ISO/DIS 19277-1

ISO/TC 67

Secretariat: NEN

Date: 2026-01-14

Oil and gas industries including lower carbon energ — Qualification testing and acceptance criteria for protective coating systems under insulation —

Part 1:
Liquid applied coatings

Industries du pétrole et du gaz, y compris les énergies à faible teneur en carbone — Essais de qualification des systèmes de revêtement protecteurs sous isolation —

Partie 1: Revêtements appliqués sous forme liquide

DIS stage

© ISO 2026

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Contents

Foreword

Introduction

1 Scope

2 Normative references

3 Terms and definitions

4 Performance testing design

4.1 Relationship between artificial testing and natural exposure

4.2 Laboratory tests

4.3 Additional laboratory tests

5 CUI classification environments

6 Test specimens

6.1 Test specimens’ requirement

6.2 Steel substrates

6.3 Sampling of coatings

6.4 Number of test specimens

6.5 Coating systems

6.6 Scribe

6.7 Reference system

7 Test procedures and assessment

7.1 Assessment and acceptance

7.2 Assessment of adhesion and artificial ageing

7.3 Thermal cycling test

7.4 Method A - Multi-phase CUI cyclic corrosion test

7.5 Method B - Vertical Pipe Test

7.6 Method C – Test procedure as per AMPP TM21442-2023

8 Test report

(informative) Corrosion testing of conditioned and heat conditioned test samples

(informative) Example of test report for CUI coating acceptance

(informative) Example of test report for vertical pipe test

(informative) Optional Cryogenic Cycling Testing

Bibliography

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.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO [had/had not] received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 67, Oil and gas industries including lower carbon energy.

This second edition cancels and replaces the first edition (ISO 19277:2018), which has been technically revised. The main changes are as follows:

• Document has now been split into two parts; this document is Part 1 dealing with liquid applied coatings only, and Part 2 is dealing with tape and sheet applied products.
• Cryogenic cyclic test has now been moved from the standard text and is included in the Annex D (Informative).
• An additional CUI simulation test has been added and option included to perform one of the three listed test methods
• Tests on stainless steel specimens have been deleted. Qualification testing of coating system shall be carried out on carbon steel. The system is then also qualified for use on stainless steel.

A list of all parts in the ISO 19277 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

Unprotected carbon steel in insulated service with the presence of water and concentrating contaminants from the atmosphere or surrounding sources can cause accelerated corrosion and lead to severe metal loss. Additionally, unprotected austenitic and duplex stainless steels can suffer external chloride-induced stress corrosion cracking if contaminates, such as chlorides from the atmosphere and or the insulation, are present at the steel surface. Therefore, steel structures under insulation are normally protected to prevent corrosion-related damage during the operational life required of the equipment.

There are different ways of protecting steel structures from corrosion under insulation. This document deals with protection by use of coating when used as part of a system, including insulation and cladding materials, which can work together to prevent corrosion under insulation (CUI). All components of the corrosion prevention system are important in achieving adequate corrosion protection. This document only deals with the coating part of the corrosion protection system with focus on typical CUI coating environments. Further, this document focuses on accelerated testing protocols and acceptance criteria, so that interested parties can make informed decisions.

To ensure effective corrosion protection of steel structures and equipment, it is necessary for owners of such structures, planners, consultants, companies carrying out corrosion protection work, inspectors of protective coatings and manufacturers of coating materials to have at their disposal state-of-the-art information in a concise form on corrosion protection by coating systems. Such information has to be as complete as possible, unambiguous and easily understandable to avoid difficulties and misunderstandings between the interested parties with the practical implementation of protection work.

This document is intended to give the abovementioned information to people who have some technical knowledge of coatings and the process operations of the equipment. It is assumed that the user of this document is familiar with other relevant International Standards, particularly those dealing with surface preparation, inspection/testing of coatings, and relevant regulations.

Future parts of this document are to be developed which are to include other subjects like higher temperature, cyclic and intermittent service, testing of coatings for maintenance and repair, tape-applied coating materials, etc.

Oil and gas industries including lower carbon energ — Qualification testing and acceptance criteria for protective coating systems under insulation —

Part 1:
Liquid applied coatings

This document describes various corrosion under insulation (CUI) environments in refineries and other related industries and environments and establishes CUI environmental categories including operating temperature ranges from −45 °C to 204 °C for topside and aboveground service only. This document specifies both established and other test methods for the assessment of coatings used for prevention of CUI for each given environment. This document also provides acceptance criteria for each CUI environment.

NOTE The test results and acceptance criteria can be considered an aid in the selection of suitable coating systems. For service or peak temperatures over 204 °C testing acceptance criteria can be agreed between interested parties. Additional or other test and acceptance measures are possible but require particular agreement between the interested parties.

