Low pH and HAc presence gives high corrosion rate
RECOMMENDATION
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
1. Identify the formation of the protective film that has formed on the
surface of the parent metal under low pH with HAc present.
2. Conduction of tests to investigate the HAc under varying temperature of
25oC and 60oC.
3. Investigate the formation of FeCO3 layer under different concentrations
of HAc such as 85 ppm and 850 ppm under constant pH of 6.6.
METHODOLOGY
Gantt Chart
▲Expected Milestones Table 4: FYP I Gantt Chart and Key Milestones
Background
Literature Review
Methodology
Results & Discussion
Conclusion & Recommendation
METHODOLOGY
Gantt Chart
▲Expected Milestones Table 5: FYP II Gantt Chart and Key Milestones
