Sour service environments destroy ordinary steel from the inside out. Hydrogen atoms released by hydrogen sulfide (H₂S) work their way into the plate structure and split it apart along internal planes, long before any visible corrosion shows up on the surface. That single fact separates HIC Plates from Non-HIC Plates and decides which one belongs in a sour gas pipeline versus a standard structural frame. Choosing the wrong grade risks cracked vessels, unplanned shutdowns, and safety incidents. This blog compares HIC-tested and non-HIC plates so buyers can match material to the operating environment with confidence.
What are HIC Plates and Non-HIC Plates?
HIC Plates undergo hydrogen-induced cracking resistance testing under NACE TM0284, where samples soak in an acidified H₂S solution for 96 hours and get checked for internal cracking. Non-HIC Plates skip this test entirely and rely on standard mechanical and chemical checks like tensile strength, yield strength, and impact toughness. HIC testing confirms the steel’s cleanliness and inclusion content control blister formation and crack propagation caused by absorbed hydrogen. Without it, a plate that passes every conventional quality check can still fail catastrophically in a sour environment within months of installation.
Types of HIC Plates
HIC-tested plates come in multiple grades matched to pressure, thickness, and sourness levels. ASTM A516 GR 70 (NACE + HIC) Plate suits higher-pressure vessels needing both strength and hydrogen resistance, while the ASTM A516 GR 60 HIC Plate covers moderate-pressure applications where slightly lower tensile requirements still demand full sour-service protection. Other common specifications include A516 GR 65 and API 5L PSL2 pipe-grade plates with HIC certification. Grade selection depends on design pressure, H₂S partial pressure in the process stream, and the fabrication code the project follows.
HIC Tested vs Non-HIC Plates: Key Differences
Resistance to Hydrogen-Induced Cracking
HIC plates resist hydrogen damage through controlled sulfur content, low inclusion levels, and calcium treatment during steelmaking, which stops hydrogen atoms from collecting at inclusion boundaries and forming blisters. Non-HIC plates carry no such guarantee. In H₂S service, they crack internally within a short operating window. Over a 15 to 20 year vessel life, that difference determines whether equipment survives or fails early.
Manufacturing and Testing Requirements
HIC testing follows NACE TM0284 procedures, exposing three sample sections per plate to an acidified solution and measuring crack length ratio, crack thickness ratio, and crack sensitivity ratio against strict pass thresholds. Full NACE MR0175 compliance covers hardness limits and material traceability too. Non-HIC plates only go through standard mill testing, tensile, bend, and impact tests, with no exposure to simulated sour conditions at all.
Mechanical Properties
Both plate types can share identical tensile and yield strength ranges within a grade, since HIC testing adds a hydrogen-resistance requirement rather than changing base strength. The real difference shows up in toughness consistency and crack resistance under cyclic loading. HIC plates hold structural integrity in corrosive, high-stress service where Non-HIC plates would develop internal defects first.
Corrosion Resistance in Sour Service
In environments containing H₂S, moisture, and CO₂, Non-HIC plates absorb hydrogen and blister within weeks of exposure. HIC plates resist this through their controlled microstructure and pass 96-hour NACE exposure testing before certification. That resistance protects pressure vessels, separators, and pipelines from sudden leaks. Equipment safety in refineries and gas plants depends directly on this margin.
Typical Industrial Applications
Oil and gas production, sour gas processing, refineries, and offshore platforms all specify HIC plates for vessels and piping exposed to H₂S. Non-HIC plates suit structural steel, storage tanks handling non-corrosive fluids, and general fabrication where sour gas exposure never occurs. Operating pressure, H₂S concentration, and moisture content in the process stream ultimately decide which material a project needs.
Cost vs Long-Term Performance
HIC plates cost 15 to 25% more per ton than standard non-HIC grades due to tighter steelmaking control and mandatory testing. That upfront premium offsets against avoided vessel replacement, unplanned shutdowns, and inspection failures over a 20-year service life. In sour environments, the lifecycle cost of Non-HIC material almost always exceeds the initial savings.
Quick Comparison Table
| Parameter | HIC Plates | Non-HIC Plates |
| HIC resistance | Confirmed via NACE TM0284 | Not tested |
| Testing requirements | 96-hour sour exposure test | Standard mill tests only |
| Sour service suitability | Suitable | Not suitable |
| Mechanical performance | Stable under cyclic sour stress | Degrades in H₂S service |
| Common applications | Sour gas, refinery vessels | Structural, non-sour tanks |
| Overall durability | 15-20+ years in sour service | Short service life in H₂S |
When Should You Choose HIC Plates?
Sour gas processing plants handling H₂S-laden streams need HIC plates without exception, as do pressure vessels storing or processing sour crude and gas. This grade is a default requirement for oil and gas production facilities, refineries and petrochemical plants operating to NACE MR0175 project specifications. Where the client’s engineering standard requires NACE compliance, any application automatically excludes non-HIC material. Choose HIC-tested plates whenever the design documents reference H₂S partial pressure limits or sour service classification, since substituting standard steel at that stage creates a compliance failure as well as a safety risk.
Common Mistakes to Avoid When Selecting HIC Plates
Buyers often assume every carbon steel plate qualifies as HIC tested simply because it meets the same ASTM grade designation. This is wrong because HIC certification is a separate additional test. If you ignore NACE MR0175 compliance requirements during procurement, you are going to have material rejected at inspection. If you skip reviewing the mill test certificates, you will not have the crack length ratio and crack sensitivity ratio data to confirm actual pass results. If you select material based on price alone, without checking the sour service exposure levels, you are inviting premature failure. The most common and most expensive selection mistake is not to consider the actual service conditions, including the H₂S concentration and the presence of moisture.
Conclusion
HIC Plates and Non-HIC Plates differ in testing rigor, hydrogen resistance, and suitability for sour service. HIC-tested material undergoes NACE TM0284 exposure testing that Non-HIC plates never see, making it the only reliable choice for H₂S-containing environments. Selecting the correct plate type protects equipment safety, reduces unplanned downtime, and extends service life in demanding industrial conditions.
RPF Pipes & Fittings stocks both HIC and non-HIC grades across multiple thicknesses and sizes, ready for dispatch from Vadodara. Visit us at RPF Pipes & Fittings to check stock availability and request a quote for your project’s exact grade and specification.