This document covers spray-applied coatings applied on new carbon steel for use in CUI service. The coatings can be used for new built structures and for existing structures where maintenance of the coating is needed. This document does not cover testing of sacrificial coatings, such as inorganic zinc, as these coatings can be consumed quickly in wet environments. Developing accelerated corrosion testing for what can be continuous wet service with sacrificial coatings is beyond the scope of this document.

“Non-through porosity” thermal spray aluminium coatings with greater than 250 µm dry film thickness can be tested and qualified in accordance with this document. This document does not cover tape and sheet applied products for use in preventing CUI.

This document does not deal with other aspects of coating degradation, such as those caused by abrasion, erosion, ultraviolet degradation or other methods that can exist given specific environment and construction methods.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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 554, Standard atmospheres for conditioning and/or testing — Specifications

ISO 1513, Paints and varnishes — Examination and preparation of test samples

ISO 2409, Paints and varnishes — Cross-cut test

ISO 2812-2, Paints and varnishes — Determination of resistance to liquids — Part 2: Water immersion method

ISO 4624, Paints and varnishes — Pull-off test for adhesion

ISO 4628-2, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 2: Assessment of degree of blistering

ISO 4628-3, Paints and varnishes — Evaluation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 3: Assessment of degree of rusting

ISO 4628-4, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 4: Assessment of degree of cracking

ISO 4628-5, Paints and varnishes — Evaluation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 5: Assessment of degree of flaking

ISO 4628-8, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 8: Assessment of degree of delamination and corrosion around a scribe or other artificial defect

ISO 7384, Corrosion tests in artificial atmosphere — General requirements

ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

ISO 12944-6, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 6: Laboratory performance test methods

ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling

ISO 19840, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Measurement of, and acceptance criteria for, the thickness of dry films on rough surfaces

AMPP TM 21442-2023, Test method for evaluation of protective coatings for use under insulation.

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at https://www.electropedia.org/

artificial ageing

procedure designed to accelerate the ageing of a coating system, i.e. to reduce the corrosion-protective efficiency more rapidly than by natural weathering

[SOURCE: ISO 12944-6:2018, 3.1, modified — ‘paint system’ has been changed to ‘coating system’.]

corrosion under insulation

CUI

corrosion that is a result of the effect of moisture and contaminants, on the steel surfaces under thermal insulation

dry film thickness

DFT

thickness of a coating remaining over the peaks of a rough surface when the coating has hardened

durability

expected life of a protective coating system to the first major maintenance coating

[SOURCE: ISO 12944-8:2017, 3.3, modified — ‘paint system’ has been changed to ‘coating system’ and ‘maintenance painting’ has been changed to ‘maintenance coating’.]

nominal dry film thickness

NDFT

dry film thickness specified for each coat or for the whole coating system

peak temperature

maximum temperature for the designed system, including possible upsets and temperature reached as a result of maintenance efforts such as steam cleaning

sacrificial coating

coating that provides corrosion protection by sacrificing or being consumed in the act of protecting the substrate

The selection of a coating system for specific conditions should preferably be based on experience from the use of the system in similar cases. The reason is that the durability of a CUI coating system depends on many external factors, such as the environment, the design of the structure, the insulation material, the weather proofing (cladding), the surface preparation, the application, drying procedures, service temperature, thermal shock, thermal cycling, peak temperature, amount of moisture, contaminants and other variables.

The durability is also linked to the chemical and physical characteristics of the system, e.g. the type of binder, the dry film thickness. These CUI related performance characteristics can be evaluated by artificial tests. Resistance to water or moisture, boiling water, steam interface, electrolytes in the system, thermal exposure, thermal shock, and thermal cycling are of primary interest.

Artificial tests and durations specified in this document have been selected to help ensure that potential coating systems will have the characteristics needed for the durability required in the intended service. Results from artificial tests should be used with caution, because artificial testing will not necessarily have the same effect as natural exposure. Many factors have an influence on the progress of degradation and, in the laboratory, it is not possible to accelerate all of them using the most effective method. It is therefore difficult to make a reliable ranking of coating systems of very different compositions from artificial tests in the laboratory. This can sometimes lead to efficient protective coating systems being rejected because they cannot pass these tests.

As CUI environments are very specific and have special requirements, several tests are included so that coating products can exhibit performance in harsh environments typical of CUI exposure. These include thermal performance, boiling water, thermal shock, thermal cycling, peak temperature performance, and long term isothermal conditions. In addition, these coating products shall provide corrosion protection for long periods of time at ambient conditions, and in possibly wet conditions related to initial coating application prior to process start up, time associated with process shutdowns, and short term mothballing of the facility.

Standard weathering testing procedures shall be used to establish ambient related corrosion control test procedures and acceptance criteria. Both air dried and conditioned test samples and heat conditions test samples shall be evaluated.

Additional CUI and high temperature related tests shall also be used in order to verify the ability of a coating to work under insulation at the prescribed conditions.

