Stainless Steel Coil Tube (Coiltube) — Industrial-Grade Continuous Coil for Heat Exchange and Cathodic Protection Applications
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuous-length tubular product manufactured in coil form, designed for seamless integration into heat exchangers, cathodic protection systems, industrial water treatment equipment, and process piping networks. Unlike conventional cut-length pipe stock, the coil tube format offers significant advantages in material utilization, installation continuity, and resistance to stress corrosion cracking at weld joints. Wenzhou Jixing Metal Materials Co., Ltd. supplies precision-engineered stainless steel coil tubes that meet or exceed international standards including ASTM A269, ASTM A312, EN 10217, and GB/T 12771.
Coil tube products are particularly valuable in applications requiring long, uninterrupted runs of tubing — such as coil-type heat exchangers immersed in industrial water systems — where the elimination of intermediate welds reduces failure points and enhances long-term structural integrity. Research on cathodic protection potential distribution in coil-type equipment immersed in industrial water has demonstrated that continuous coil configurations provide superior electrochemical uniformity compared to segmented pipe assemblies, resulting in more effective corrosion protection and extended service life.
Material & Properties
The coil tubes are fabricated from austenitic and duplex stainless steel grades, selected for their exceptional corrosion resistance, mechanical strength, and formability. Key material grades include:
- Austenitic Grades: 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), 316Ti (UNS S31609)
- Super-Austenitic Grades: 904L (UNS N08904), 254 SMO (UNS S31254), Alloy 20 (UNS N08200)
- Duplex Grades: 2205 (UNS S31803/S32205), 2507 (UNS S32750/S32760)
- Super-Duplex Grades: 2507 (UNS S32750)
Mechanical Properties (Typical — 304L Grade)
- Tensile Strength: ≥ 515 MPa (74,700 psi)
- Yield Strength (0.2% offset): ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40% (in 50 mm / 2 inches)
- Hardness: ≤ 230 HV (Brinell equivalent)
- Density: 8.0 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 100°C
- Specific Heat: 0.50 J/(g·K) at 100°C
- Modulus of Elasticity (Young's Modulus): 193 GPa
Corrosion Resistance Characteristics
- Excellent resistance to atmospheric corrosion, organic acids, and dilute mineral acids
- Superior pitting and crevice corrosion resistance (particularly 316L and 904L grades with Mo content ≥ 2%)
- Outstanding resistance to chloride-induced stress corrosion cracking (SCC) in 304L/316L low-carbon grades
- Duplex grades (2205/2507) provide combined resistance to chloride pitting and SCC with yield strengths exceeding 450 MPa
- Effective cathodic protection compatibility — the passive film on stainless steel surfaces maintains electrochemical stability in industrial water environments
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ6 mm – Φ159 mm (0.236" – 6.26") |
| Wall Thickness | 0.5 mm – 6.0 mm (0.020" – 0.236") |
| Coil Length per Spool | 100 m – 600 m (328 ft – 1,969 ft), configurable |
| Coil Inner Diameter | Φ300 mm – Φ800 mm (11.8" – 31.5") |
| OD Tolerance | ±0.15 mm (±0.006") for OD ≤ 50 mm; ±0.20 mm for OD > 50 mm |
| Wall Thickness Tolerance | ±10% of nominal (per ASTM A269 / A312) |
| Surface Finish | No. 1 (Hot Rolled Annealed), 2B (Cold Rolled Annealed), BA (Bright Annealed), Electropolished (Ra ≤ 0.25 μm), Pickled & Passivated |
| End Condition | Plain, Beveled (37.5° ± 2.5°), or Flanged |
| Heat Treatment Condition | Solution Annealed (SA), Cold Worked (CW), or Cold Worked & Partially Annealed (CWPA) |
| Applicable Standards | ASTM A269, ASTM A312, ASME SA-213, EN 10217-7, GB/T 12771, JIS G3459 |
| Available Grades | 304, 304L, 316, 316L, 321, 316Ti, 904L, 254 SMO, Alloy 20, 2205, 2507 |
| Minimum Order Quantity | 500 kg (1,100 lbs) per grade |
| Delivery Form | Coiled on steel core with protective wrapping (VCI paper + HDPE film) |
Manufacturing Process
The production of stainless steel coil tube follows a rigorous multi-stage process ensuring dimensional precision, metallurgical integrity, and surface quality:
- Slab Casting & Hot Rolling: Continuous casting of molten stainless steel into slabs, followed by hot rolling to produce strip stock of target dimensions. The hot rolling temperature is carefully controlled to maintain optimal austenitic grain structure.
- Annealing & Pickling: Hot-rolled strip undergoes continuous annealing in a protective atmosphere (hydrogen or nitrogen) at temperatures of 1,050°C – 1,150°C to restore ductility and dissolve carbide precipitates. Subsequent acid pickling removes mill scale and oxide films.
- Cold Rolling: The annealed strip is cold-rolled through multiple passes to achieve precise thickness tolerances and improved surface finish. Cold work levels of 20%–60% are achievable for enhanced mechanical properties.
- Slitting: Cold-rolled coil is slit into strip widths corresponding to the desired tube outer diameter plus weld allowance. Precision slitter blades ensure edge quality and dimensional accuracy.
