Stainless Steel Coil Tube — NACE TM0284 Hydrogen-Induced Cracking (HIC) Certified
Product Overview
The Stainless Steel Coil Tube is a precision-engineered tubular product designed for demanding sour service environments where exposure to hydrogen sulfide (H2S) gas poses significant corrosion and cracking risks. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube undergoes rigorous Hydrogen-Induced Cracking (HIC) testing in strict accordance with the internationally recognized NACE TM0284 standard. The product is classified as a mandatory inspection item for sour-resistant piping systems compliant with NACE MR0175 (ISO 15156), ensuring long-term structural integrity in aggressive downhole and surface processing applications.
Material & Properties
The coil tube is fabricated from austenitic and duplex stainless steel grades specifically selected for their superior resistance to sulfide stress cracking (SSC) and hydrogen-induced cracking. Key material characteristics include:
- Corrosion Resistance: Exceptional resistance to uniform and localized corrosion in H2S-saturated environments, including wet H2S, acid gas, and sour water.
- Mechanical Integrity: Maintains full tensile and yield strength after prolonged exposure to corrosive media, with no measurable loss of ductility or fracture toughness.
- Hydrogen Resistance: Demonstrates zero cracking initiation and propagation under NACE TM0284 test conditions, confirming immunity to hydrogen embrittlement mechanisms.
- Temperature Range: Suitable for continuous service from cryogenic temperatures up to 260°C (500°F) in sour service applications.
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) |
| Material Grades | Austenitic SS (304, 316, 321) / Duplex SS (2205, 2507) |
| Applicable Standards | NACE MR0175 / ISO 15156; NACE TM0284 |
| HIC Test Standard | NACE TM0284 — Determination of Resistance of Metals to Hydrogen-Induced Cracking |
| Test Solution | H2S-saturated 3.5% NaCl solution (Amine-impregnated) |
| Test Duration | 96 hours (continuous immersion) |
| Test Temperature | 23°C ± 2°C (73°F ± 4°F) |
| Acid Number (AN) | 2.0 mL KOH/g (minimum) |
| Acceptance Criteria | No HIC cracking (Crack Index = 0) |
| Coil Outer Diameter | Customizable (typical range: 600 mm – 2,500 mm) |
| Tube Wall Thickness | 0.5 mm – 6.0 mm (custom per order) |
| Surface Finish | 2B / No. 4 / Electropolished (EP) |
Manufacturing Process
The production of HIC-certified stainless steel coil tubes follows a tightly controlled multi-stage manufacturing sequence:
- Slab Preparation: Primary steel is melted in vacuum arc remelting (VAR) or electro-slag remelting (ESR) furnaces to achieve ultra-low sulfur and phosphorus content, minimizing internal crack initiation sites.
- Hot Rolling & Annealing: Billets are hot-rolled into strip and subsequently annealed in a controlled-atmosphere furnace to achieve the target austenitic or duplex microstructure with uniform grain size (ASTM grain size 6–8).
- Cold Rolling: Precision cold rolling reduces thickness to specification while developing controlled surface roughness and dimensional accuracy.
- Coil Forming: The finished strip is wound into coils of specified outer diameter with tension-controlled winding to prevent surface damage and maintain mechanical properties.
- Heat Treatment & Pickling: Post-forming solution annealing in argon or vacuum atmosphere eliminates residual stresses and restores full corrosion resistance. Acid pickling removes surface oxides and contamination.
- Quality Inspection & HIC Testing: Each production lot undergoes NACE TM0284 HIC testing, where specimens are immersed in H2S-saturated amine-impregnated 3.5% NaCl solution for 96 hours. Samples are then examined under optical microscopy (20x–100x magnification) for any evidence of cracking. Only lots achieving a Crack Index of 0 are released for sour service application.
Applications
HIC-certified stainless steel coil tubes are specified for critical sour service applications across multiple industries:
- Oil & Gas Production: Downhole tubing, casing accessories, and flow lines in H2S-containing reservoirs.
- Gas Processing Plants: Amine treating unit piping, scrubbers, and separators handling acid gas streams.
- Refining Operations: Hydrocracker and hydrotreater effluent lines exposed to dissolved hydrogen and sulfides.
- Chemical Processing: Pipelines transporting sulfur-containing compounds and acidic aqueous solutions.
- Marine & Offshore: Subsea production systems and offshore platform piping in corrosive marine environments.
Quality Certifications
Every batch of HIC-certified coil tube is accompanied by comprehensive documentation and third-party verification:
- NACE MR0175 / ISO 15156 Compliance: Full material and manufacturing qualification for sour service, including NACE MR0175 Clause 5.3.4 HIC testing per NACE TM0284.
- NACE TM0284 Test Reports: Detailed laboratory reports documenting 96-hour H2S immersion results with microscopic examination photographs and crack index calculations.
- MTC (Material Test Certificate): EN 10204 Type 3.1 mill test certificates covering chemical composition, mechanical properties, and heat treatment records.
- Third-Party Inspection: Available upon request through accredited inspection bodies (e.g., DNV, Lloyd's Register, Bureau Veritas).
- ISO 9001:2015: Quality management system certification ensuring consistent manufacturing quality and traceability.
- API Spec Q1: Quality management system for oil and gas industry supply chain, where applicable.
Unique Selling Points
Proven HIC Immunity: Unlike standard stainless steel tubing, this coil tube has been demonstrably validated through the full 96-hour NACE TM0284 H2S immersion protocol — a mandatory requirement for MR0175 sour service qualification. This eliminates the risk of catastrophic hydrogen-induced cracking failure in the field.
- Ultra-Low Impurity Metallurgy: ESR/VAR remelted grades with sulfur content below 0.003% and manganese-sulfide inclusions minimized, removing the primary crack initiation sites for HIC.
- Full Traceability: Every coil is traceable from melt heat number through final HIC test results, providing complete supply chain accountability for critical safety applications.
- Cost-Effective Coil Format: Delivered in coil form for maximum downstream processing efficiency — suitable for tube drawing, welding, and forming operations without additional cutting losses.
- Multi-Grade Availability: Selection from austenitic (304, 316, 321) to super-duplex (2507) grades provides engineers with flexibility to match specific pressure, temperature, and corrosion severity requirements.