Inorganic zinc primers or other sacrificial coatings are no longer recommended in CUI environments due to the accelerated corrosion related to wet environments. If testing and acceptance is required, additional testing, as agreed between the interested parties, can be performed. However, long term wet environments are difficult to accelerate and as such the specifier/owner should be careful with any acceptance criteria for sacrificial coatings.

Other test methods may also be used by agreement between interested parties.

Table 1 provides a list of CUI classification environments including the minimum and maximum temperatures for all environments. These descriptions include both isothermal and cyclic conditions.

Table 1 — CUI classification environments

Further, each coating should be qualified for each specific CUI classification where it is intended to be used. A coating that meets the requirements of a CUI-1 classification does not necessarily meet the requirements of a CUI-3 classification, and a coating that meets the requirements of a CUI-3 classification does not necessarily meet the requirements of a CUI-1 classification. By consolidating testing some tests can be used for more than one classification.

For insulated service for temperatures above 204 °C, additional testing may be performed as agreed by interested parties.

This document requires the use of test specimens and other testing surfaces that are available as standard shapes typically available on the marketplace. Both A-36 or S275 carbon steel test specimens shall be incorporated in testing and also shapes as described in 6.2.1 to 6.2.4.

Test specimens will be as follows unless otherwise agreed to and documented.

Carbon steel test panels shall be made of A-36 or S275 carbon steel. The minimum panel size shall be 3 mm × 150 mm × 70 mm or as agreed and documented by the parties. The thickness of the test panels shall not allow for bending as a result of heating and quenching. Unless otherwise agreed, the panel surface shall be prepared by abrasive blast-cleaning to meet the requirements of the corresponding technical product data sheet as per the coating manufacturer’s instructions. In all other respects, test panels shall comply with ISO 7384.

Square carbon steel tubing (A-36, ASTM A-500, or S275) ASIC standard shape HSS4X4X1/4 measuring approximately 101,4 mm by 101,4 mm, 406,3 mm long with a wall thickness of 6,35 mm shall be used for the multi-phase CUI cyclic test. Each coating sample area shall be a minimum of 101,4 mm long, on all four sides of the square tube with just the front face scribed with an X-cut. Each tube shall have an endcap welded on each end with a 25,4 mm pipe 101,5 mm long with a threaded connector. The two pipes shall be centred horizontally and shall be vertically attached with a centre 25,4 mm down from the top of the square tube. The completed tube should be tested to ensure that the welds do not leak. Figure 2 provides a general layout (see 7.4.2). Unless otherwise agreed, the tube’s exterior surfaces shall be prepared by abrasive blast-cleaning to meet the requirements of the corresponding technical product data sheet as per the coating manufacturer’s instructions.

A standard black carbon steel pipe (A-36 or S275), approximately 600 500 mm long, with 50 mm outside diameter with typical wall thickness of 45 mm shall be used for the vertical insulation pipe test. Unless otherwise agreed, the test surface shall be prepared by abrasive blast-cleaning to surface preparation to meet the requirements of the corresponding technical product data sheet as per the coating manufacturer’s instructions.

The pipe spools shall be made of commercial grade low carbon steel (A-36 or S275). Multiple test specimens of each system being tested should be prepared. A minimum of two (2) test specimens is recommended. However, the use of single specimens would be valid if accepted by the end-user. The length of each pipe spool shall be between 15 cm (6 in) and 30 cm (12 in). Unless otherwise agreed, the test surface shall be prepared by abrasive blast-cleaning to surface preparation to meet the requirements of the corresponding technical product data sheet as per the coating manufacturer’s instructions.

A representative sample of the product to be tested (or of each product in the case of a multi-coat system) shall be taken in accordance with ISO 15528. Each sample for testing shall be examined and prepared in accordance with ISO 1513.

At least three specimens shall be prepared for each test, unless otherwise specified. Testing should be done in triplicate.

The test specimens/surfaces shall be dry and free of dust, grease and any other foreign matter, immediately prior to coating application and in keeping with the coating manufacturer’s recommendations. The test specimens/surfaces shall be coated (preferably by spraying), air dried and cured in strict accordance with the coating manufacturer's recommendations. Each coat shall be homogenous in thickness and appearance and free from runs, sags, misses, pinholes, wrinkling, gloss variation, cissing, particle inclusions, dry overspray and blistering. If the manufacturer's drying requirements are in conflict with 6.5.4, the requirements of 6.5.4 shall take precedence, unless agreed to by all parties. Appropriate protection shall be applied to the edges and back side of test specimens.

The method and procedure for checking dry film thickness shall be in accordance with ISO 19840 for rough surfaces. After each coat is sufficiently hardened, the dry film thickness of the applied coating shall be measured on the test surface of the test specimen/surface at five locations (in the centre and each corner, at least 15 mm to 20 mm from the panel edge or rounded surface of the square tube) and these measurements shall be recorded as the minimum, arithmetic mean and maximum. Dry film thickness values for each coat shall be in accordance with ISO 19840 for both individual readings and average DFT. Maximum DFT shall never exceed 1,25 x NDFT, both for each coat and with respect to total DFT. If NDFT of any coat is ≤60 µm, max DFT shall never exceed 1,5 x NDFT.

