NACE HIC steel plates are carbon and low-alloy steel plates manufactured and qualified for resistance to hydrogen induced cracking (HIC) in wet hydrogen sulfide service. These plates are widely used in refineries, gas processing plants, petrochemical units, offshore facilities, and pressure vessel fabrication where sour media can promote internal cracking, stepwise cracking, and sulfide stress related damage.
In industrial procurement, the phrase nace hic steel plates generally refers to plate material supplied with controlled chemistry, clean steelmaking practices, low sulfur content, improved inclusion shape control, and documented testing to project or end-user sour service requirements. Depending on the application, plates may also be ordered with impact testing, normalized or thermomechanically controlled processing, ultrasonic examination, and vessel quality certification.
What Are NACE HIC Steel Plates?
HIC-resistant plates are designed for service in environments containing aqueous H2S, where atomic hydrogen can diffuse into steel and accumulate at inclusions or laminations. If the steel cleanliness and microstructure are not suitable, this can lead to crack initiation and propagation parallel to the rolling surface. For this reason, sour service plate specifications typically require tighter control than standard structural or boiler quality plate.
In practice, buyers often specify these plates for equipment built to ASTM, ASME, or EN pressure vessel standards, while adding supplementary sour service requirements. The plate may be supplied in grades such as pressure vessel quality carbon steel or low-alloy steel, but with additional HIC testing and acceptance criteria defined by the project, fabricator, or end user.
Relevant Standards and Sour Service Requirements
NACE terminology is commonly associated with sour service material selection. While project documents vary, purchasers typically reference recognized standards for corrosion-resistant material qualification in H2S-containing environments. For plate procurement, the most common requirements include:
- HIC testing to demonstrate resistance to hydrogen induced cracking in wet H2S exposure.
- SSC-related considerations where sulfide stress cracking risk exists in welded or stressed components.
- Low sulfur chemistry, often with restricted phosphorus and controlled residual elements.
- Calcium treatment and inclusion control to improve through-thickness performance and reduce crack initiation sites.
- Ultrasonic testing for internal soundness, especially for thicker plates and critical vessel shells.
- Normalized or controlled rolled condition where specified to achieve required toughness and microstructural uniformity.
Depending on the project, procurement documents may call for compliance with pressure vessel standards such as ASTM A516, ASTM A537, or equivalent grades, along with supplementary HIC test reports, heat treatment records, and third-party inspection documentation.
Typical Grades Used for HIC Resistant Plate
The exact plate grade depends on design temperature, pressure, weldability, and code requirements. In many sour service projects, the base material is a standard pressure vessel grade with enhanced sour service qualification. Commonly requested materials include carbon steel vessel plates and selected low-alloy grades used in separators, absorbers, columns, drums, and storage systems.
| Plate Type / Grade | Typical Use | Key Sour Service Features |
|---|---|---|
| ASTM A516 Grade 60/65/70 HIC | Pressure vessels, separators, drums | Low sulfur, HIC tested, good weldability |
| ASTM A537 Class 1 HIC | Higher strength vessel applications | Heat treated plate with sour service qualification |
| EN 10028 pressure vessel grades with HIC testing | Process equipment for international projects | Project-specific chemistry and test acceptance |
| Low-alloy vessel plate for wet H2S duty | Refinery and gas plant equipment | Improved toughness and controlled cleanliness |
For many buyers, grade selection is not only about tensile properties. The more important issue is whether the mill can supply the plate with documented HIC performance, traceable heat numbers, and supplementary testing required by the end user specification.
Chemical and Metallurgical Characteristics
The performance of nace hic steel plates depends heavily on steelmaking quality. Plates intended for wet H2S service are generally produced from fully killed steel with vacuum degassing or equivalent refining routes to reduce harmful elements and improve cleanliness. Lower sulfur levels are especially important because elongated manganese sulfide inclusions can act as crack initiation sites under hydrogen charging conditions.
Typical project requirements may include restricted sulfur, phosphorus, and residual elements, along with calcium treatment for inclusion shape control. Some purchasers also request limits on carbon equivalent to support weldability and heat affected zone performance. For critical pressure equipment, through-thickness properties and ultrasonic soundness may also be specified to reduce the risk of lamellar defects and internal discontinuities.
