Sour Service Stainless Steel Tubes: NACE MR0175 / ISO 15156 Guide
Sour service is an important consideration when stainless steel tubes are used in oil and gas production systems containing hydrogen sulfide (H₂S).
In H₂S-containing environments, metallic materials can be susceptible to hydrogen-related and other forms of environmentally assisted cracking. Depending on the material and service conditions, cracking mechanisms can include sulfide stress cracking (SSC), hydrogen-induced cracking (HIC), stress-oriented hydrogen-induced cracking (SOHIC), stepwise cracking (SWC), and stress corrosion cracking (SCC).
For this reason, oil and gas projects may specify NACE MR0175 / ISO 15156 for materials used in H₂S-containing production environments.
However, NACE MR0175 / ISO 15156 should not be treated simply as a label for a particular stainless steel grade. Material selection and qualification depend on the applicable standard requirements, material condition, manufacturing and processing requirements, and the actual service environment.
For buyers sourcing stainless steel tubes for sour service, it is therefore important to review the complete technical requirement before placing an order.
This guide explains the key considerations for sour service stainless steel tubes, including NACE MR0175 / ISO 15156, material selection, hardness, heat treatment, testing, MTC documentation, and third-party inspection.
What Is Sour Service?
Sour service generally refers to exposure to oilfield environments containing sufficient H₂S to cause cracking of materials by specific mechanisms.
H₂S-containing environments may occur in different oil and gas production applications, including:
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Sour gas production
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Oil and gas wells
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Gas gathering systems
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Production systems
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Injection systems
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Offshore oil and gas facilities
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Subsea production systems
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Natural-gas treatment facilities
The presence of H₂S means that material selection needs to consider potential H₂S-related damage mechanisms.
Depending on the material and environment, these mechanisms may include:
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Sulfide Stress Cracking (SSC)
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Hydrogen-Induced Cracking (HIC)
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Stress-Oriented Hydrogen-Induced Cracking (SOHIC)
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Stepwise Cracking (SWC)
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Stress Corrosion Cracking (SCC)
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Other H₂S-related hydrogen cracking mechanisms
These mechanisms do not affect every material in the same way. Material type, metallurgical condition, manufacturing process, applied or residual stress, and service environment can all affect cracking susceptibility.
Therefore, sour service material selection should be based on the applicable requirements rather than on the presence of H₂S alone.
When Is NACE MR0175 / ISO 15156 Required?
NACE MR0175 / ISO 15156 is intended for materials used in H₂S-containing environments in oil and gas production and related applications within its scope. The standard provides requirements and recommendations for the selection and qualification of metallic materials used in such environments.
The presence of H₂S alone should not be used as a simple rule for selecting a particular stainless steel tube.
A proper review may need to consider factors such as:
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H₂S conditions
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H₂S partial pressure where applicable
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Temperature
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Pressure
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pH
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Chloride concentration
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Water phase
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Material grade
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Material condition
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Heat treatment
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Manufacturing process
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Welding condition, where applicable
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Hardness
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Project specification
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Applicable product standard
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End-user requirements
The applicable requirements should be evaluated together.
This is important because a material listed or commonly used in sour service is not automatically suitable for every H₂S-containing environment. ISO 15156 itself notes that materials covered by the standard are not necessarily immune to cracking under all service conditions.
What Is NACE MR0175 / ISO 15156?
NACE MR0175 / ISO 15156 is a materials standard for H₂S-containing environments in oil and gas production.
The current active designation is ANSI/NACE MR0175-2021 / ISO 15156:2020. The standard covers the selection and qualification of metallic materials for equipment used in H₂S-containing oil and gas production environments.
It supplements, rather than replaces, the material requirements specified by applicable design codes, product standards, regulations, and project specifications.
For stainless steel and other corrosion-resistant alloys, the requirements involve more than simply identifying the alloy grade. Material condition, processing, qualification, and service environment also need to be considered.
ISO 15156-1
ISO 15156-1 establishes general principles for the selection of cracking-resistant materials and addresses material and processing requirements within its scope.
ISO 15156-2
ISO 15156-2 addresses carbon and low-alloy steels and cast irons and includes requirements related to cracking resistance in H₂S-containing production environments.
ISO 15156-3
ISO 15156-3 addresses corrosion-resistant alloys (CRAs) and other alloys and provides requirements related to qualification and verification within the ISO 15156 system.