For each layer of coating application, the overcoating interval shall comply with the coating manufacturer's recommendations.

Unless otherwise agreed, the coated test samples shall be conditioned for three weeks in a standard atmosphere of 23 °C ± 2 °C with 50 % ± 5 % relative humidity, before testing, and in accordance with the requirements of the corresponding technical product data sheet as per the coating manufacturer’s recommendations.

Heat conditioning of the test samples shall be performed on applied and conditioned test samples. Heat conditioning shall consist of heating the conditioned test specimens to the maximum temperature of the classification for 20 h in a muffler oven or other similar device. The test specimens shall then be removed and air cooled for 4 h. This process shall be repeated a total of 5 times, providing for a total of 100 h exposure at maximum temperature of the classification and 20 h of air-cooling time.

If a scribe is required for testing of coatings on steel substrates, the scribe shall be in accordance with ISO 12944-6. Special care should be taken to ensure that potentially hot and small metal fragments do not affect the sample. Individual test procedures will indicate the need of a scribe for testing.

For the multi-phase CUI Simulation test as described in section 7.4 alternative guidelines for the required scribe should be used.

It is recommended to use a coating system that has been in successful use for years on site and whose performance as indicated by laboratory testing is well known, as a reference system. This system shall be as similar as possible in composition and/or generic type and dry film thickness to the coating system being tested.

All tests shall be conducted in triplicate. At least two of the three tests shall comply with the requirements specified in this document. For CUI simulation testing only one of the three documented test methods shall be carried out and included in the test report. CUI simulation test method choice should be agreed between parties. Triplicate for the multiphase CUI cycle test shall be three separate tubes run in three separate test cycles. Triplicate for the vertical pipe test shall be three separate tubes. Triplicate for the AMPP 21422 CUI test shall be three separate tubes.

The applied and conditioned coating sample specimens and the heat conditioned coating sample specimens shall be tested for adhesion. This includes the carbon steel test specimens. Table 3 provides list of testing and acceptance criteria.

Table 3 — Adhesion assessment before artificial ageing for carbon steel test specimens

Table 4 provides test methods and durations as required for each classification. Table 5 provides acceptance criteria for these tests. Annex A provides a rationale for the testing of ambient and heat conditioned test specimens.

Table 4 — Ambient test methods and duration for carbon steel test specimens

Table 5 — Ambient corrosion test acceptance criteria

The artificially aged test specimens shall be tested for adhesion after the prescribed duration (time of assessment) in the standard atmosphere in accordance with ISO 554. This includes only the carbon steel test specimens. Table 6 provides a list of testing and acceptance criteria.

Table 6 — Adhesion assessment after ambient corrosion testing for carbon steel test specimens

The test specimens are placed in the oven and heated. When the test specimen reaches the maximum temperature of the classification, it shall immediately be dipped/quenched into ice water covering at least 3/4 of the test specimen and left immersed until the temperature of the test sample metal temperature is reduced to <15 °C. This shall be repeated for the number of cycles required. The coated surface shall then be evaluated. Minimum and maximum thermal cycling temperatures and the number of cycles are provided for each CUI classification in Table 7. Acceptance criteria are provided in Table 8.

Table 7 — Thermal cycling test for carbons steel test specimens

Table 8 — Thermal cycling acceptance criteria

The multi-phase CUI cyclic corrosion test process is used to test the ability of the coating to work in typical environments where CUI occurs. This test process includes dry heat, thermal shock, immersion, boiling water, steam interface, and shut down time. This test takes six weeks and does not consider the effect related to individual insulation materials. This test process is used for CUI-2 and CUI 3, as these CUI coatings extend into the boiling water range.

The multi-phase cyclic CUI test method is designed to provide an overall test procedure for coatings for elevated temperature insulated service. It includes cyclic testing methods providing dry heat, intermittent boiling water for an extended period of time, a steam interface, and an ambient state where there is no heating.

This test process does not take into account the effect of any possible detrimental chemicals given off by specific insulation materials. The immersion and boiling water portion of this test utilizes water with 5 % NaCl (m/v).

To understand the effect of any chemicals associated with the use of any particular insulation, a specific solution can be agreed between the interested parties. Any change of solution shall be documented in the final report.

Figure 1 provides an overall schematic diagram of the equipment and guidance as to the test set up.

Key

1 sample tube

2 steam port

3 view port

4 chamber lid

5 closed loop oil heater or other alternate heating mechanism

6 solution chamber

7 auxiliary heater

8 peristaltic pump

9 solution chamber

Figure 1 — Schematic presentation of multi-phase CUI cyclic corrosion test

The apparatus includes the following items.

