ISO 21809-4:2009

INTERNATIONAL ISO
STANDARD 21809-4
First edition
2009-11-15
Petroleum and natural gas industries —
External coatings for buried or
submerged pipelines used in pipeline
transportation systems —
Part 4:
Polyethylene coatings (2-layer PE)
Industries du pétrole et du gaz naturel — Revêtements externes des
conduites enterrées ou immergées utilisées dans les systèmes de
transport par conduites —
Partie 4: Revêtements à base de polyéthylène (PE bicouche)

Reference number
©
ISO 2009
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©  ISO 2009
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ii © ISO 2009 – All rights reserved

Contents Page
Foreword .v
Introduction.vi
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Abbreviated terms .4
5 General requirements .4
5.1 Rounding.4
5.2 Compliance with this part of ISO 21809 .4
6 Information supplied by the purchaser.4
6.1 General information .4
6.2 Additional information .5
7 Coating classification .5
7.1 General .5
7.2 Coating systems.5
7.3 Coating thickness classes.6
8 Materials .6
8.1 Pipe .6
8.2 Coating materials .7
8.3 Packaging.9
9 Coating qualification .9
10 Application .10
10.1 General .10
10.2 Surface preparation.10
10.3 Pipe temperature .11
10.4 Application of adhesive .11
10.5 Application of polyethylene.11
10.6 Cutback.11
11 Inspection and testing .11
11.1 Inspection.11
11.2 Testing.11
12 Repair of coated pipe .14
12.1 Rectification of below-thickness coating.14
12.2 Repair.15
12.3 Stripping and recoating .15
13 Markings.15
13.1 General .15
13.2 Required markings .15
14 Handling and storage in the coating area.15
14.1 Handling .15
14.2 Storage .16
15 Test reports and certificates of compliance.16
Annex A (normative) UV ageing test and thermal ageing test.17
Annex B (normative) Cathodic disbondment test .19
Annex C (normative) Impact test .24
Annex D (normative) Indentation test .26
Annex E (normative) Flexibility test .27
Annex F (normative) Peel strength test .29
Annex G (normative) Peel strength test — Hanging mass .31
Bibliography .34

iv © ISO 2009 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21809-4 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries, Subcommittee SC 2, Pipeline transportation systems.
ISO 21809 consists of the following parts, under the general title Petroleum and natural gas industries —
External coatings for buried or submerged pipelines used in pipeline transportation systems:
⎯ Part 1: Polyolefin coatings (3-layer PE and 3–layer PP)
⎯ Part 2: Fusion-bonded epoxy coatings
⎯ Part 3: Field joint coatings
⎯ Part 4: Polyethylene coatings (2-layer PE)
⎯ Part 5: External concrete coatings
Introduction
It is necessary that users of this part of ISO 21809 be aware that further or differing requirements can be
needed for individual applications. This part of ISO 21809 is not intended to inhibit a vendor from offering, or
the purchaser from accepting, alternative equipment or engineering solutions for the individual application.
This can be particularly applicable where there is innovative or developing technology. Where an alternative is
offered, it is the responsibility of the vendor to identify any variations from this part of ISO 21809 and provide
details.
vi © ISO 2009 – All rights reserved

INTERNATIONAL STANDARD ISO 21809-4:2009(E)

