ASTM G48 Method F Certified Duplex & High-Alloy Stainless Steel Coil Tube
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. delivers premium-grade stainless steel coil tubes engineered for the most demanding corrosion environments in the chemical, petrochemical, oil & gas, and marine engineering sectors. Every coil tube product undergoes rigorous ASTM G48 Method F evaluation — the internationally recognized gradient temperature increase method for determining Critical Pitting Temperature (CPT) and Critical Crevice Temperature (CCT). This standardized testing protocol serves as the definitive benchmark for assessing the pitting and crevice corrosion resistance grades of duplex stainless steel and high-alloy tubing products.
Our coil tube range is designed to provide superior mechanical integrity and exceptional resistance to localized corrosion attacks, ensuring long service life in aggressive chloride-containing environments where conventional austenitic grades fail prematurely.
Material & Properties
Wenzhou Jixing Metal Materials Co., Ltd. sources and processes a comprehensive portfolio of duplex and high-alloy stainless steel grades, each qualified through ASTM G48 Method F corrosion testing:
- Duplex Grades: 2205 (UNS S31803/S32205), 2507 Super Duplex (UNS S32750/S32760), 253 Super Duplex
- High-Alloy Austenitic Grades: 904L (UNS N08904), 3105 (UNS S31050), Alloy 20 (UNS N08200), Alloy 625 (UNS N06625)
- Super Austenitic Grades: 254 SMO (UNS S31254), 254 SMO Duplex
Each grade is evaluated for:
- Critical Pitting Temperature (CPT) — minimum temperature at which pitting initiates
- Critical Crevice Temperature (CCT) — minimum temperature at which crevice corrosion initiates
- PREN (Pitting Resistance Equivalent Number) — calculated as %Cr + 3.3×%Mo + 16×%N
- Linear corrosion rate under controlled gradient heating conditions
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Form | Coil Tube (Coiltube) |
| Outer Diameter | 6.0 mm – 168.3 mm |
| Wall Thickness | 0.5 mm – 12.7 mm |
| Coil Inner Diameter | 150 mm – 400 mm (customizable) |
| Coil Length | Up to 200 m per coil (standard: 50–100 m) |
| Manufacturing Standard | ASTM A778 / ASTM A213 / EN 10217-7 |
| Surface Finish | Pickled & Passivated (2B), Bright Annealed, Custom |
| Tolerance (OD) | ±0.1 mm – ±0.5 mm (per ASTM A778) |
| Tolerance (WT) | ±10% of nominal |
| Corrosion Test Standard | ASTM G48 Method F (Gradient Temperature Increase) |
| Corrosion Test Solution | 6% NaCl / 10% HCl / 20% H₂SO₄ (per application) |
| CPT / CCT Reporting | Reported in °C with full gradient curve data |
| Packing | Wooden crate / Steel band coil / Export-grade pallet |
Manufacturing Process
The production of Wenzhou Jixing's coil tubes follows a tightly controlled, multi-stage process to ensure dimensional accuracy and metallurgical homogeneity:
- Slit Coil Preparation: High-quality cold-rolled stainless steel strip is slit to precise widths and inspected for surface defects and thickness uniformity.
- Coil Forming: Automated roll-forming equipment shapes the strip into seamless coil tubes with consistent wall thickness and roundness, minimizing residual stress.
- Welding (where applicable): TIG or laser welding with argon back-purge ensures a clean, fully fused weld seam with minimal heat-affected zone.
- Heat Treatment: Solution annealing at 1050–1150 °C followed by controlled cooling to achieve optimal grain structure and maximum corrosion resistance.
- Pickling & Passivation: Removal of scale and oxide layers, followed by passivation treatment to establish a protective chromium oxide film.
- Dimensional Inspection: Ultrasonic wall thickness gauging, OD measurement, and visual/weld inspection on 100% of production.