1. Closed-loop oil heater with piping of approximately 2,54 mm internal diameter connecting to the CUI sample tube. The heating unit should be capable of keeping the circulating heating oil at the specified testing temperature. The heater is typically three phases with 6 kW heating capacity. Alternate heating systems are acceptable, if the temperature of the surface of the sample tubes is maintained with ±5 °C.
2. Closed-loop heat transfer fluid/oil for operating to the maximum temperature of the test in the range of 150 °C to 175 °C can be used.
3. CUI sample tube, coatings applied and conditioned in accordance with 6.5.4. Figure 2 provides a schematic presentation of the CUI sample tube. Each coating tested shall have a least a 100 mm wide continuous application on all four sides of the tube.
4. Solution chamber and lid with view port and with four 6,35 mm ports: three for steam release and one for tubing connection from the peristaltic pump. Figure 3 provides a schematic presentation of the solution chamber.
5. Peristaltic pump for pumping the solution to the solution chamber with tubing for transfer of the solution.
6. Auxiliary hot plate heater typically two heater 220 V – 240 V, 5 kW, with approximate dimension 375 mm × 625 mm.

^a Centred.

Figure 2 — Schematic presentation of sample tube (square pipe)

Key

A loose fit hole for 25,4 mm (1 inch) pipe fitting centred on both ends

B solution chamber lid weldment

C solution chamber weldment

D tabs for centring lid on chamber

NOTE Components are weldments made using 3,175 mm non-rusting material suitable for temperature of test protocol. Watertight welds with loose fit between solution chamber and lid.

Figure 3 — Schematic presentation of solution chamber

The applied and conditioned CUI sample coated tube shall be scribed in accordance with 7.4.3.1 on the face of the square tube as depicted in Figure 2. Note that the pipe fittings are welded offset in one direction. The CUI sample tube should be piped to the closed-loop oil heater using a section of flexible (typically flexible for ease of assembly) stainless tubing to each side of the CUI sample tube.

The solution chamber shall be placed on the auxiliary heater. The CUI sample tube should be placed in the solution chamber with the offset hanging down, so that during the immersion phase the solution will reach the midpoint of the scribe face/side. The CUI sample tube should not be in contact with the bottom or sides or top of the solution chamber. The solution chamber lid shall be placed within the clips of the solution chamber.

The peristaltic pump shall be connected with one of the four steam vents to allow a predetermined amount of solution into the solution chamber.

Scribe preparation

The suitable length of the scribes crossing in a 90° angle shall be 100 mm as it should give an overview what happens on the surface of the system. Too short scribing lengths have an impact on the results. The intersection of the scribes is to be ignored in the evaluation. The width of the scribe mark is determined to be 1 mm

The cross-section of the scribe mark should be as uniform as possible along its entire length. The coating should be cut smoothly along the direction of the scribe mark. The cross-sectional shape of the scribe may be either “V” or “U” shaped, depending upon the tool used, and should be such that for a “V”- shaped cut a > b > c and for a “U”-shaped cut a > b, with the width (b) of both “V” and “U” shapes such that b > 0,2 mm. Refer to ISO17872 for tools and methods that can be used.

Key

1 coating

2 substrate

a width of scribe mark at surface of coating

b width of scribe mark at coating/substrate boundary

c width of scribe mark at maximum penetration into substrate

d penetration of scribe mark into substrate

Figure 4 — Schematic of scribe preparation

The test procedure shall be in accordance with the following cycle.

1. The tube shall be heated, internally, to the test temperature by heating the oil in the closed-loop oil heater to a temperature that results in the surface of the coated tube reaching 150 °C ± 5 °C or 177 °C ± 5 °C, depending on requirement. The surface temperature of the coatings samples on the square tube will reach test temperature within 30 min to 60 min.
2. The oil temperature shall remain at set temperature throughout the heating process, which shall last for 120 h each week. The initial heating processes each week will take 30 min to 40 min depending on test temperature requirements. The oil heater will be initially set to 93 °C and once it comes to temperature, left to stabilize for 10 min. The temperature setting is then increased to150 °C and left to develop steady state for 10 min. The heater will then be adjusted to 175 °C as can be required for CUI-3.
3. After 4 h of the initial dry cycle, the predetermined amount of liquid test media [distilled or deionized water with 5 % NaCl (m/v)] shall be pumped into the enclosure to height where the bottom of the tube is covered on the bottom and up to a height of 50 mm. The peristaltic pump setting and tube selection shall be selected to deliver the solution within 3 min to 4 min. Actual fluid pump rate and volume should be established for each solution chamber size and assemble before the first actual test cycle. This is the initial immersion boiling water cycle.
4. With the heat supplied by the heated tube sample as well as the auxiliary heater below the enclosure, the water should boil and evaporate and leave the chamber dry between 3 h and 15 min and 3 h and 45 min. The water will boil vigorously, and the water level will evaporate quickly so that typically the tube is no longer immersed after one hour. Adjustment of auxiliary heater set point temperature can be required to adjust the evaporation time frame.
5. The chamber shall then be left to run dry and hot for 4 h.
6. This shall be followed by a wet cycle using distilled water only for 4 h. The remaining immersion boiling water cycles within the 120-hour period shall be with distilled water only, so as not to build up the concentration over 5 % NaCl (m/v).
7. These 8 h cycles shall be repeated for the duration of 120 h or 5 d. The last of these cycles will be a wet cycle that shall finish dry.
8. The oil heater and the auxiliary heater are shut off for 48 h, representing a standard process shutdown. The tube should be removed, and the interior of the chamber and the exterior of the tubes should be rinsed with tap water (squirt bottle, faucet, and/or garden hose) to remove any visible salts, rust or other materials from the chamber. The tube and chamber are left unheated for 48 h. The processes in steps 1) to 8) run again for the next 7 d and then repeated for a total of 6 times.
9. After 6 weeks of testing is completed, the tube shall be thoroughly cleaned and prepared for immediate evaluation within 24 h of completion of the test.

