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5349

Journal of Applied Sciences Research, 8(11): 5349-5359, 2012

ISSN 1819-544X

This is a refereed journal and all articles are professionally screened and reviewed

ORIGINAL ARTICLES

Corresponding Author: Mohamed A Wahab A Halim Gaber, Egyptian Petroleum Research Institute, 1 Ahmed El Zomer,

Nasr City, Cairo, Egypt.

E-mail: mgaber01@hotmail.com

Impact of Anti-Corrosion Liquid Epoxy and Fusion Bond Epoxy Primer on Mechanical

Testing of Three Layers Polyethylene Pipeline Coating

Gaber, M. AW.

Egyptian Petroleum Research Institute, Nasr City, Cairo, Egypt.

ABSTRACT

Pipeline coatings have undergone dramatic technological changes over the past two decades. Coatings now

must perform at higher in-service operating temperatures, must not be damaged in handling during construction

or in operation by soil stress or soil movement, and must provide exceptional corrosion protection. Coatings also

must be user friendly and must be able to be applied in a mill or in the field. This paper examines the

performance of liquid epoxy and fusion bond epoxy coatings on mechanical testing of three layer polyethylene

coatings pipeline which utilized in transport oil, gas and water. This study shall compare the on line and

laboratory inspection during surface preparation, preheat and application of 3layer extruded polyethylene

coating to determine which type of anticorrosion primer is more efficiency and durable for pipeline coatings.

The two types were applied for underground pipeline for Egyptian petroleum production companies since last

30 years at PETROJET coating plant. The field application testing indicates that the FBE primer give excellent

results for adhesion, cathodic protection, but the liquid epoxy primer give acceptable results but still less than

fusion bond epoxy.

Key words: polyethylene, cathodic protection, fusion bond epoxy, liquid epoxy primer, disbondment, 3layer

polyethylene.

Introduction

Pipelines are particularly important for the world, for their multi –uses and vital role in transporting

Petroleum and its products, as well as carrying water and drainage works. The pipelines are suffering from

corrosion, cracking and other problems. External corrosion has been recognized for many years as one of the

main deterioration mechanisms that may reduce the structural life of buried transmission pipelines. Corrosion of

these pipes inflicts huge costs on countries, to protect their pipelines, and make them workable for the longest

possible time. Ghazay El Metary (2004).

One of the ways followed in pipelines protection, is by coating them with special material that protect them

from affecting corrosion factors, as the type of the soil, moisture, pH, temperature variations and other factors.

Organic coating is used to control corrosion by isolating the external surface of the underground or submerged

pipeline from environment. This organic coating should have a high electrical resistance and high dielectric

strength to provide a barrier against moisture reaching the pipelines surface.

The pipelines are laid under buried environments over long distances from source to destination. In the

United States there are about 2 millions km of buried natural gas pipelines and 280,000 km of petroleum

products pipelines, which contributes billions of dollars to the economy. The growing demand and importance

for pipelines in all over the world warrants special attention to protect it from the deteriorating effects such as

corrosion, external forces and others. Among these effects, corrosion contributes the majority of the pipe failure

cases. For example, a recent review indicates that corrosion of metals and alloys costs U.S companies a total of

approximately $300 billion per year, these corrosion failures shall be eliminated by the use of best available

corrosion prevention techniques and materials.

1. Process of 3 Layer Polyethylene Coating:

Three layer polyethylene coating provides excellent corrosion protection, based on the use of a fusion

bonded epoxy or liquid epoxy primer with the mechanical protection afforded by medium or high density

polyethylene. Suitable for application on oil, gas and water pipelines at service temperatures up to 85°C, 3LPE

has an excellent track record. Anees U. Malik (1999).

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

Organic coatings, applied on properly pretreated surfaces, are the most common and most effective mode of

corrosion protection for metallic objects and structures. The exterior surfaces of corrodible metals such as iron

and steel are effectively protected from their environment by applying a coating system.

