A516 NACE HIC is a common procurement term for ASTM A516 pressure vessel quality carbon steel plate ordered with additional sour service and hydrogen induced cracking (HIC) resistance requirements. In most cases, buyers are referring to ASTM A516 Grade 60, Grade 65, or Grade 70, with Grade 70 being the most frequently specified for refinery, gas processing, separator, amine unit, and pressure vessel fabrication work.
The key technical point is that ASTM A516 alone does not automatically mean NACE-compliant or HIC-tested. The base ASTM specification defines chemical composition, tensile properties, and general delivery requirements. Suitability for wet H2S environments is normally achieved only when the purchase order, project specification, or end-user standard adds the required controls for steel cleanliness, sulfur, hardness, ultrasonic examination, heat treatment condition, and laboratory testing.
What A516 NACE HIC Means in Practice
The phrase a516 nace hic compresses three separate requirement groups into one commercial shorthand:
- ASTM A516 – carbon steel plate for pressure vessel service, especially at moderate and lower temperatures.
- NACE sour service requirements – usually linked to material selection for wet H2S service under NACE MR0175 / ISO 15156, NACE MR0103, or owner-specific refinery and gas plant material specifications.
- HIC resistance – demonstrated by laboratory testing, commonly to NACE TM0284, with acceptance criteria based on CLR (crack length ratio), CTR (crack thickness ratio), and CSR (crack sensitivity ratio).
Because market usage is inconsistent, technical review is essential. A plate described only as A516 HIC or A516 NACE should be checked against the exact project requirement for test solution, exposure duration, sample orientation, hardness limit, impact testing, heat treatment condition, and documentation package.
Typical ASTM A516 Grades Used for Sour Service
The most common grades are ASTM A516 Gr 60, ASTM A516 Gr 65, and ASTM A516 Gr 70. Among these, A516 Gr 70 NACE HIC is the most widely requested because it offers a practical balance of strength, weldability, fabrication familiarity, and broad mill availability.
For HIC-resistant plate, mills generally apply cleaner steelmaking practices than those required by the base ASTM standard. These may include low sulfur melting, calcium treatment or inclusion shape control, vacuum degassing, segregation control, and tighter internal quality limits. Depending on thickness and project specification, the plate may be supplied as-rolled or normalized, with normalized condition often preferred where improved toughness consistency and more uniform microstructure are required.
Relevant Standards for A516 NACE HIC Plate
There is no single standalone material specification called “A516 NACE HIC.” Compliance is created by combining the base plate standard with supplementary sour service requirements and test references. The standards most often reviewed during procurement are listed below.
| Reference | Scope | Why it matters for A516 NACE HIC |
|---|---|---|
| ASTM A516 / ASME SA516 | Pressure vessel quality carbon steel plate | Defines grade, chemistry, tensile properties, and base supply requirements |
| NACE MR0175 / ISO 15156 | Materials for H2S-containing environments in oil and gas production | Used as the principal sour service selection framework |
| NACE MR0103 | Materials resistant to sulfide stress cracking in corrosive petroleum refining environments | Frequently referenced in refinery and downstream applications |
| NACE TM0284 | Evaluation of pipeline and pressure vessel steels for resistance to HIC | Defines HIC test methodology and reporting of CLR, CTR, and CSR |
| ASTM A578 / A578M | Ultrasonic examination of steel plates | Used to specify internal soundness and UT acceptance level |
| Project or end-user specification | Additional purchaser requirements | Usually sets hardness limits, sulfur maximum, impact testing, and documentation |
Typical Technical Requirements Buyers Should Verify
When sourcing A516 NACE HIC plate, the most important issue is not the sales description but the exact technical schedule attached to the order. Requirements vary by refinery, EPC contractor, and vessel design code, but the following checkpoints are commonly reviewed:
- Grade and thickness range – A516 Gr 60, 65, or 70 with required plate dimensions.
- Supply condition – as-rolled, normalized, or normalized plus supplementary testing.