Table 9 provides the criteria for the multi-phase cyclic CUI test setup.

Table 9 — Multi-phase cyclic CUI test criteria for carbon steel tube test samples

The sample surface shall be evaluated as soon as possible on the top face (condensation face), scribe face (immersion and steam interface) and the bottom, including the curved corners (intermittent immersion surface). Edges that are 15 mm from the end of the tube, or adjacent to other coatings applications, shall be disregarded. Table 10 provides the acceptance criteria for the multi-phase cyclic test.

Table 10 — Acceptance criteria for multi-phase cyclic test

The vertical pipe test is one of three alternative test methods contained within this document. The Vertical Pipe Test is designated as Method B.

The vertical pipe test has been designed to test the resistance of coatings to accelerated CUI conditions including ingress of salt solution into the insulation, temperature cycling to temperatures designated by the CUI classification chosen as well as periods of “shutdown” where the pipe cools to ambient temperature.

Figure 4 provides an overall schematic diagram of the equipment and guidance as to the test setup. A general layout of the equipment needed for setting up the vertical pipe/insulation test is as follows:

1. 3 x coated carbon steel pipes length 600 mm, diameter 60 mm and wall thickness 5 mm with a welded strip of metal attached to the top to allow easier handling of the pipe.
2. Ceramic hotplate with a maximum operating temperature of 500 ºC which can achieve the temperatures required by the CUI category chosen for test.
3. Light weight calcium silicate pipe insulation suitable for Corrosion under Insulation exposure according to ASTM C1617, (500 mm x 60 mm inside diameter and 50 mm thick) covered with aluminium foil or another metallic barrier to prevent drying out during the test.
4. Leaf thermocouple sensors applied on the hotplate and at 50 mm intervals along the pipe length to measure real time surface temperatures during the test. 11 sensors will be required for a 600 mm test piece and should be compatible with the temperature range to be tested and resistant to moisture exposure. Create slots to feed he thermocouple sensor wires through the insulation at the correct spacing and secure with multiple cable ties to ensure the shells and thermocouple sensors are held tightly in place.
5. Stainless steel or Teflon coated steel pan of suitable dimension to collect excess salt solution elutes from the insulation during the test.
6. Datalogger to measure and record temperatures provided by the sensors installed of the test pipe.
7. Digital thermometer to measure ambient laboratory temperatures during the CUI test.

Key

1 hotplate

2 carbon steel pipe

3 foil covered insulation

4 surface temperature thermocouple probes

5 datalogger

6 stainless steel pan

7 recessed trough for salt solution addition

Figure 5 — Vertical Pipe Test Setup

Testing shall be carried out in triplicate on coated carbon steel pipes of length 500 mm, outside diameter 60 mm and wall thickness 5 mm. Measure and record the dry film thickness of each of the test pieces as described in Appendix B of this document. The pipe shall be insulated with ASTM C533 Type 1 calcium silicate insulation of 600 mm length, 60 mm inside diameter and thickness 50 mm covered with an outer layer of aluminium or metallic foil to prevent drying out during the test.

The Vertical Pipe test is designed to provide an accurate record of the exposure temperature the test pipes experience during the CUI simulation test. As with the other methods described within this document, introduction of salt solution into the system depresses the temperature experienced. Daily recording of test temperatures and the nature of the reporting templates within Appendix D will give a clear indication of minimum and maximum temperatures for each surface sector tested and assessed.

The pipe should be evaluated as follows.