Petroleum and natural gas industries — External coatings for
buried or submerged pipelines used in pipeline transportation
systems —
Part 4:
Polyethylene coatings (2-layer PE)
1 Scope
This part of ISO 21809 specifies the requirements for qualification, application, inspection, testing, handling
and storage of materials for plant application of two-layer polyethylene coatings (2-layer PE) applied externally
for the corrosion protection of bare steel pipe for use in pipeline transportation systems for the petroleum and
natural gas industries as defined in ISO 13623.
NOTE Pipes coated in accordance with this part of ISO 21809 are considered suitable for additional protection by
means of cathodic protection.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 31-0:1992, Quantities and Units — Part 0: General principles
ISO 62, Plastics — Determination of water absorption
ISO 306, Plastics — Thermoplastic materials — Determination of Vicat softening temperature (VST)
ISO 527-2, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and
extrusion plastics
ISO 527-3, Plastics — Determination of tensile properties — Part 3: Test conditions for films and sheets
ISO 868, Plastics and ebonite — Determination of indentation hardness by means of a durometer (Shore
hardness)
ISO 1133, Plastics — Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of
thermoplastics
ISO 1872-2, Plastics — Polyethylene (PE) moulding and extrusion materials — Part 2: Preparation of test
specimens and determination of properties
ISO 1183 (all parts), Plastics — Methods for determining the density of non-cellular plastics
ISO 4625-1, Binders for paints and varnishes — Determination of softening point — Part 1: Ring-and-ball
method
ISO 4892-2:2006, Plastics — Methods of exposure to laboratory light sources — Part 2: Xenon-arc lamps
ISO 8501-1:2007, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel
substrates and of steel substrates after overall removal of previous coatings
ISO 8502-3:1992, Preparation of steel substrates before application of paints and related products — Tests
for the assessment of surface cleanliness — Part 3: Assessment of dust on steel surfaces prepared for
painting (pressure-sensitive tape method)
ISO 8502-6, Preparation of steel substrates before application of paints and related products — Tests for the
assessment of surface cleanliness — Part 6: Extraction of soluble contaminants for analysis — The Bresle
method
ISO 8502-9, Preparation of steel substrates before application of paints and related products — Tests for the
assessment of surface cleanliness — Part 9: Field method for the conductometric determination of water-
soluble salts
ISO 8503-4:1988, Preparation of steel substrates before application of paints and related products — Surface
roughness characteristics of blast-cleaned steel substrates — Part 4: Method for the calibration of ISO surface
profile comparators and for the determination of surface profile — Stylus instrument procedure
ISO 8503-5:2003, Preparation of steel substrates before application of paints and related products — Surface
roughness characteristics of blast-cleaned steel substrates — Part 5: Replica tape method for the
determination of the surface profile
ISO 10474, Steel and steel products — Inspection documents
ISO 11124 (all parts), Preparation of steel substrates before application of paints and related products —
Specifications for metallic blast-cleaning abrasives
ISO 11125 (all parts), Preparation of steel substrates before application of paints and related products — Test
methods for metallic blast-cleaning abrasives
ISO 11357-6, Plastics — Differential scanning calorimetry [DSC] — Part 6: Determination of oxidation
induction time (isothermal OIT) and oxidation induction temperature (dynamic OIT)
ISO 13623, Petroleum and natural gas industries — Pipeline transportation systems
ISO 15512, Plastics — Determination of water content
ASTM D1693, Standard Test Method for Environmental Stress-Cracking of Ethylene Plastics
ASTM D3236, Standard Test Method for Apparent Viscosity of Hot Melt Adhesives and Coating Materials
SSPC-SP1, Solvent Cleaning
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
applicator
company that undertakes the coating application in accordance with the provisions of this part of ISO 21809
NOTE If the compounding of the top layer is done prior to or during the application process by the applicator, then he
is considered as manufacturer (see 3.7).
3.2
batch
quantity of coating material as defined by the manufacturer
2 © ISO 2009 – All rights reserved

3.3
batch certificate
certificate of analysis issued by the manufacturer
3.4
certificate of compliance
one of the types of documents defined by ISO 10474 that is issued in accordance with the purchase
requirements
3.5
cutback
length of pipe left uncoated at each end for joining purposes
3.6
holiday
coating discontinuity that exhibits electrical conductivity when exposed to a specific voltage
3.7
manufacturer
company responsible for the manufacture of coating material(s)
3.8
manufacturer’s specification
document that specifies the characteristics, test requirements and application recommendations for the
coating materials
3.9
maximum design temperature
maximum temperature that the coating can be exposed to during operation
3.10
pipe diameter length
any length along the pipe axis equal to the specified outside diameter of the pipe
3.11
pipeline
those facilities through which fluids are conveyed, including pipe, pig traps, components and appurtenances,
up to and including the isolating valves
[ISO 13623]
3.12
pipeline transportation system
pipeline with compressor or pump stations, pressure control stations, flow control stations, metering, tankage,
supervisory control and data acquisition system (SCADA), safety systems, corrosion protection systems, and
any other equipment, facility or building used in the transportation of fluids
3.13
purchaser
company responsible for providing the product order requirements
3.14
test report
document that provides the quantitative test results for tests conducted in accordance with the requirements of
this part of ISO 21809
3.15
test ring
sample taken from production coated pipe
4 Abbreviated terms
BST black standard temperature
ESCR environmental stress cracking resistance
MFR melt flow rate; designated as symbol q for use in mathematical expressions and equations
MFR
PE polyethylene
ppd per pipe diameter
SAW submerged arc welding
UV ultraviolet
2LPE 2-layer polyethylene coating
5 General requirements
5.1 Rounding
Unless otherwise stated in this part of ISO 21809, to determine conformance with the specified requirements,
observed or calculated values shall be rounded to the nearest unit in the last right-hand place of figures used
in expressing the limiting value, in accordance with ISO 31-0:1992, Annex B, Rule A.
NOTE For the purpose of this provision, the rounding method of ASTM E29 is equivalent to ISO 31-0:1992, Annex B,
Rule A.
5.2 Compliance with this part of ISO 21809
A quality system and an environmental management system should be applied to assist compliance with the
requirements of this part of ISO 21809.
NOTE ISO/TS 29001 gives sector-specific guidance on quality management systems and ISO 14001 gives guidance
on the selection and use of an environmental management system.
The applicator shall be responsible for complying with all of the applicable requirements of this part of
ISO 21809. It shall be permissible for the purchaser to make any investigation necessary in order to be
assured of compliance by the applicator and to reject any material and/or coating that does not comply.
6 Information supplied by the purchaser
6.1 General information
The purchase order shall include the following information:
a) the number of this part of ISO 21809 and year of publication (ISO 21809-4:2009);
b) pipe quantity, outside diameter, minimum wall thickness, minimum, maximum and nominal length; grade
of steel;
c) bare pipe standard or specification designation, e.g. ISO 3183;
d) coating system classification and thickness;
4 © ISO 2009 – All rights reserved