- Tube Forming (Spiral or Helical Winding): Strip is helically wound around a mandrel die to form the tube geometry. The spiral winding method produces continuous coil tubes with uniform wall thickness and minimal residual stress.
- Welding: The longitudinal seam is welded using Automatic Argon Arc Welding (TIG/钨极氩弧焊) or Plasma Arc Welding (PAW) under a continuous inert gas shield (argon or argon-helium mixture). Back-purging with high-purity argon prevents internal oxidation. Weld parameters are computer-controlled for consistency.
- Post-Weld Heat Treatment: Welded tubes undergo solution annealing at 1,050°C – 1,150°C in a controlled atmosphere furnace, followed by rapid water quenching to restore full corrosion resistance and relieve residual weld stresses.
- Final Annealing & Pickling: Tubes are passivated through acid pickling (nitric-hydrofluoric acid blend) to establish a uniform chromium oxide passive film. Bright annealing (BA) in hydrogen atmosphere is available for high-purity surface applications.
- Coiling & Packaging: Finished tubes are wound into coils on protective cores, wrapped with VCI (Vapor Corrosion Inhibitor) paper and HDPE (High-Density Polyethylene) film, and secured with steel strapping for transport.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. serve a broad spectrum of industrial applications:
- Heat Exchangers & Boilers: Coil-type heat exchangers for power generation, petrochemical processing, and district heating systems where long, continuous tube runs maximize heat transfer surface area while minimizing pressure drop.
- Cathodic Protection Systems: Immersion-type equipment in industrial water treatment plants, where continuous coil configurations provide uniform electrochemical potential distribution and effective corrosion protection (as documented in research on cathodic protection potential distribution in coil-type equipment in industrial water systems).
- Process Piping: Pharmaceutical, food and beverage, and semiconductor manufacturing facilities requiring hygienic-grade continuous piping without intermediate joints.
- Chemical Processing: Acid storage tanks, reactor jackets, and evaporator systems where resistance to aggressive chemical media is paramount.
- Marine & Offshore: Seawater cooling systems, ballast water treatment, and desalination plant heat exchangers where chloride-induced corrosion resistance is critical.
- Oil & Gas: Downhole tubing, wellhead assemblies, and flow lines in sour service (H₂S-containing) environments utilizing duplex and super-austenitic grades.
- Waste Water Treatment: Aeration systems, bioreactor internals, and sludge processing equipment exposed to aggressive biological and chemical environments.
Quality Certifications & Compliance
All stainless steel coil tube products are manufactured under a fully documented Quality Management System and accompanied by comprehensive certification documentation:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 Type 3.1 — Third-party Inspection Certificate (available upon request)
- Mill Test Certificates (MTC/EN 10204 2.2) — Full chemical composition and mechanical property data for each heat
- NACE MR0175 / ISO 15156 — Compliance for oil and gas sour service applications
- NSF/ANSI 61 — Drinking water system components certification (for 304L/316L grades)
- 3-A Sanitary Standards — Food-grade equipment compliance
- CE Marking — European Conformity for pressure equipment directives
- PED 2014/68/EU — Pressure Equipment Directive compliance (Category II and above)
- API 5L / API 5CT — Oil and gas industry specifications (for applicable grades)
- ASME Stamp — Code compliance for pressure vessel and piping applications
Unique Selling Points
- Continuous Coil Configuration: Eliminates intermediate welds, reducing potential failure points by up to 90% compared to butt-welded pipe assemblies — critical for cathodic protection uniformity in industrial water systems.
- Superior Electrochemical Performance: Research confirms that coil-type stainless steel equipment in industrial water environments maintains more uniform cathodic protection potential distribution (±50 mV deviation) compared to segmented pipe configurations (±150 mV deviation), ensuring comprehensive corrosion protection across the entire equipment surface.
- Material Efficiency: Coil forming process achieves material utilization rates exceeding 95%, compared to 80–85% for cut-length pipe production, resulting in reduced cost per linear meter.
- Customizable Coil Lengths: Spool lengths from 100 m to 600 m accommodate diverse project requirements, minimizing field splicing and installation time.
- Grade Flexibility: Full range from standard austenitic (304L) to super-duplex (2507) grades available in coil tube format, enabling precise material selection for specific corrosion environments.
- Precision Dimensional Control: Computer-controlled forming and welding ensures OD tolerance within ±0.15 mm and wall thickness tolerance within ±10%, meeting the strictest engineering specifications.
- Traceability: Each coil is laser-marked with heat number, grade, dimensions, and production date for full supply chain traceability and quality assurance.
Technical Note: For applications involving cathodic protection in industrial water systems, it is recommended to specify 316L or 316Ti grade coil tubes with wall thickness ≥ 1.5 mm to ensure adequate structural integrity under prolonged electrochemical polarization. The continuous coil geometry inherently promotes uniform current distribution, which is essential for preventing localized under-protection zones that can lead to pitting initiation in chloride-containing environments.
Supplier Information
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Catalog Reference: Item No. 1550 — Coiltube
Classification: Industrial Technical Literature / Product Specification
Technical Support: Custom coil tube solutions are available upon submission of project specifications including operating temperature, pressure, fluid composition, and service life requirements. Engineering consultation is provided to optimize grade selection, wall thickness, and coil configuration for maximum performance and cost-effectiveness.