1. Place the insulated pipe in a stainless-steel pan or other vessel of sufficient size to capture surplus salt solution during the test. Place the pipe and pan on the hotplate and pour** 800 millilitres of 1 % (w/v) NaCl into the recessed trough in the top face of the insulation. Introduce the solution gradually so that it does not exceed the capacity of the trough and spill down the sides of the insulation and pipe. Continue this process until all the salt solution has been absorbed by the insulation. Leave the pipe to stand for 10 minutes.
2. Switch on the hotplate and set to the required temperature
3. Heat the pipe for 8 h. Measure the temperature of each of the thermocouple probes and record it noting the cycle number, and temperature on the sheet given in Appendix D of this document.
4. Switch off the hotplate and pour** 800 millilitres of 1 % NaCl (w/v) into the insulation following the same instructions as outlined in 1) above. Allow the pipe, insulation, insulation and pan to cool, whilst still on the hotplate, to laboratory ambient temperature for 16 hours.
5. Repeat the cycle above for 5 days per week for 6 weeks (total 30 cycles)
6. Evaluate coating degradation as outlined in Appendix C post-test assessment such that there will be a defect assessment for each of the 36 sections of the pipe surface identified. Disregard any corrosion related to damages from siting of thermocouple probes on the pipe surface. Record the results in the sheet provided in Appendix C of this document and make a recommendation of pass/fail based on Table 15 below.

**Salt solution may be added manually into the recessed trough within the insulation, or an automated method can be used to administer the solution at a suitable rate to avoid overflow and loss.

Table 15 provides the acceptance criteria. To satisfy the requirements of the standard, 2 out of the 3 pipes would need to meet this level of performance.

Table 15 — Vertical pipe test acceptance criteria

The test procedure as per AMPP TM21442-2023 Method C has been designed to test the resistance of coatings to accelerated CUI conditions within the CUI temperature range -4 °C to 175 °C.

with the inclusion of ingress of salt solution into the insulation (Type 1 calcium silicate confirming to ASTM C533), temperature cycling to temperatures designated by the CUI classification in table 16. The test uses pipe specimens that are coated and insulated following the instructions of the manufacturer or end-user.

To simulate and accelerate the breakdown of the insulation system, holes are drilled in the 6 ‘o’ clock position i.e. on the bottom of the insulation jacketing, allowing ingress of the test solution. Pipe spools are placed horizontally in a vessel or trough which allows for the introduction of an electrolyte. A minimum of five cycles should be used during a typical work week. All details of the test set up and conditions can be found in the AMPP TM21442-2023 document.

Key

1 insulation jacketing

2 insulation

3 coated pipe section

4 water

5 trough for Water

6 heat Input

7 heat outlet

Figure 6 — Sample Configuration for AMPP TM21442 CUI test

Table 16 — AMPP TM21442 CUI Test Acceptance Criteria

The test report shall contain at least the following information:

1. the test laboratory (name and address).
2. the start and completion date of each test
3. a description of the substrate and substrate surface preparation.
4. all details necessary to identify the protective coating system (manufacturer, names or reference numbers of the products, batch numbers, numbers of coats, dry-film thickness for each coat)
5. the duration and conditions of drying/curing and conditioning.
6. details of the temperature profile calibration including target temperature, temperature readings for each profile calibration and used equipment references. Calculate variance of profile calibration temperatures versus +/- 5 % temperature variance limit.
7. Post-test assessment sheet for each test pipe including pipe level position, Pass/Fail criteria versus each of the ISO 4628 Parts 2-5, maximum and minimum temperature exposure for the pipe level position and average total dry film thickness.
8. the tests carried out and the duration of each test.
9. the results for each test specimen.
10. any deviation from the test methods specified.

The test report shall explicitly state that the test equipment and procedure were in accordance with the relevant ISO standard.

The test report shall be signed by the person performing the tests and by the laboratory manager or by another authorized representative of the laboratory. Examples of test report forms are given in Annexes B to C.

1. 
   (informative)
   
   Corrosion testing of conditioned and heat conditioned test samples

The rationale behind selection of corrosion testing methods, duration and acceptance criteria is taken in part from ISO 12944-1, ISO 12944-2 and ISO 12944-6. The ISO 12944 series describe test methods, durations and acceptance criteria for coatings for typical atmospheric service. ISO 12944-1 describes three durability ranges based in years until first maintenance. ISO 12944-2 describes classifications of environments based on various ambient environments based on typical corrosion rates. ISO 12944-6 describes testing and acceptance criteria.

For corrosion testing within this document, two conditions for the coating exist because of the heated and insulated environment.

• Condition 1

This condition would be that the coatings are as applied and have not gone through a heating cycle. This condition would be found as part of a new construction project, where the coatings are applied at some stage of fabrication and construction of the facility and then may not be put into service for a short to extended period, depending on the construction schedule. With the complexity and size of modern construction this could extend to multiple years.

A C5 environment and IM-3 (for immersion risk) with high durability life were selected for evaluating coating performance for this condition.

• Condition 2

This condition would be that the coatings have been applied and put into service\heated and then the thermal conditions are changed or reduced to where a corrosion cell can develop. This would be typical of a temporary shutdown, outage, and even a short-term mothballing of the facility. In essence, this is a much shorter time requirement typically represented by a one month to two-month shutdown and possibly a short-term mothballing of up to several months.