Despite the fact that the pipeline coating represents only about 5% of the total cost, the choice of the most

effective coating is a key point to guarantee the life of the installed pipelines.

A large variety of organic polymeric materials belonging to different functional groups has been used as

external coatings for open air or buried pipelines. Asphalt mastic and asphalt enamel, coal tar epoxy, extruded

polyethylene, fusion bonded epoxy, multilayer polyolefin coating systems including polyethylene or

polypropylene and polyurethane are some of the most widely used organic pipe coatings for external

applications. Polyethylene coatings having an FBE primer or liquid epoxy resin and a 2-layer polyethylene

based material extruded over it has been used extensively throughout the world in recent years BSI 96/.

The 3layers PE coating system applied to steel pipes shall be divided as follows:

-Layer 1: Immediately after the abrasive blast cleaning the layer shall formed by film of liquid epoxy resin

or fusion bond epoxy powder.

-Layer 2: This layer shall be formed by a polymer intended to provide adhesion between layer 1 and layer 3

and be compatible with those layers.

-Layer 3: This layer shall be formed by the polyethylene or polypropylene coating

Fig.1 Schematic of three layers Polypropylene coating for pipes

Fig. 1: Schematic of three layers Polypropylene coating for pipes.

3- Experimental & Field methodology:

The laboratory and field testing of bare pipes surface preparation, heating, priming, and

adhesive/polyethylene coating for pipelines used for oil/gas transportation were carried out on PETROJET, Port

Said and Suez coating plants.

The present study aims to find the effect of both liquid epoxy primer and Fusion Bond Epoxy as anti-

corrosion primers on mechanical testing of 3 layers polyethylene coating used.

The following inspection procedure and testing were carried out to find the efficiency of both types liquid

epoxy and FBE primers.

1- Climatic condition "temperature, relative humidity, dew point"

The climatic condition parameter is measured before start coating work to ensure that the ambient

temperature, relative humidity, dew point and steel surface temperature is suitable to apply the 3 layer

polyethylene coating for pipelines.

2- Measurement of rust grade of bare pipes

Rust grades of bare pipes are divided to 4 grades (A,B,C,D) according to degree of pitting in steel surfaces.

The grade of rust need to define before start surface preparation to determine the blasting method can be

achieve the cleanliness and profile degrees

3- Inspection of abrasive material (shot & grit)

Physical and chemical analysis for abrasive material shall be measured before used in blasting machine

4- Cleanliness degree

The cleanliness degree achieved by blasting shall be at least Sa 2½ according to ISO 8501-1

5- Surface profile

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

The surface anchor is necessary for good bonding of steel surfaces and coating materials and shall be

measured according to ISO 8503 -2

6- Salt level

The coated surface shall be free of all hazard materials " salt level" and shall be tested according to ISO

8502- 6

7- Dust level

Dust level for coated surfaces shall be less than rate 2 as per coating specifications and ISO 8502-3

8- Pipe preheat and coating materials

The preheating temperature of the steel pipes, adhesive and polyethylene coating materials shall be

measured at the frequencies to insure that the application temperature is comply with the manufacturer

recommendation.

9- Dry film thickness of primer, adhesive and PE

The coating thickness of the 3 layers coating system (primer, Adhesive, polyethylene) shall be measured

according to petroleum companies specification and DNV-RP-F106 (2011)

10- Adhesion test

The pipe coating requires sufficient adhesion to prevent water ingress or migration between the coating and

the pipe, along with cohesion to resist handling and soil stress. Soil stress is the main cause of pipe coating

failure. "Soil stress effects can be seen on flexible PE coatings with elastomeric adhesives as a

characteristic wrinkling. A.W. Peabody (2001).

The adhesion of the coating shall be determined by measuring the peel-off resistance in accordance with

DIN 30 670 at 23 & 80° C

11- Impact test

To protect steel from corrosion, a coating film must be continuous. Breaks in the coating will allow the

environment to permeate to the steel substrate and initiate corrosive degradation. The Impact test shall

performed by dropping a known weight from a calculated height onto the coating. Failure is the point at

which holidays were observed.