For stainless steel tubes and nickel alloys, the applicable CRA requirements should therefore be reviewed rather than relying only on the material grade name.
Important: The ISO 15156 series is currently undergoing revision. ISO/DIS 15156 represents a draft fifth edition and should not be treated as the current published edition unless the project specifically requires the applicable draft or revision.
NACE MR0175 vs NACE MR0103
NACE MR0175 / ISO 15156 and NACE MR0103 / ISO 17945 address different application areas.
| Item | NACE MR0175 / ISO 15156 | NACE MR0103 / ISO 17945 |
|---|---|---|
| Primary application | Oil and gas production | Petroleum refining and related processing |
| Environment | H₂S-containing production environments | Sour petroleum refining environments |
| Main material concern | H₂S-related cracking resistance | Sulfide stress cracking resistance |
| Typical users | Oil and gas producers, equipment manufacturers, contractors | Refiners, equipment manufacturers, engineering and construction contractors |
| Selection basis | Applicable production environment and material requirements | Applicable refining environment and material requirements |
NACE MR0175 / ISO 15156 is intended for oil and gas production environments within its scope. NACE MR0103 / ISO 17945 addresses sour petroleum refining and related processing environments.
Therefore, buyers should confirm which standard is specified by the project rather than automatically applying MR0175 to every sour application.
Why Stainless Steel Tubes Need Sour Service Review
Stainless steel is widely used where corrosion resistance is required, but corrosion resistance under normal conditions does not automatically mean that a particular stainless steel tube is suitable for every sour service application.
For a sour service tube order, the following information may need to be reviewed:
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Material grade
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Product standard
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Material condition
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Heat treatment
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Hardness
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H₂S conditions
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Temperature
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Pressure
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pH
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Chloride concentration
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Manufacturing process
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Welding condition, where applicable
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Testing requirements
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Inspection requirements
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Documentation requirements
The material should be evaluated against the actual service conditions and the applicable project requirements.
This approach is more reliable than asking a supplier only for a "NACE material."
What Factors Affect Sour Service Material Selection?
H₂S Conditions
H₂S is a fundamental consideration in sour service. Depending on the applicable requirements, the H₂S conditions and other environmental parameters can affect material selection and the limits within which a material may be used.
Temperature
Temperature can affect the susceptibility of materials to environmentally assisted cracking and therefore needs to be considered when evaluating material suitability.
pH
pH is an important environmental parameter in sour service material selection. Applicable material requirements may define environmental limits involving pH.
Chloride
Chloride can be particularly important when evaluating corrosion-resistant alloys because chloride-containing environments can influence corrosion and cracking susceptibility.
Pressure
Pressure and H₂S partial pressure may be relevant to the assessment of sour service conditions.
Material Condition
The same nominal alloy grade can have different material conditions depending on manufacturing and heat treatment.
Therefore, the material grade alone is not enough to establish suitability.
Hardness
Hardness is an important material property in sour service assessment, particularly because cracking susceptibility can be affected by material condition and hardness.
For this reason, project requirements may specify hardness control or hardness testing for applicable materials.
The actual acceptance criteria should always be taken from the applicable standard and project specification rather than from a generic value.
Stainless Steel and Nickel Alloys for Sour Service
Different stainless steels, duplex stainless steels, super duplex stainless steels, and nickel alloys may be considered for oil and gas applications.
However, a material should not be selected solely because it has a higher alloy content or because it is commonly used in corrosive environments.
The applicable sour service requirements must be checked for the specific material and service conditions.
316L Stainless Steel
316L is a widely used austenitic stainless steel. It may be considered for applications where its corrosion resistance and other properties meet the project requirements.
For sour service, suitability should be evaluated against the applicable ISO 15156 requirements and the actual service environment.
317L Stainless Steel
317L contains higher molybdenum than 316L and may be selected where additional corrosion resistance is required.
Its suitability for a particular sour service application still needs to be evaluated against the applicable requirements.
Duplex 2205
Duplex stainless steel 2205 combines austenitic and ferritic microstructural characteristics and is commonly considered when both corrosion resistance and mechanical performance are important.
For sour service applications, material condition, heat treatment, hardness, and manufacturing requirements should be reviewed.
Super Duplex 2507
Super duplex stainless steels may be considered for applications requiring high corrosion resistance and mechanical performance.
As with other alloys, the specific service environment and applicable sour service requirements must be confirmed before selection.