- Corrosion Testing: ASTM G48 Method F gradient temperature testing to determine CPT and CCT values, verifying that the material meets or exceeds the specified corrosion resistance grade.
Applications
Wenzhou Jixing's ASTM G48 Method F certified coil tubes are specified for applications where localized corrosion resistance is critical:
- Oil & Gas: Subsea pipelines, downhole tubing, heat exchangers in sour service (H₂S-containing environments), offshore platform heat transfer coils
- Chemical Processing: Reactor coils, evaporator tubes, distillation column internals, acid service heat exchangers
- Marine & Offshore: Ballast water systems, seawater cooling loops, desalination plant heat exchangers
- Pulp & Paper: Bleach liquor heat exchangers, digesters, effluent treatment coils
- Power Generation: Flue gas desulfurization (FGD) systems, condensate polishing equipment
- Food & Pharmaceutical: Hygienic heat exchanger coils requiring high corrosion resistance in chloride-rich cleaning environments
Quality Certifications & Testing
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system to ensure every coil tube product meets international standards:
- ASTM G48 Method F Testing: In-house or third-party laboratory verification of CPT and CCT values using the gradient temperature increase method — the industry gold standard for evaluating pitting and crevice corrosion resistance in duplex and high-alloy stainless steels
- ISO 9001:2015: Quality Management System certification ensuring consistent product quality and traceability
- EN 10204 3.1 / 3.2: Material test certificates with independent third-party inspection available upon request
- MTC (Mill Test Certificate): Full chemical composition, mechanical properties (tensile, yield, elongation), and hardness data provided with every shipment
- Additional Testing Available: ASTM A262 (intergranular corrosion), ASTM G48 Method B/C (potentiodynamic pitting), ASTM G102 (crevice corrosion), NACE MR0175 (sour service qualification)
Unique Selling Points
ASTM G48 Method F Certified Performance: Unlike suppliers who rely solely on PREN calculations, Wenzhou Jixing provides empirically measured CPT and CCT data for every batch, giving engineers definitive, application-specific corrosion resistance data for material selection and design margin calculations.
- Full Traceability: Every coil tube is traceable from raw material mill heat number through all manufacturing stages to final corrosion test results.
- Custom Coil Configuration: Flexible OD, wall thickness, and coil dimensions to match customer-specific heat exchanger or process equipment designs.
- Superior Localized Corrosion Resistance: Duplex and high-alloy grades with verified CPT values exceeding 50 °C (2205) and 70 °C+ (2507 Super Duplex), ensuring reliable performance in aggressive chloride environments.
- Competitive Lead Times: Efficient manufacturing and inventory management enabling rapid delivery of certified coil tube products.
- Technical Support: Dedicated metallurgical engineering team available to assist with material selection, corrosion assessment, and application-specific design reviews.
Corrosion Test Data — Representative Results (ASTM G48 Method F)
| Grade | PREN | CPT (°C) | CCT (°C) | Test Solution |
|---|---|---|---|---|
| 2205 Duplex | 34–38 | ≥ 45 | ≥ 35 | 6% NaCl, pH 2.0 |
| 2507 Super Duplex | 43–48 | ≥ 70 | ≥ 50 | 6% NaCl, pH 2.0 |
| 904L | 45–48 | ≥ 65 | ≥ 55 | 6% NaCl, pH 2.0 |
| 254 SMO | 48–52 | ≥ 80 | ≥ 65 | 6% NaCl, pH 2.0 |
| Alloy 625 | 28–32 | ≥ 60 | ≥ 50 | 6% NaCl, pH 2.0 |
Note: Values are representative and may vary by heat, manufacturing condition, and specific test parameters. Actual test reports are provided with each shipment.
Contact & Ordering
For detailed quotations, material data sheets, or ASTM G48 Method F test reports, contact Wenzhou Jixing Metal Materials Co., Ltd. Our technical team is ready to assist with specification matching, sample testing, and bulk order fulfillment for duplex and high-alloy stainless steel coil tubes.