e) cutback length and tolerances for both ends of pipe;
f) pipeline maximum design temperature, in degrees Celsius;
g) test temperature for flexibility;
h) maximum cathodic disbondment radius at maximum design temperature.
6.2 Additional information
If applicable, purchase orders shall include the following information:
a) additional surface treatments;
b) plant inspection by the purchaser;
c) increased test-ring length;
d) test-ring location;
e) test frequency for additional test rings;
f) additional markings;
g) handling procedures;
h) storage procedures;
i) waiver of test reports;
j) other special requirements.
7 Coating classification
7.1 General
The coating shall consist of two layers:
a) 1st layer, composed of one of the following adhesives:
⎯ asphaltic modified rubber,
⎯ non-asphaltic-modified rubber (e.g. butyl based),
⎯ hot melt,
⎯ polymeric;
b) 2nd layer, consisting of the PE top layer.
7.2 Coating systems
The coating system shall be classified in accordance with Table 1.
Table 1 — Coating systems
Coating systems A B C
1st layer Asphaltic-modified rubber non-asphaltic-modified rubber hot melt or polymeric
adhesive adhesive adhesive
2nd layer PE PE PE
NOTE Temperature resistance of coating systems varies based on the polyethylene and adhesive systems specified.
7.3 Coating thickness classes
The total thickness of the coating shall be in accordance with Table 2.
Table 2 — Minimum total coating thickness
a,b
Coating thickness
Nominal pipe
mm
diameter
A B C
mm
minimum adhesive: 0,15 minimum adhesive: 0,2 minimum adhesive: 0,25
< 115 0,75 0,95 1,25
115 to 275 0,85 1,00 1,40
276 to 510 1,00 1,20 1,60
511 to 760 1,25 1,40 1,80
> 760 1,35 1,75 2,00
a
The total thickness may be reduced by a maximum of 10 % on the weld seam for SAW welded pipes.
b
The choice of coating thickness is dependent on the condition of the soil or ground, laying method onshore and offshore, service
constraints and pipe dimensions. These are minimum values and can be changed according to country or project specific requirements.

The applicator shall identify the materials and shall confirm that the certificates comply and relate to the
specified materials.
8 Materials
8.1 Pipe
The pipe being coated shall conform to the pipe standard or specification that is specified in the purchase
order.
CAUTION — Pipe conforming to such standards or specifications does not necessarily have a surface
condition that is appropriate for the application of coating, e. g. temporary coating, salt contamination,
slivers.
6 © ISO 2009 – All rights reserved