Nickel Alloys
Nickel-based alloys such as Alloy 825, Alloy 625, and Alloy C276 may be considered for demanding corrosion environments.
However, these alloys should not be presented as universally suitable for sour service. The applicable ISO 15156 requirements, environmental conditions, material condition, and project specification must be reviewed for the specific application.
Material selection principle: A stainless steel or nickel alloy grade should not be described as universally "NACE compliant." Suitability depends on the applicable standard requirements and the specified service conditions.
SSC vs HIC: What Is the Difference?
H₂S-containing environments can cause different types of cracking, and these mechanisms should not be treated as interchangeable.
Sulfide Stress Cracking (SSC)
SSC is a form of hydrogen-related cracking associated with H₂S-containing environments and susceptible materials under tensile stress.
Material strength, hardness, metallurgical condition, environmental conditions, and stress can all be relevant to susceptibility.
Hydrogen-Induced Cracking (HIC)
HIC involves hydrogen entering susceptible metallic materials and contributing to internal cracking.
ISO 15156-2 specifically addresses HIC and its possible development into stepwise cracking for the carbon and low-alloy steels within its scope.
Stepwise Cracking (SWC)
Stepwise cracking describes the linking of hydrogen-induced cracks on adjacent planes within a steel.
HIC and SWC should therefore not simply be treated as two unrelated forms of cracking.
Stress Corrosion Cracking (SCC)
SCC involves cracking associated with corrosion processes and tensile stress. In H₂S-containing environments, the susceptibility depends on the material and environmental conditions.
The applicable standard should be used to determine which cracking mechanisms and requirements are relevant to the material and application.
Sour Service Testing for Stainless Steel Tubes
Testing requirements should be determined from the applicable product standard, NACE/ISO requirements, project specification, and purchaser requirements.
Not every test is automatically required for every stainless steel tube order.
Hardness Testing
Hardness testing may be specified to verify that the material meets the applicable requirements.
Where hardness limits apply, the test results should be documented and traceable to the supplied material.
PMI Testing
Positive Material Identification (PMI) can be used to verify the alloy identity of supplied material.
PMI requirements should be confirmed in the purchase specification.
Hydrostatic Testing
Hydrostatic testing may be required by the applicable tube/product specification or project requirement.
The test requirement and acceptance criteria should be agreed before production.
Eddy Current Testing
Eddy current testing may be specified as a non-destructive examination method for applicable tube products.
Whether it is required depends on the product standard and purchase specification.
Ultrasonic Testing
Ultrasonic testing may be required for specific tube products or project requirements.
The applicable standard should define the scope and acceptance requirements where applicable.
HIC Testing
HIC testing should not be added automatically to every stainless steel sour service tube order.
The need for HIC testing should be confirmed according to the material, applicable standard, project specification, and purchaser requirement.
SSC Testing
Similarly, SSC testing should be specified where required by the applicable material qualification or project requirements.
The testing method and acceptance criteria should be agreed before production.
Manufacturing and Heat Treatment Considerations
For sour service applications, the manufacturing condition of the tube can be as important as the nominal material grade.
Buyers should clarify:
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Seamless or welded construction
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Heat treatment condition
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Solution annealing where applicable
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Cold working condition where applicable
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Hardness requirements
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Welding condition
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Non-destructive examination
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Surface requirements
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Traceability
For welded tubes, the weld and heat-affected zone may require particular attention because the manufacturing process can affect the metallurgical condition of the material.
Therefore, the purchase specification should clearly define the required manufacturing and heat treatment condition before production begins.
NACE Compliance vs Product Standards
NACE MR0175 / ISO 15156 should not be treated as a replacement for the product standard.
A stainless steel tube order may involve several layers of requirements, for example:
Product specification
→ Defines the requirements for the tube product
Material grade
→ Defines the specified alloy
Sour service requirement
→ Defines the applicable H₂S-related material requirements
Inspection and testing
→ Defines the required verification
Documentation
→ Defines the certificates and records required for delivery
This distinction is important when preparing a purchase inquiry.
Instead of simply writing:
NACE stainless steel tube
a buyer should provide as much of the following information as possible:
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Material grade
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Product standard
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Tube dimensions
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Seamless or welded requirement
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Sour service requirement
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Applicable NACE / ISO standard
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Service conditions
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Heat treatment requirement
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Hardness requirement
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Testing requirement
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Inspection requirement
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MTC requirement
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Third-party inspection requirement
This gives the supplier enough information to review the inquiry properly.
