H.I.C. Testing

HIC is a form of hydrogen damage in which atomic hydrogen — generated by the corrosion of steel in wet H₂S environments — diffuses into the steel and accumulates at internal defects such as non-metallic inclusions and segregation bands. The localised buildup of hydrogen pressure initiates and propagates planar cracks oriented parallel to the rolling direction of the steel, without the need for any external applied stress.

After 96 hours of immersion in H₂S-saturated solution, each specimen is sectioned, polished, and examined metallographically. All cracks found on the cross-sections are measured and used to calculate three parameters: CLR (Crack Length Ratio), CTR (Crack Thickness Ratio), and CSR (Crack Sensitivity Ratio). These quantify the extent of cracking relative to the specimen dimensions.

NACE TM0284 itself does not define universal acceptance criteria — it defines the test method only. Acceptance limits are specified by the applicable material standard, project specification, or by mutual agreement between supplier and purchaser. Common limits referenced in industry specifications include CLR < 15%, CTR < 5%, CSR < 2%, but these may vary. SMT reports all three parameters and the raw crack measurements, allowing the client to apply any acceptance criteria required.

Solution A is an acidified brine (5% NaCl + 0.5% CH₃COOH) saturated with H₂S, simulating sour production environments in oil and gas wells. Solution B is synthetic seawater (per ASTM D1141) saturated with H₂S, intended for applications involving offshore or marine environments. The two solutions produce different corrosion conditions and can yield different HIC severity on the same steel. Both are included in SMT's accredited scope.

Following the most recent revision of ANSI/NACE TM0284, the applicable product forms include: seamless and welded pipes (base metal and weld area), plates, fittings, and flanges. SMT machines specimens from all these product forms in its in-house workshop, including the specific orientations (L-T, S-L, S-T) required by the standard.

NACE TM0284 requires a minimum of three specimens per test condition (i.e., per solution). For pipes, both base metal and weld area specimens are typically required. For full qualification of a product, it is common to test three specimens in Solution A and three in Solution B, for a total of six specimens per product/heat. SMT can advise on the sampling plan based on the applicable material standard or project specification.

Yes. SMT's in-house mechanical workshop machines HIC specimens directly from pipe sections, plates, or cut material supplied by the client, to the exact dimensions and surface finish required by NACE TM0284. This includes control of specimen orientation relative to the rolling direction, which is critical for meaningful results. Full dimensional records are maintained.

HIC (Hydrogen Induced Cracking) occurs under no external applied stress. Cracking is driven entirely by internal hydrogen pressure at microstructural defects and propagates parallel to the rolling direction. SSC (Sulphide Stress Cracking) requires the simultaneous presence of H₂S, tensile stress (residual or applied), and a susceptible microstructure. SSC cracks are typically perpendicular to the applied stress direction. Both mechanisms involve hydrogen from H₂S corrosion but differ fundamentally in their driving force and morphology. SMT performs both HIC and SSC testing.

The immersion phase alone is 96 hours (4 days) per NACE TM0284. Added to this are specimen preparation time before testing and metallographic examination, measurement, and report preparation afterward. From receipt of specimens, a typical turnaround is 10–15 working days for the complete accredited test report. Rush scheduling can be discussed for urgent requirements. Contact us for current availability.

Yes, significantly. HIC susceptibility is strongly influenced by the type, size, and distribution of non-metallic inclusions — particularly elongated MnS inclusions and centreline segregation in continuously cast steels. Low-sulphur steels (< 0.002% S) with inclusion shape control (calcium or rare earth treatment) generally perform better in HIC testing. The test is therefore sensitive to both the steelmaking route and the rolling conditions.

Yes. SMT holds ACCREDIA accreditation No. 00588 under UNI CEI EN ISO/IEC 17025:2018. ACCREDIA is a signatory to the EA (European co-operation for Accreditation) multilateral agreement (MLA), which means accredited test reports from SMT are recognised across Europe and, through ILAC mutual recognition arrangements, worldwide. This is particularly relevant for oil and gas qualification projects involving international operators, EPCs, or certification bodies.

Yes. SMT offers a full corrosion testing programme that covers all the main damage mechanisms relevant to sour service and other corrosive environments, including SSC (NACE TM0177), pitting and crevice (ASTM G48), intergranular corrosion (ASTM A262, ASTM G28, ISO 3651), and CSCC (ASTM G36). Combined qualification programmes can be managed by a single Job Manager, reducing coordination overhead and lead time.