Stainless Steel Coil Tube — PREN-Graded Corrosion-Resistant Solutions
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-performance stainless steel coil tubes engineered for superior pitting and crevice corrosion resistance across demanding industrial environments. Our coil tube product line is classified and specified by the internationally recognized Pitting Resistance Equivalency Number (PREN), providing engineers and procurement specialists with a transparent, quantifiable metric for selecting the optimal grade for their application.
The PREN system eliminates guesswork in material selection by consolidating the individual contributions of chromium, molybdenum, and nitrogen into a single numerical value that directly correlates with resistance to localized corrosion in chloride-containing media.
Material & Properties
The Pitting Resistance Equivalency Number is calculated using the following industry-standard formula:
PREN = %Cr + 3.3 × %Mo + 16 × %N
Each alloying element contributes to corrosion resistance in a specific manner:
- Chromium (Cr): Forms the passive chromium oxide film on the steel surface, providing baseline resistance to general and localized attack.
- Molybdenum (Mo): Significantly enhances resistance to pitting and crevice corrosion in chloride environments; its contribution is weighted at 3.3× in the PREN formula.
- Nitrogen (N): Strengthens the passive film and promotes strain-hardening; its contribution is weighted at 16× in the PREN formula, making it the most potent individual contributor per unit weight.
Our product range spans from austenitic stainless steels through duplex and super-duplex grades, offering PREN values from approximately 19 to 42, covering the full spectrum of corrosion resistance requirements.
Specifications — PREN Classification Table
| Grade | PREN Value | Typical Composition | Corrosion Resistance Level | Recommended Environment |
|---|---|---|---|---|
| 304 / 304L | ≈ 19 | 18% Cr, 8% Ni | Standard | Atmospheric, mild industrial, food processing |
| 316 / 316L | ≈ 25 | 16.5% Cr, 10.5% Ni, 2.5% Mo | High | Marine, chemical processing, pharmaceutical |
| 2205 Duplex | ≈ 35 | 22% Cr, 5% Ni, 3% Mo, 0.15% N | Very High | Offshore oil & gas, seawater systems, pulp & paper |
| 2507 Super Duplex | ≈ 42 | 25% Cr, 7% Ni, 3% Mo, 0.25% N | Extreme | Subsea production, desalination, aggressive chlorides |
Coil Tube Dimensional Specifications
| Parameter | Range / Options |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm |
| Wall Thickness | 0.3 mm – 3.0 mm |
| Coil Width | 10 mm – 150 mm (flat-rolled configurations) |
| Coil Length | Custom (typically 50 m – 500 m per coil) |
| Surface Finish | Bright annealed, pickled & passivated, matte |
| Tolerance | ±0.05 mm (OD), ±10% (wall thickness) |
Manufacturing Process
Our stainless steel coil tubes are produced through a precision-controlled manufacturing sequence:
- Slab Preparation: Vacuum arc remelting (VAR) or electro-slag remelting (ESR) ingots ensure ultra-low impurity levels and uniform chemistry.
- Hot Rolling & Annealing: Billets are hot-rolled into strip and solution-annealed to achieve full austenitic or duplex microstructure.
- Cold Reduction: Multi-stand cold rolling reduces strip to precise thickness tolerances with controlled strain rates to maintain mechanical integrity.
- Coil Forming & Sizing: Precision tube-forming equipment converts strip into seamless coil tubes with consistent wall thickness and roundness.
- Final Annealing & Passivation: Bright-bake or acid pickling followed by passivation ensures a clean, corrosion-resistant surface suitable for immediate service.
- Quality Inspection: Each coil undergoes spectrometric analysis, dimensional verification, hydrostatic testing, and corrosion testing to confirm PREN compliance.
Applications
- Heat Exchangers & Boilers: PREN ≥ 25 grades resist scaling and chloride-induced pitting in condensate and feedwater systems.
- Marine & Offshore Engineering: 2205 and 2507 duplex coil tubes withstand prolonged seawater exposure with high chloride concentrations.
- Chemical Processing: Acid-resistant coil tubes for reactors, condensers, and transfer lines handling sulfuric, hydrochloric, and phosphoric acids.
- Pharmaceutical & Food Processing: 304L and 316L coil tubes meet sanitary requirements with smooth, non-reactive surfaces.
- Desalination Plants: Super-duplex 2507 coil tubes endure high-temperature brine and hypochlorite treatment environments.
- Automotive & Aerospace: Precision-formed coil tubes for exhaust systems, fuel lines, and hydraulic circuits.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management and holds the following certifications:
- ISO 9001:2015 — Quality Management System
- ISO 14001 — Environmental Management System
- EN 10204 3.1 — Material Test Certificates
- ASTM / ASME — Conformance to ASTM A213, A269, A778, and ASME B36.19
- EN 10217-7 — European standard for austenitic and duplex stainless steel tubes
- NDT Inspection: Eddy current, ultrasonic, and radiographic testing available upon request
- Corrosion Testing: Pitting temperature (Tc) testing per ASTM G48, crevice corrosion testing per ASTM G110
Why Choose Wenzhou Jixing Metal Materials?
- PREN-Guided Selection: Our engineering team assists customers in matching the correct PREN grade to their specific service environment, optimizing cost-performance ratios.
- Full Grade Range: From standard 304L to super-duplex 2507 — one supplier for all corrosion-resistance requirements.
- Custom Manufacturing: Tailored dimensions, surface finishes, and coil configurations to meet exact project specifications.
- Traceability & Documentation: Full mill-to-plant traceability with chemical analysis, mechanical test reports, and PREN verification for every coil shipped.
- Technical Support: Access to metallurgical engineers for material selection consultation, weldability assessment, and corrosion risk analysis.