What Should Be Included in the MTC?
For sour service tube orders, the Mill Test Certificate (MTC) should be reviewed carefully.
Depending on the applicable product standard and purchase specification, the documentation may include:
Material Identification
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Material grade
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Heat number
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Product identification
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Tube size
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Quantity
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Product standard
Chemical Composition
The certificate should provide the required chemical composition information according to the applicable material/product standard.
Mechanical Properties
Depending on the applicable specification, this may include:
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Tensile properties
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Yield strength
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Elongation
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Hardness
Heat Treatment
The applicable heat treatment condition and relevant records should be confirmed where required.
Testing and Inspection
The MTC and inspection documentation may include applicable test results, such as:
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Hydrostatic testing
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Non-destructive examination
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PMI
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Hardness testing
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Other project-specified testing
Certificate Type
The buyer should confirm whether EN 10204 3.1 or 3.2 documentation is required.
Where third-party inspection is required, this should also be agreed before production.
Buyer Checklist for Sour Service Stainless Steel Tubes
Before placing an order, buyers should prepare a clear technical inquiry.
Product Information
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Material grade
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Product standard
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Outside diameter
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Wall thickness
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Length
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Quantity
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Seamless or welded requirement
Sour Service Information
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Sour service requirement
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Applicable NACE / ISO standard
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H₂S information
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H₂S partial pressure, where available
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pH
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Chloride concentration
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Working temperature
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Working pressure
Manufacturing Requirements
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Heat treatment
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Material condition
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Hardness requirement
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Welding requirements, where applicable
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Surface requirements
Testing Requirements
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Hydrostatic test
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PMI
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Eddy current testing
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Ultrasonic testing
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HIC testing, if specified
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SSC testing, if specified
Documentation and Inspection
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MTC
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EN 10204 3.1 or 3.2
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Heat number traceability
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Third-party inspection
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Project-specific inspection documentation
Delivery Information
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Destination country or port
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Required delivery schedule
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Packing and marking requirements
A clear inquiry allows the supplier to review the technical requirements before quotation and helps reduce the risk of material, testing, or documentation issues later in the order.
Example: Sour Gas Injection Line
Consider a sour gas injection line where stainless steel or nickel alloy tubes are being considered.
Before production, the buyer and supplier may need to confirm:
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Applicable NACE MR0175 / ISO 15156 requirements
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Material grade
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Product standard
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Sour service conditions
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Material condition
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Heat treatment
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Hardness requirements
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PMI requirements
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Hydrostatic testing
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Applicable NDE requirements
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HIC or SSC testing, if specified
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MTC requirements
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EN 10204 3.1 or 3.2 requirements
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Third-party inspection requirements
The exact testing and inspection scope should be established before production.
This is particularly important when special testing or third-party inspection is required because late changes to the inspection plan can affect production scheduling and delivery.
Sour Service Tube Supply and Inspection Support from DLSS
DLSS supplies stainless steel, duplex, super duplex, and nickel alloy tubes for oil and gas, refinery, offshore, and chemical projects.
For sour service tube projects, DLSS can support buyers with technical requirement review and quality documentation.
The available support includes:
Material and Requirement Review
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Material grade review
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Sour service requirement review
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NACE requirement review
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Service condition review
Quality Control and Testing
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MTC review
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Heat number traceability
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Hardness testing
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PMI testing
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Hydrostatic testing
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Eddy current testing
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Ultrasonic testing
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HIC test coordination, where required
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SSC test coordination, where required
Documentation and Inspection
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EN 10204 3.1 documentation
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EN 10204 3.2 inspection support
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Third-party inspection support
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Project documentation review
Where required by the project, DLSS can coordinate with project-approved third-party inspection companies, including BV, SGS, TÜV, LR, ABS, DNV, or other approved inspection organizations.
The exact inspection scope should be confirmed according to the project specification and purchase order.
Common Mistakes to Avoid When Ordering Sour Service Tubes
1. Asking Only for "NACE Material"
"NACE material" is not sufficient technical information for a sour service tube order.
The material and service requirements need to be evaluated together.
2. Ignoring the Service Environment
H₂S conditions, temperature, pressure, pH, chloride concentration, and other relevant parameters may affect material selection.