Although exact chemistry limits differ by mill and project, the objective remains consistent: produce a clean, homogeneous plate with low inclusion content and a microstructure suitable for sour service exposure.
Testing and Acceptance Criteria
Testing is the main differentiator between ordinary vessel plate and HIC-qualified plate. Material is commonly evaluated by laboratory exposure testing in a wet H2S environment, followed by metallographic examination of test specimens. Acceptance is usually expressed through crack-related ratios and project-defined limits.
Common documentation requested by fabricators and EPC contractors includes:
- Mill test certificate with heat number traceability
- Chemical composition and mechanical properties
- Heat treatment condition and plate thickness details
- HIC test report with specimen orientation and acceptance results
- Ultrasonic examination report where required
- Third-party inspection release, if specified
Where service severity is high, the purchaser may also request additional testing after simulated post-weld heat treatment or supplementary notch toughness verification at design temperature. These details should be confirmed before order placement because they affect mill routing, lead time, and plate availability.
Applications in Refinery, Gas, and Process Industries
HIC-resistant steel plates are commonly used in equipment exposed to sour water, amine systems, wet gas, and H2S-containing hydrocarbons. Typical fabricated components include pressure vessel shells, heads, separators, scrubbers, knockout drums, storage vessels, heat exchanger shells, and process columns. In upstream and midstream projects, these plates may also be selected for line pipe accessories, pig traps, and plant equipment where wet H2S conditions are expected.
The need for HIC resistance increases when process conditions allow hydrogen generation and absorption into the steel. For this reason, material selection should be coordinated with corrosion engineering, process data, and applicable code design requirements rather than based on mechanical strength alone.
Procurement Considerations for Buyers
When sourcing nace hic steel plates, buyers should review more than the nominal grade. The purchase order should clearly define the governing material standard, supplementary sour service requirements, plate dimensions, heat treatment condition, and testing protocol. Ambiguous wording can result in supply of standard plate without the enhanced qualification needed for wet H2S service.
Important points to confirm before procurement include plate thickness range, width and length availability, edge condition, quantity by heat, documentation level, and whether the material must be accepted by a third-party inspection agency. If the plate will be used for ASME coded equipment, the order should also align with the fabricator's welding procedure, impact requirements, and any post-weld heat treatment conditions.
For Indian and export projects, traceability and documentation quality are often as important as price. A complete technical review helps avoid delays during fabrication, inspection, and final dossier submission.
Supply Scope and Material Information
HIC-tested plates are generally supplied in a range of thicknesses and dimensions depending on the originating mill and grade. Availability may vary by heat treatment route, vessel quality standard, and project-specific supplementary requirements. Plates can be supplied as full plates, cut sizes, or fabrication-ready blanks, subject to order quantity and inspection needs.
For accurate sourcing, buyers typically provide the following: grade, standard, thickness, width, length, quantity, HIC test requirement, impact test temperature, ultrasonic testing level, certification requirement, and destination. This information allows proper matching of stock or mill production to the intended sour service application.
FAQ
What does HIC mean in steel plates?
HIC stands for hydrogen induced cracking. In wet H2S environments, hydrogen can enter the steel and accumulate at inclusions or internal discontinuities, causing cracks parallel to the plate surface. HIC-resistant plates are produced and tested to reduce this risk.
Are NACE HIC steel plates the same as standard ASTM A516 plates?
No. A standard ASTM A516 plate may meet basic mechanical and chemical requirements, but a NACE HIC plate usually includes additional sour service controls such as lower sulfur, cleaner steelmaking, HIC testing, and project-specific acceptance criteria. The nominal grade can be the same, but the qualification level is different.
Which industries commonly use nace hic steel plates?
These plates are commonly used in oil and gas, refineries, petrochemicals, gas processing, offshore facilities, and other process industries where pressure equipment operates in wet H2S or sour service conditions. Typical applications include separators, drums, columns, and pressure vessels.