A Hot Spark or Holiday Test is then used to determine if the coating has been damaged or broken.

The objective of this test is to evaluate the resistance of the coating to damage from impact by a blunt ended

object. J Banach (2004), ASTM G 14 and DIN 30678.

12- Cathodic disbondment

Cathodic disbonment of anticorrosion primer is very important to ensure the performance of organic types

(liquid and FBE epoxies) and the testing procedure completed as per ASTM G8 & G42.

A- The coated carbon steel pipeline "X52" sample has been prepared for measurement of cathodic disbonding

after 2 day, maintaining at temperature of 65  2°C ). The sample has been cut from carbon steel pipeline

coated by POLYETHYLENE 3 Layer system, and the coating system includes the following layers :

1-Layer of Epoxy-based powder FBE, with DFT = 80 - 100 m.

2- Layer of ethylene-based polmeric adhesive with DFT = 330  m.

3- Layer of Polyethylene ( top coat ) with DFT = 2.5 mm.

B- The coated carbon steel pipeline "X52" sample has been prepared for measurement of cathodic disbonding

after 2 day, maintaining at temperature of 65  2°C ). The sample has been cut from carbon steel pipeline

coated by POLYETHYLENE 3 Layer system, and the coating system includes the following layers:

1-Layer of Liquid Epoxy primer, with DFT = 70 - 90 m.

2- Layer of ethylene-based polmeric adhesive with DFT = 330  m.

3- Layer of Polyethylene (top coat) with DFT = 2.5 mm.

13- Hot water test

The degree of coating to resistance disbondment due to hot water with NaCl solution 3% immersion shall

be tested in accordance with as per GBE/CW6:part 1. The coating shall show good resistance to

disbondment 80°C for 2 days

14- Flexibility test

Flexibility of steel coated panel to ensure the full coating system when exposed to external forces as per

CAN/CSA Z 245.20- 98

15- Degree of cure for fusion bond epoxy powder and liquid epoxy

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

The degree of cure shall be determined on layer 1 of the coating. The cure of fusion bond epoxy powder

shall be determined by differential thermal analysis and the acceptance criteria are based on the value of ∆

Tg in accordance to CSA Z 245.20. On the other hand the degree of cure of the liquid epoxy shall be

determined by measuring the hardness in accordance with IOS 2815.

16- Holiday test for coated pipes

The test measure the isolation of coating system to steel surface with high voltage at 25 k.v as per NACE

RP 0274

Results and Discussion

The following laboratory and online inspection were conducted in Petrojet coating plant, and includes the

following testing using calibrated equipments to ensure which type of both liquid and fusion bond epoxy

primers has been positively affect the adhesion and cathodic properties.

1- Climatic condition

The climatic condition parameter is measured before start coating work to ensure that the ambient

temperature, relative humidity, dew point and steel surface temperature is suitable to apply 3 layer polyethylene

coating for pipelines. Dew point less than steel temperature by 3°C.

Fig. 2: Hygrometer.

Fig. 3: Dew point & RH % calculator.

2- Rust grade of bare pipe before blasting

Rust grades of bare pipes are divided into 4 grades (A,B,C,D) according to degree of pitting in steel

surfaces, the rust grade of coated pipes used in this work is grade B which mean more or less presence of rust

traces "pitting" start to appear. The grade of rust need to define before start surface preparation to determine the

blasting method can be achieve the cleanliness and profile degrees.

3- Abrasive material (shot & grit)

Physical and chemical analysis for abrasive material measured before used in blasting machine and found

free from contamination and the conductivity is 140 uS/cm which comply with coating specification

requirements, Total Fina Elf (2002).

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

Fig. 4: Rust grade B.

4- Cleanliness degree

The cleanliness degree achieved by blasting is Sa 2½ to Sa3 according to ISO 8501-1.

Fig. 5: Blasted pipe to Sa 3.