8.2 Coating materials
8.2.1 General
The applicator shall use materials that are
a) certified by the manufacturer as in accordance with the requirements of 8.2.2 and 8.2.3;
b) identified with the following:
⎯ manufacturer’s name,
⎯ product description,
⎯ mass of material,
⎯ batch number,
⎯ location of manufacture,
⎯ temperature and humidity requirements for transportation and storage,
⎯ the year, month and day of manufacture, and
⎯ expiry date;
c) handled, transported and stored prior to use in accordance with the manufacturer’s recommendations.
8.2.2 Adhesive
Each batch of adhesive shall be tested by the manufacturer in accordance with the requirements of Table 3 or
Table 4. Test results shall be reported in accordance with ISO 10474 and shall be made available to the
applicator on request. A batch certificate shall be provided by the manufacturer to the applicator.
Table 3 — Minimum requirements for adhesives in systems A and B
Properties Requirements Test method
A B
Viscosity Within 30 % of N/A ASTM D3236
manufacturer’s specification,
expressed in
millipascal·seconds
Specific gravity at 0,9 to 1,2 0,95 to 1,5 ISO 1183
(25 ± 3) °C
Melt flow rate N/A Within 20 % of ISO 1133
manufacturer’s specification,
expressed in grams per
10 min
Ring and ball softening point At least 20 °C above N/A ISO 4625-1
maximum design
temperature
Table 4 — Minimum requirements for adhesives in system C
Properties Requirements Requirements Test method
(hot melt) (polymeric)
Viscosity Within 20 % of N/A ASTM D3236
manufacturer’s specification,
expressed in
millipascal·seconds
Water absorption N/A ISO 62
< 0,1 %
Ring and ball softening point At least 20 °C above N/A ISO 4625-1
maximum design
temperature
Melt flow rate N/A Within 20 % of ISO 1133
manufacturer’s specification,
expressed in grams per
10 min
Moisture content N/A < 0,1 % ISO 15512
Vicat softening temperature N/A W 85 °C ISO 306
A/50 (9.8N)
8.2.3 Polyethylene
8.2.3.1 General
The applicator shall use polyethylene material that is in compliance with Table 5. Test results shall be reported
in accordance with ISO 10474.
Table 5 — Minimum requirements for polyethylene top layer
Properties Requirements Test method
a 3
Density of base resin W 0,930 g/cm ISO 1183
Melt flow rate at 190 °C: 2,16 kg Within 20% of manufacturer’s ISO 1133
specification
Elongation at break at 23 °C: ± 3 °C W 600 % ISO 527-2, ISO 527-3
b
Tensile yield strength at 23 °C: ± 3 °C W 10 MPa ISO 527-2, ISO 527-3
Vicat softening temperature A/50 W 95 °C ISO 306
(9,8 N)
Water absorption u 0,05 % ISO 62
Hardness Shore D W 45 ISO 868
ESCR (50 °C, F50, W 300 h ASTM D 1693
Cond. B, 100 % Igepal CO 630)
Oxidation induction time W 30 min at 210 °C, or ISO 11357-6
c
(intercept in the tangent method) W 10 min at 220 °C
d
UV resistance and thermal ageing ∆q W 35 % Annex A
MFR
a
The test specimen shall be a compression-moulded sheet annealed for 30 min at 100 °C
b
The test specimen shall be a 2 mm thick compression-moulded sheet prepared in accordance with ISO 527-2, strained at
50 mm/min. The specimen may also be prepared according to ISO 1872-2.
c
Manufacturer shall select one test condition only.
d
This test shall be performed only if UV additives have been included by manufacturer.