A C5 environment and IM-3 (for immersion risk) with medium durability life was selected for evaluating coating performance for this condition.

NOTE For both conditions’ condensation testing was omitted as immersion service was being used.

1. 
   (informative)
   
   Example of test report for CUI coating acceptance

Over all classification requirement - Pass Fail______________

1. 
   (informative)
   
   Example of test report for vertical pipe test

As shown in the diagram below, the test pipe is split into sectors of equal size with 9 levels along the length of the pipe and 4 around the circumference. This gives a total of 36 sectors to be measured. These sectors are labelled with the circumference sector they are in between A and D as well as a number to donate the position along the pipe (1 – 9). The 4 sectors closest to the hotplate are not included as the uncoated bottom edge raises concerns regarding corrosion creep for the uncoated bottom edge. Measure a minimum of 5 DFT measurements for each sector and calculate the mean to record in the table below. An overall mean of each pipe length position is calculated and recorded. Each test pipe shall be evaluated in this way.

NOTE DFT measurements are split into 4 equal-sized quadrants, around the circumference of the pipe. These are denoted as A,B,C and D for each quadrant. The length of the pipe is separated into equal sizes, with length of 50mm, which creates 12 sections, for a total of 48 sections.

Key

A,B,C,D quadrants

C1 section

Figure C.1 — Vertical test pipe

Table C.1 — Pipe length position

Table C.2 — Vertical Pipe Test temperature measurement

Table C.3 — Post-test assessment

Vertical pipe insulation test - Pass Fail _____________ with ________________ Specific brand of insulation

1. 
   (informative)
   
   Optional Cryogenic Cycling Testing
   1. General

Coatings meeting the requirements of the classification CUI-1, CUI-2, and CUI-3 may be tested additionally for acceptance for use in cryogenic cyclic service. Maximum warm temperature shall be as a result of the CUI classification and the “-Cryo” suffix can be added to the original CUI classification to indicate that the coating not only passed the requirements of the CUI classification, but also those of cyclic cryogenic service.

• 1. Cryogenic cycling test

Prepared 316 or 316L stainless steel test panels or as agreed by the parties shall have coating applied, conditioned and heat conditioned in accordance with 6.5.4 and 6.5.5 respectively. Test panels shall be placed in de-ionized water immersion service for 24 hours, then into the cryogenic freezer or bath at −190 °C ± 20 °C for 1 h, and then placed immediately into to water at the maximum of the CUI classification with the hottest water being boiling water at 100 °C for 1 min. This cycle should be repeated 5 times. Table D.1 shows the temperatures and cycles, and Table D.2 provides the acceptance criteria. This test may be performed for other maximum temperature ranges as agreed between the parties.

Table D.1 — Cryogenic cycling test of stainless-steel test panels

Table D.2 — Cryogenic cycling test acceptance criteria

• 1. Adhesion testing after cryogenic cycling test

The artificially aged test panels shall be tested for adhesion after the prescribed duration (time of assessment) in the standard atmosphere in accordance with ISO 554. Table D.3 provides the list of testing and acceptance criteria.

Table D.3 — Adhesion assessment after cryogenic cyclic test

Example of test report for cryogenic cycling test

Optional cryogenic test classification requirement – Pass/Fail________________

Bibliography

[1] ISO 2808, Paints and varnishes — Determination of film thickness

[2] ISO 2812-1, Paints and varnishes — Determination of resistance to liquids — Part 1: Immersion in liquids other than water

[3] ISO 4618, Paints and varnishes — Vocabulary

[4] ISO 4628-1, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 1: General introduction and designation system

[5] ISO 8044, Corrosion of metals and alloys — Vocabulary

[6] ISO 8501-1, Preparation of steel substrates before application of coatings 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

[7] ISO 8501-3, Preparation of steel substrates before application of paints and related products — Visual assessment of surface cleanliness — Part 3: Preparation grades of welds, edges and other areas with surface imperfections

[8] ISO 8503-1, Preparation of steel substrates before application of paints and related products — Surface roughness characteristics of blast-cleaned steel substrates — Part 1: Specifications and definitions for ISO surface profile comparators for the assessment of abrasive blast-cleaned surfaces

[9] ISO 8503-2, Preparation of steel substrates before application of paints and related products — Surface roughness characteristics of blast-cleaned steel substrates — Part 2: Method for the grading of surface profile of abrasive blast-cleaned steel — Comparator procedure

[10] ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests

[11] ISO 12944-1, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 1: General introduction

[12] ISO 12944-2, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 2: Classification of environments

[13] ISO 12944-4, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 4: Types of surface and surface preparation

[14] ISO 12944-5, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 5: Protective paint systems

[15] ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling

[16] NACE SP0198, Control of Corrosion Under Thermal Insulation and Fireproofing Materials — A Systems Approach