5- Surface profile

The surface anchor is measured using the Press-O-Film gauge and it's necessary for bonding of primer with

steel surfaces and polyethylene coating layers, the profile ranging from 65- 80 um as per to ISO 8503 -2.

Fig. 6: Profile Gauge.

Fig. 7: Measuring profile.

6- Salt level

The coated surface shall be free of all hazard materials, the results indicates that the salt level is 1 um/cm²

"10 - 15 mg/m²" for both pipes coated with liquid and powder primers.

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

Fig. 8: Attach paper to substrate.

Fig. 9: SCM salt tester.

7- Dust level

Dust level for coated surfaces indicates no trace of contamination and less than rate 2 as per coating

specifications and ISO 8502-3.

Fig. 10: Transparent tape indicate no trace of contamination.

Table 1: Surface preparation of bare pipes parameters.

Test Liquid Epoxy Primer Fusion Bond Epoxy

Rust grade B B

Abrasive Shot/Grit Shot/Grit

Primer type Prodopeen coat 12-04 3 M

Cleanliness Sa 3 Sa3

Profile 65-85 65-85

Salt level 10 - 15 mg/m² 10 - 15 mg/m²

Dust level < rate 2 < rate 2

8- Pipe preheat and coating materials

The preheating temperature of the steel pipes, adhesive and polyethylene coating materials shall be

measured at the frequencies to insure that the application temperature is comply with the manufacturer

recommendation and the reading illustrated in table (2).

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

Fig. 11: Induction heat for pipe.

Fig. 12: temperature of coating materials.

Table 2: Preheat of pipe and coating materials.

Test Liquid Epoxy Primer Fusion Bond Epoxy

Pipe 195°C 205°C

Primer 75°C 180°C

Adhesive 215°C 215°C

PE 235°C 235°C

9- Dry film thickness of primer, adhesive and PE layers

The coating thickness of the 3 layers coating system (primer. Adhesive, polyethylene), were measured

according to petroleum companies specification on and the results recorded in table (3).

Fig. 13: DFT for fusion bond epoxy primer.

Table 3: Dry Film Thickness for coating layers.

Test Liquid Epoxy Primer Fusion Bond Epoxy

Primer 60-80 um 80-100 um

Adhesive 250 um 250 um

PE 2.5 mm 2.5 mm

10- Adhesion test

The adhesion of the coating shall be determined by measuring the peel-off resistance in accordance with

DIN 30 670 at 20° C and 80° C. The results of liquid epoxy primer is 80 kg/5 cm and 39 kg/5 cm consecutively.

5356

J. Appl. Sci. Res., 8(11): 5349-5359, 2012

The fusion bond epoxy powder results is 100 kg/5 cm at 20 ° C and 45 kg/5 cm at 80° C. Accordingly, the FBE

primer gives more bonding between substrate and coating layers and shall positively affect on corrosion

resistance and extend the pipeline shelf life.

Fig. 14: Adhesion (peel off) test.

Fig. 15: Bonding between PE & primer layers.

11- Impact test

Impact test for coated system according to DIN 30670 is carried out using an impact rod ≥ 5 J and the

holiday conducted over the impacted points and found no pin holes on both samples coated with both types of

primers

Fig. 16: Impact test for coated pipes.

5357

J. Appl. Sci. Res., 8(11): 5349-5359, 2012

12- Cathodic disbondment

Cathodic disbonment of anticorrosion primer is very important to ensure the performance of organic liquid

and FBE epoxies resistance to corrosion. The results obtained after 2 days at 65°C indicates that the fusion bond

epoxy powder increase in radial defect is 0.99 mm , but the Liquid epoxy primer increase in radial defect is

1.74 mm under the same condition, it means the performance and efficiency of FBE is more than Liquid epoxy

primer as per illustrated in table (4&5).

Table 4: Cathodic disbondment results of samples coated with Liquid epoxy primer.

ITEM Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 AVG.