8 © ISO 2009 – All rights reserved

8.2.3.2 Compounding during processing
The polyethylene shall be compounded and stabilized by additives against UV and thermal ageing.
If the compounding is done by the applicator during the coating process, the applicator shall qualify the
process, conduct all the relevant tests versus the requirements of this part of ISO 21809, and shall certify that
the compounded polyethylene is in compliance with this part of ISO 21809.
8.3 Packaging
The coating materials shall be contained in packaging that is clearly labelled to identify the items specified
in 8.2.1 b).
For bulk shipments, where the container is not specifically marked for that product (e.g. railcars), the
manufacturer shall provide documentation to ensure traceability in accordance with the requirements of 8.2.1.
9 Coating qualification
The coating system shall be qualified by the applicator for each coating line.
Qualification shall be achieved by successful evaluation of pipe coated using the specified coating line. The
requirements for testing of pipe samples are given in Table 6. The qualification shall be repeated in case of
modifications to the coating line, application procedures or coating materials, including the following:
⎯ material composition;
⎯ change in manufacturer;
⎯ location of manufacturing.
Table 6 — Minimum requirements for coating qualification testing
Property Requirements for coating system Test method
A B C
Cathodic disbondment, 12 mm radius max. 20 mm radius max. 20 mm radius max. Annex B
28 days at 23 °C ± 3 °C
Cathodic disbondment, Purchaser’s Purchaser’s Purchaser’s Annex B
28 days at max. design specification specification specification
temperature
Impact resistance at > 3,0 J/mm > 3,0 J/mm > 3,0 J/mm Annex C
23 °C ± 3 °C
Indentation at Annex D
< 0,4 mm < 0,4 mm < 0,4 mm
23 °C ± 3 °C
Flexibility at No cracking of PE at No cracking of PE at No cracking of PE at Annex E
0 °C and/or −30 °C 2,5° ppd minimum 2,5° ppd minimum 2,5° ppd minimum
Peel adhesion at > 3,0 N/25 mm > 10,0 N/25 mm > 50 N/25 mm Annexes F or G
23 °C ± 3 °C
10 Application
10.1 General
A coating being applied during production shall have been previously qualified in accordance with the
requirements of Clause 9.
10.2 Surface preparation
10.2.1 Initial preparation
All dirt, deleterious matter and contaminants, such as oil and grease, shall be removed from the pipe prior to
coating. If necessary, pipe shall be cleaned in accordance with the requirements of SSPC-SP1.
All steel defects and irregularities (e. g. laminations, slivers, scratches) shall be removed by an approved
grinding method. Grinding of steel defects shall not reduce the wall thickness below the specified minimum
wall thickness of the pipe.
All pipe shall be dry prior to entering the abrasive blast cleaning unit(s). Pipe temperature shall be at least
3 °C above the dew point immediately prior to abrasive blast cleaning.
10.2.2 Abrasive blast cleaning
The abrasives used in the coating plant shall be in accordance with the requirements of ISO 11124.
NOTE If the pipe being coated is of a high-strength grade, e.g. L555, L690 or L839 (USC equivalents: X80, X100 or
X120, respectively) harder abrasives can be needed to provide the required cleanliness and surface profile.
The abrasives (including recycled materials) shall be maintained clean, dry and free from contaminants in
accordance with ISO 11125 so as not to contaminate the substrate.
For system A and B, the cleanliness achieved prior to application shall be in accordance with the requirements
of ISO 8501-1:2007, Grade Sa 2.
For system C, the cleanliness achieved prior to application shall be in accordance with the requirements of
ISO 8501-1:2007, Grade Sa 2½.
For systems A and B, the height of the surface profile attained shall be within 40 µm and 100 µm as measured
in accordance with the requirements of ISO 8503-4:1988, stylus method, or ISO 8503-5:2003, replica tape
method.
For system C, the height of the surface profile attained shall be within 50 µm and 100 µm as measured in
accordance with the requirements of ISO 8503-4:1988, stylus method or ISO 8503-5:2003, replica tape
method.
If grinding is required after blast cleaning, the maximum allowable area of grinding shall be 10 cm per metre
of pipe length.
10.2.3 Surface cleanliness
The surface cleanliness shall be measured in accordance with the requirements of ISO 8502-3:1992,
pressure-sensitive tape method. The maximum allowable level shall be Class 2.
10.2.4 Surface pre-treatment
If the applicator chooses a surface pre-treatment (e.g. deionized water or phosphoric acid pre-treatment), the
pre-treatment process shall be agreed with the purchaser.
10 © ISO 2009 – All rights reserved