- Sulfur restriction – often tighter than base ASTM, commonly low-S heats for improved HIC resistance.
- Hardness limit – purchaser-defined maximum hardness to reduce sour service cracking risk.
- HIC test requirement – NACE TM0284 solution, duration, sample location, and acceptance criteria.
- Ultrasonic testing – ASTM A578 level or project-specific internal quality requirement.
- Impact testing – if vessel design temperature or project specification requires notch toughness verification.
- Heat treatment and traceability – full traceability by heat number and mill test certification.
- Third-party inspection – if witness, review, stamping, or release by an inspection agency is required.
In practical procurement, many rejections occur because the order states only “A516 NACE HIC” without defining the actual acceptance criteria. For engineering control, the purchase order should state the exact standard edition, supplementary requirements, and test report expectations.
HIC Testing and Acceptance Criteria
HIC resistance is typically demonstrated by testing in accordance with NACE TM0284. Test coupons are exposed to a defined sour environment, after which the specimen is sectioned and examined for internal cracking. Results are commonly reported using:
- CLR – Crack Length Ratio
- CTR – Crack Thickness Ratio
- CSR – Crack Sensitivity Ratio
The acceptance values are not universal. Different end users specify different maximum limits, and some projects also require through-thickness testing, metallographic review, or SSC-related restrictions. This is why a statement such as “HIC tested plate” is incomplete unless the report identifies the test solution, specimen orientation, duration, and actual acceptance criteria achieved.
For many pressure vessel applications, buyers also request low inclusion content, controlled centerline segregation, and improved plate cleanliness because HIC performance is strongly influenced by steelmaking quality rather than tensile strength alone.
Manufacturing Features That Support Sour Service Performance
Although the final requirement is verified by testing, certain manufacturing controls are commonly associated with reliable A516 NACE HIC plate supply:
- Low sulfur steelmaking to reduce elongated sulfide inclusions
- Calcium treatment for inclusion modification
- Vacuum degassing for cleaner steel and hydrogen control
- Controlled rolling or normalizing for microstructural consistency
- Improved internal soundness confirmed by ultrasonic examination
- Heat-by-heat traceability and complete mill documentation
These controls do not replace HIC testing, but they are often part of the manufacturing route used for plates intended for wet H2S service in separators, columns, drums, and pressure-retaining equipment.
Procurement Guidance for ASTM A516 Gr 70 NACE HIC
For many projects, ASTM A516 Grade 70 NACE HIC is the default selection because of its established use in fabricated vessels. However, the material should be ordered by full technical description rather than by keyword alone. A robust line item may include the base standard, grade, supply condition, HIC test method, acceptance limits, UT class, hardness requirement, and any impact or supplementary tests required by the design basis.
Example procurement wording may include the following elements: ASME SA516 Gr 70 plate, normalized, HIC tested to NACE TM0284, acceptance criteria as per project specification, low sulfur, hardness controlled, UT tested to ASTM A578, with complete MTC and traceability. The exact wording should always be aligned with the end-user material requisition and approved vendor list.
From an engineering standpoint, the term a516 nace hic should therefore be treated as a starting point for specification review, not as a complete material definition. The decisive factors are the referenced standards, the mill route, and the documented test results supplied with the plate.
FAQ
Is A516 NACE HIC a separate ASTM grade?
No. It is not a standalone ASTM designation. It usually means ASTM A516 plate ordered with additional sour service and HIC testing requirements defined by NACE standards and project specifications.
Which grade is most common for A516 NACE HIC plate?
ASTM A516 Grade 70 is the most commonly specified grade, followed by Grade 60 and Grade 65. Grade selection depends on design strength, thickness, fabrication requirements, and project approval.
Does ASTM A516 automatically comply with NACE MR0175 or TM0284?
No. Standard ASTM A516 plate does not automatically meet NACE sour service or HIC test requirements. Compliance must be specifically ordered, tested, and documented in accordance with the applicable project and end-user specification.