INITIAL DIA. (mm) 6.00 6.00 6.00 6.00 6.00 6.00

FINAL DIA. (mm) 8.70 9.70 8.90 10.30 9.80 9.48

DISBONDING DIA (mm) 2.70 3.70 2.90 4.30 3.80 3.48

Max. Increase in Radial Defect (mm) 1.35 1.85 1.45 2.15 1.90 1.74

Table 5: Cathodic disbondment results of samples coated with Fusion Bond Epoxy primer.

ITEM Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 AVG.

INITIAL DIA. ( mm) 6.00 6.00 6.00 6.00 6.00 6.00

FINAL DIA. (mm) 7.43 7.77 7.70 8.33 8.63 7.97

DISBONDING DIA (mm) 1.43 1.77 1.70 2.33 2.63 2.44

Max. Increase in Radial Defect (mm) 0.72 0.88 0.85 1.17 1.32 0.99

Fig. 17: Cathodic disbondment.

Fig. 18: CD measurement.

13- Hot water test

The degree of coating to resistance disbondment due to hot water immersion shall be tested in accordance

with GBE/CW6: part 1. The fusion bond epoxy primer coating show no change in disbondment areas after

immersed in potable water at 80°C for 2 days. The liquid epoxy primer indicates increasing in disbonment area

with 16 %.

14- Flexibility test for FBE

The results indicate no visible cracks seen in coating layers when bending over a mandrel at ambient

temperature.

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

Fig. 19: Bending machine.

Fig. 20: Microscopic examination.

15- Cure of FBE

The degree of cure of fusion bond epoxy primer is tested using Differential Scanning Calorimetry (DSC) to

determine the glass transition temperature and the acceptance criteria ∆ Tg = -2/+3° C as per NACE RP 0394 ,

ASTM D 3895 and CSA Z 245.20. The glass transition temperature ∆ Tg (Tg2 – Tg1) results is 0.3 as illustrated

in Fig.(32). In case of Liquid epoxy primer the curing measured directly during application of primer over pipe

substrate and found dry and suitable for applying the subsequent 2 layers of adhesive and polyethylene.

Fig. 21: Cure graph.

Table 6: Mechanical testing for two types of primer.

Test Liquid Epoxy Primer Fusion Bond Epoxy

Adhesion at 20°C 80 kg/ 5cm 100 kg/ 5cm

Impact No crack No crack

Cathodic

Disbondment 0.99 mm 1.74 mm

Bend test No crack No crack

Hot water 1 mm No change or disbondment

DSC N/A ∆ g 0.3

Holiday no pinhole no pinhole

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J. Appl. Sci. Res., 8(11): 5349-5359, 2012

16- Holiday test for coated pipes

The test measure the isolation of coating system to steel surface with high voltage at 25 k.v and no pin holes

found in both pipes coated with liquid and FBE primers with polyethylene layers as per NACE RP 0274.

Conclusions:

-The bare pipes type is X52, climatic condition, rust grade, surface preparation (cleanliness, profile, salt

level, dust level), preheat parameters is the same for both types of organic anticorrosion liquid and FBE

primers.

-The adhesion test of fusion bond epoxy results is more than liquid epoxy primer as indicated in table (6).

-The cathodic disbondment test of fusion bond epoxy indicates small radial defect area (0.99 mm), than

liquid epoxy primer (1.74 mm).

-The FBE primer has good mechanical properties, low water permeation, no chemical degradation and good

corrosion resistance.

-3Layer polyethylene showed good resistance to water and chloride permeation.

-The present search recommends using the FBE primer with 3layer polyethylene coating system to achieve

the optimum cathodic protection and long shelf life of pipe coating.

References

ASTM G 8, 1996. Standard Test method for Cathodic disbanding of pipeline coatings.

ASTM G 42, 1996. Standard Test method for Cathodic disbanding of pipeline coatings subjected to elevated

temperature.

ASTM G 14, 1988. Standard Test method for Impact resistance of pipeline coatings (Falling weight test).

Peabody, A.W., 2001. Control of pipeline corrosion. NACE International.