If surface pre-treatment is used for qualification, it shall be used for production.
If surface pre-treatment is not used, testing for the presence of soluble salts on pipe shall be undertaken in
accordance with the requirements of ISO 8502-6 or ISO 8502-9. The maximum allowable level shall be
20 mg/m after blasting.
If high levels (above 20 mg/m ) of soluble salts are measured, a surface pre-treatment cleaning process shall
be agreed upon by the applicator and the purchaser.
10.3 Pipe temperature
Application temperature of the external pipe surface shall be as selected by the applicator within the
manufacturer’s recommendation.
10.4 Application of adhesive
The adhesive selected by the applicator shall be applied in accordance with the manufacturer’s
recommendation. The minimum adhesive thickness shall be as given in Table 2.
10.5 Application of polyethylene
The polyethylene may be applied immediately following the application of the adhesive to the pipe. The
minimum polyethylene thickness shall be as given in Table 2.
10.6 Cutback
The cutback length and tolerances on both ends of the pipe shall be as specified in the purchase order.
NOTE The polyethylene can undergo growth or shrinkage following cutback due to temperature change.
11 Inspection and testing
11.1 Inspection
If specified in the purchase order, inspection shall be undertaken by the purchaser. All inspections shall be
made at the place of application prior to shipment and shall be conducted without undue interference with the
operation of the plant. The purchaser may require that the applicator set aside pipe as requested for
inspection or testing, or both.
11.2 Testing
11.2.1 Incoming raw materials testing
The applicator shall conduct the sample preparation, testing and evaluation of the coating using suitable
equipment at the application facility.
The minimum testing frequency shall be one sample on every batch of coating materials received.
The properties of the adhesives shall be in accordance with the requirements of Table 7 or Table 4.
Table 7 — Incoming raw materials requirements for adhesive in systems A and B
Properties Requirements Test method
A B
Viscosity Within 30 % of manufacturer’s N/A ASTM D3236
specification, expressed in
millipascal·seconds
Melt flow rate N/A Within 20 % of manufacturer’s ISO 1133
specification, expressed in grams
per 10 min
Ring and ball softening At least 20° C above maximum N/A ISO 4625-1
point design temperature
The properties of the polyethylene shall be in accordance with the requirements of Table 8.
Table 8 — Incoming raw materials requirements for PE
Properties Requirements Test method
Melt flow rate Within 20 % of manufacturer’s ISO 1133
specification
11.2.2 In-process inspection / measurement by applicator
11.2.2.1 Surface finish
The surface finish shall be monitored and recorded a minimum of every 2 h during production to determine
whether the cleanliness is in accordance with the requirements of 10.2.3. Pipes that fail to conform to the
requirements shall be rejected and may be reblasted by agreement between purchaser and applicator.
11.2.2.2 Surface profile
At least once every 4 h of production, the external surface profile on two pipes shall be measured and
recorded using a profilometer, replicating film or purchaser-approved equivalent. The profile shall be in
accordance with the requirements of 10.2.2. Pipes that fail to conform to the requirements shall be rejected
and may be reblasted by agreement between purchaser and applicator.
11.2.2.3 Visual inspection
After cleaning, each pipe shall be visually inspected for surface defects and surface imperfections that can
cause holidays in the coating. Such surface imperfections shall be removed by grinding, provided that the
remaining wall thickness is within specified limits. Pipe containing surface defects shall be rejected or repaired
at the purchaser’s option.
11.2.2.4 Application temperature
The surface temperature of the pipe during the coating application shall be monitored and controlled within the
limits determined by the applicator.
Once the coating temperature is established, the temperature shall be monitored and recorded once every
hour.
Any change in the coating parameters, e.g. line speed, can necessitate a modification in the frequency of
temperature measurement.
12 © ISO 2009 – All rights reserved

11.2.2.5 Coating thickness
The total thickness and the thickness of the individual components shall be measured at four random
locations along the pipe at different circumferential positions, using a coating thickness gauge that has been
calibrated at least once every working shift (to a maximum of 12 h), and shall be recorded.
Such tests shall be conducted on each of the following, as applicable to the coating run lengths:
⎯ first pipe coated in the run;
⎯ one pipe from the subsequent lot of four pipes sequentially coated in the run;
⎯ one pipe from the subsequent lot of 10 pipes sequentially coated in the run;
⎯ one pipe from the subsequent lot of 35 pipes sequentially coated in the run; and
⎯ one pipe from the subsequent lot of 50 pipes sequentially coated in the run.
If the coated pipe does not meet the thickness requirements of 7.3, it shall be rectified in accordance with the
requirements of 12.1.
11.2.3 Holiday inspection
11.2.3.1 General
The entire coated surface of each length of pipe shall be inspected with a holiday detector having a search
electrode made of conducting material.
For inspection, the direct-current potential of the detector shall be set to exceed 10 V per micrometre of
nominal coating thickness, up to a maximum of 25 kV. The detector shall be calibrated at least once every
working shift (to a maximum of 12 h).
11.2.3.2 Acceptance criteria
No holidays shall be permitted in finished coating.
Pipe having less than three holidays shall be repaired in accordance with the requirements of 12.2. Any pipe
having three or more holidays, or a holiday having an axial length greater than 300 mm shall be stripped and
recoated in accordance with the requirements of 12.3.
11.2.4 Production test rings
11.2.4.1 Facilities
The applicator shall have suitable facilities available at the application plant for the preparation, testing and
evaluation of test ring samples for tests described in Table 9.
The applicator shall have the option of conducting the tests directly on the coated pipe or on cut test rings.
11.2.4.2 Test rings
Test rings shall be obtained from the end and shall be of sufficient size to provide the mandatory tests in
accordance with Table 9.
11.2.4.3 Testing requirements
The minimum test frequency of Table 9 shall be one test ring per pipe diameter every working shift (up to a
maximum of 12 h).
For pipe that is stripped and recoated, at least one test ring of the stripped and recoated pipe shall be taken
for each order item. If specified in the purchase order, additional test rings shall be taken.
Table 9 — Production coating testing requirements
Properties Requirements Test method
A B C
Cathodic disbondment: 12 mm radius max. 20 mm radius max. 20 mm radius max. Annex B
24 h, (65 ± 3) °C
Peel adhesion at (23 ± 3) °C > 3,0 N/25 mm > 10,0 N/25 mm > 50,0 N/25 mm Annexes F or G
Impact resistance at (23 ± 3) °C > 3,0 J/mm > 3,0 J/mm > 3,0 J/mm Annex C