3. Choosing a Material Only by Grade
A material grade alone does not establish suitability for every sour environment.
Material condition and applicable requirements must also be considered.
4. Confusing MR0175 with MR0103
MR0175 / ISO 15156 is associated with oil and gas production environments within its scope, while MR0103 / ISO 17945 addresses sour petroleum refining and related processing environments.
5. Ignoring Hardness and Heat Treatment
Material condition and processing can be important to sour service performance.
6. Adding Special Testing Too Late
If HIC, SSC, PMI, third-party inspection, or other special requirements are needed, they should be confirmed before production.
7. Not Checking the MTC
Material grade, heat number, chemical composition, mechanical properties, heat treatment, and required testing documentation should be reviewed against the purchase specification.
8. Treating All Stainless Steel Grades as Equivalent
Different stainless steels, duplex grades, super duplex grades, and nickel alloys have different properties and different requirements for specific applications.
FAQ About Sour Service Stainless Steel Tubes
Is 316L stainless steel suitable for sour service?
316L may be considered for some applications, but it should not be described as universally suitable for sour service. Suitability depends on the applicable NACE MR0175 / ISO 15156 requirements, material condition, and actual service environment.
Does all H₂S-containing service require NACE MR0175?
Not automatically. The applicability of NACE MR0175 / ISO 15156 depends on the application and the scope of the standard. The project specification and service conditions should be reviewed before selecting materials.
What is the difference between NACE MR0175 and MR0103?
NACE MR0175 / ISO 15156 addresses materials for H₂S-containing oil and gas production environments within its scope. NACE MR0103 / ISO 17945 addresses sour petroleum refining and related processing environments.
What information should I provide when requesting sour service stainless steel tubes?
At minimum, provide the material grade, product standard, tube dimensions, quantity, sour service requirement, available H₂S and environmental information, heat treatment requirements, testing requirements, MTC requirements, and inspection requirements.
Is HIC testing required for stainless steel sour service tubes?
Not automatically. HIC testing requirements depend on the material, applicable standard, project specification, and purchaser requirements.
Is SSC testing required for every NACE tube?
No. The required testing should be determined from the applicable standard, material requirements, and project specification.
What documents should be supplied with sour service tubes?
Depending on the order, documentation may include the MTC, heat number traceability, test results, inspection records, EN 10204 3.1 or 3.2 documentation, and third-party inspection records where required.
Can welded stainless steel tubes be used in sour service?
The suitability of welded tubes depends on the material, manufacturing condition, welding requirements, service environment, applicable standard, and project specification. The weld and heat-affected zone may require specific consideration.
What is the difference between HIC and SSC?
HIC involves hydrogen-related internal cracking in susceptible materials, while SSC is associated with hydrogen-related cracking under tensile stress in H₂S-containing environments. The applicable material and service conditions determine which mechanisms and requirements need to be considered.
Can DLSS support third-party inspection?
DLSS can support third-party inspection requirements for sour service tube projects. The inspection organization and scope should be confirmed according to the project specification and purchase order.
Conclusion
Sour service stainless steel tube selection is not simply a matter of choosing a stainless steel grade and asking for "NACE compliance."
For H₂S-containing oil and gas production environments, NACE MR0175 / ISO 15156 provides requirements and recommendations for the selection and qualification of metallic materials within its scope. Material grade, material condition, processing, service environment, and applicable testing and documentation requirements all need to be considered.
For buyers, the most important step is to provide complete technical information before ordering.
This includes:
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Material grade
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Product standard
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Tube dimensions
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Sour service conditions
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H₂S information
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Temperature and pressure
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pH and chloride information where relevant
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Heat treatment
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Hardness
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Testing
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MTC requirements
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Inspection requirements
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Third-party inspection requirements
NACE MR0175 / ISO 15156 should also be distinguished from NACE MR0103 / ISO 17945, which addresses sour petroleum refining and related processing environments.
DLSS supports stainless steel, duplex, super duplex, and nickel alloy tube projects with material review, MTC review, hardness testing, PMI, hydrostatic testing, applicable NDE, HIC / SSC test coordination, EN 10204 3.1 / 3.2 documentation, third-party inspection support, and export packing.
If you are sourcing stainless steel, duplex, super duplex, or nickel alloy tubes for sour service, send DLSS your material grade, product standard, tube dimensions, quantity, service conditions, and inspection requirements. The technical requirements can then be reviewed before quotation.