Anees. U. Malik, Shahreer Ahmed, Ismail Andijani, 1999. Corrosion protection evaluation of some organic

coatings in water transmission pipes. Research & development center, Kingdom of Saudi Arabia.

Canadian Standards Association -CSA Z 245.20, 1998. External fusion bond epoxy coatings for steel pipe.

DIN 30 670, 1992. Polyethylene Coatings for Steel Pipes and Fittings, Requirements and Testing.

DIN 30678, 1992. Polyethylene coating for steel pipes.

DNV-RP-F106, 2011. factory applied external pipeline coatings for corrosion control. Item 7.2.8.

Gazay El Metary, Ms.C., 2004. Corrosion study and evaluation of externally coated pipelines. King Saud

University.

Gas Business Engineering (GBE CW6 part1): Technical Specification for the External Protection of Steel Line

Pipe and Fittings Using Fusion Bonded Powder and Associated Coating Systems.

ISO 8501-1, 1994. Preparation of steel substrate before application of paints and related products – Visual

assessment of surface cleanliness.

ISO 8503-2, 1988. Preparation of steel substrate before application of paints and related products – Surface

roughness characteristics of blast cleaned steel substrates.

ISO – 6, 1995. Preparation of steel substrate before application of paints and related products- Extraction of

soluble contaminants for analysis- the Bresle method.

ISO 8502-3, 1993. Preparation of steel substrate before application of paints and related products- Assessment

of dust on steel surfaces prepared for painting (pressure sensitive tape method).

ISO 2815, 2003. paints and varnishes – Buchholz indentation test.

J Banach, 2004. Liquid epoxy coatings for today's pipeline coating challenges. NACE International.

NACE –RP-0274, 2004. High – Voltage electrical inspection of pipeline coatings.

NACE –RP-0394, 2002. Application, performance, and quality control of plant-applied, fusion-bonded epoxy

external pipe coating..

Total Fina Elf, 2002. External protection of off-shore and related structures and equipment by painting, page 11.

ResearchGate has not been able to resolve any citations for this publication.

• A.W. Peabody

This manual is a collection of information on practices, techniques, materials and equipment, and related material on basic corrosion, cathodic protection theory, measurement practices, construction details and typical methods of installation and operation tested in field applications. (P.J.B.)

• J Banach

Pipeline coatings have undergone dramatic technological changes over the past two decades. Coatings now must perform at higher in-service operating temperatures, must not be damaged in handling during construction or in operation by soil stress or soil movement, and must provide exceptional corrosion protection. Coatings also must be user friendly and must be able to be applied in a mill or in the field. Liquid epoxies have been developed to provide protection for pipelines operating at temperatures up to 150°C. Additionally, adva nces to epoxy technology allow epoxy to be applied on wet surfaces and to bond to polyethylene coating systems.

Corrosion protection evaluation of some organic coatings in water transmission pipes

• U Anees
• Shahreer Malik
• Ahmed

Anees. U. Malik, Shahreer Ahmed, Ismail Andijani, 1999. Corrosion protection evaluation of some organic coatings in water transmission pipes. Research & development center, Kingdom of Saudi Arabia.

Corrosion study and evaluation of externally coated pipelines

• Ms C Gazay El Metary

Gazay El Metary, Ms.C., 2004. Corrosion study and evaluation of externally coated pipelines. King Saud University.

External protection of off-shore and related structures and equipment by painting

• Fina Total
• Elf

Total Fina Elf, 2002. External protection of off-shore and related structures and equipment by painting, page 11.

Corrosion protection evaluation of some organic coatings in water transmission pipes. Research & development center

• . U Anees
• Shahreer Malik
• Ismail Ahmed
• Andijani

Anees. U. Malik, Shahreer Ahmed, Ismail Andijani, 1999. Corrosion protection evaluation of some organic coatings in water transmission pipes. Research & development center, Kingdom of Saudi Arabia.

Source: https://www.researchgate.net/publication/281782594_The_15th_International_Conference_on_Petroleum_Mineral_Resources_and_Development

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