11.2.4.4 Retests
11.2.4.4.1 If a test fails to conform to the specified requirements, either
a) the test that failed shall be repeated using two additional test samples taken from the originally tested end
of the affected pipe, or
b) all pipe coated after the previous acceptable test and prior to the next acceptable test shall be stripped
and recoated in accordance with the requirements of 12.3.
If both retests conform to the specified requirements, the coated pipe shall be accepted.
11.2.4.4.2 If one or both of the retests fail to conform to the specified requirements, either
a) all pipe coated after the previous acceptable test and prior to the next acceptable test shall be stripped
and recoated in accordance with the requirements of 12.3, or
b) subject to the approval of the purchaser, further retesting may be performed to determine which pipes
coated after the previous acceptable test are acceptable. Pipes that are not acceptable shall be stripped
and recoated in accordance with the requirements of 12.3.
12 Repair of coated pipe
12.1 Rectification of below-thickness coating
If required by 11.2.2.5, coated pipe that does not meet the thickness requirements but meets the requirements
of Table 9 may be overcoated by applying adhesive and polyethylene in accordance with the requirements of
10.4 and 10.5.
At least one production test ring shall be taken from the over-coated pipe during each 12 h working shift. The
test rings shall be prepared and tested in accordance with the requirements of 11.2.4. The peel adhesion
between the polyethylene layers shall be tested using the applicable method and acceptance criterion in
accordance with Table 9.
14 © ISO 2009 – All rights reserved

12.2 Repair
If required by 11.2.3.2 or 14.1, coated pipe shall be repaired in accordance with 12.2 and 12.3.
The repair shall be performed by the application of a compatible adhesive-lined heat-shrink sleeve, patch
material or melt stick.
If a sleeve or patch is used, the repair shall overlap at least 50 mm of the undamaged coating. If a melt stick is
used, the repair shall overlap at least 10 mm of the undamaged coating.
The repair material shall be applied in accordance with the manufacturer’s recommendations.
All repairs shall be holiday-tested in accordance with the requirements of 11.2.3.
12.3 Stripping and recoating
If required, all rejected coated pipe shall be stripped to bare metal and new coating applied in accordance with
the requirements of Clause 10.
The temperature during the stripping operation shall not exceed 275 °C.
The applicator shall record the identity of each stripped and recoated pipe.
13 Markings
13.1 General
Coated pipe shall be marked in accordance with the requirements of 13.2 and with any additional markings
specified in the purchase order. Additional markings as desired by the applicator shall be by agreement.
13.2 Required markings
The following markings shall be placed on the coating:
⎯ applicator’s name or mark;
⎯ number of this part of ISO 21809 and year of publication: ISO 21809-4:2009;
⎯ markings required by the applicable pipe specification or standard;
⎯ date of coating application; and
⎯ pipe number.
Marking shall be carried out using a method, such as stencil painting or printing, to ensure that the
identification is legible and indelible.
14 Handling and storage in the coating area
14.1 Handling
Coated pipe shall be handled in a manner that avoids damage to the pipe, pipe ends and coating. If specified
in the purchase order, the applicator shall submit details of the handling procedures; such procedures shall
include loading requirements where the applicator is responsible for loading.
Pipe that is damaged during processing shall be repaired in accordance with the requirem
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