Stainless Steel Coil Tube (Coiltube) — High-Temperature Al-Based Sacrificial Anode & Coating Combined Protection System
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-formed tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed for demanding industrial environments where corrosion resistance, high-temperature performance, and mechanical integrity are paramount. This product line represents a significant advancement in stainless steel coil tube technology, integrating a proprietary High-Temperature Aluminum-Based Sacrificial Anode with Surface Coating Combined Protection System to deliver exceptional corrosion resistance under extreme operating conditions.
Coiltubes are continuous-length tubular products formed into coils, offering advantages in material utilization, handling efficiency, and downstream processing flexibility compared to straight-length pipe products. The integrated anti-corrosion technology—combining a high-temperature Al-based sacrificial anode layer with an engineered surface coating—provides a dual-mechanism protection strategy that significantly extends service life in aggressive chemical, marine, and high-temperature environments.
2. Material & Properties
2.1 Base Material Composition
The base material for the Coiltube product is austenitic stainless steel conforming to international standards including AISI 304, AISI 316L, AISI 321, and AISI 347. The high-temperature applications may also utilize 310S or custom duplex grades. The chemical composition is strictly controlled to ensure optimal corrosion resistance, mechanical properties, and weldability.
2.2 Anti-Corrosion Protection System
The core innovation of this product lies in the High-Temperature Al-Based Sacrificial Anode and Coating Combined Protection Technology:
- Sacrificial Anode Layer: A high-temperature aluminum-based alloy layer is applied to the inner and/or outer surface of the coil tube. This anode layer acts as a cathodic protection system, preferentially corroding in the presence of corrosive media to protect the underlying stainless steel substrate. The formulation is engineered to maintain electrochemical activity at elevated temperatures (up to 600°C), where conventional zinc-based anodes would fail.
- Engineered Surface Coating: A multi-layer organic-inorganic hybrid coating system provides a physical barrier against corrosive agents. The coating system includes a primer layer with strong adhesion to the metal substrate, an intermediate barrier layer for moisture and chemical resistance, and a topcoat layer providing UV stability and mechanical durability.
- Synergistic Effect: The combination of the sacrificial anode and the coating system creates a synergistic protection mechanism. The coating provides the primary barrier protection, while the sacrificial anode offers backup cathodic protection in areas where the coating may be compromised (e.g., at cut edges, scratches, or stress concentration points). This dual-protection approach results in a significantly longer service life compared to either protection method used independently.
2.3 Mechanical Properties
| Property | AISI 304 | AISI 316L | AISI 321 | AISI 347 |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥520 | ≥485 | ≥520 | ≥520 |
| Yield Strength (MPa) | ≥205 | ≥170 | ≥205 | ≥205 |
| Elongation (%) | ≥40 | ≥40 | ≥40 | ≥40 |
| Hardness (HV) | ≤200 | ≤190 | ≤200 | ≤200 |
3. Technical Specifications
| Specification Parameter | Range / Value | Standard Reference | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ325.0 mm | ASTM A554 / EN 10217 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Wall Thickness | 0.5 mm – 12.0 mm | ASTM A554 / EN 10217 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Coil Length (Continuous) | 50 m – 500 m (customizable) | — | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Coil Weight | 200 kg – 3,000 kg | — | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Surface Finish | 2B, BA, No.4, No.8, HL, Custom | ASTM A480 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Surface Coating Thickness | 80 μm – 200 μm (total multi-layer) | ISO 2808 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Al-Based Sacrificial Anode Layer Thickness | 50 μm – 150 μm |
| Property | AISI 304 | AISI 316L | AISI 321 | AISI 347 |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥520 | ≥485 | ≥520 | ≥520 |
| Yield Strength (MPa) | ≥205 | ≥170 | ≥205 | ≥205 |
| Elongation (%) | ≥40 | ≥40 | ≥40 | ≥40 |
| Hardness (HV) | ≤200 | ≤190 | ≤200 | ≤200 |
3. Technical Specifications
| Specification Parameter | Range / Value | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ325.0 mm | ASTM A554 / EN 10217 |
| Wall Thickness | 0.5 mm – 12.0 mm | ASTM A554 / EN 10217 |
| Coil Length (Continuous) | 50 m – 500 m (customizable) | — |
| Coil Weight | 200 kg – 3,000 kg | — |
| Surface Finish | 2B, BA, No.4, No.8, HL, Custom | ASTM A480 |
| Surface Coating Thickness | 80 μm – 200 μm (total multi-layer) | ISO 2808 |
| Al-Based Sacrificial Anode Layer Thickness | 50 μm – 150 μm | ISO 2808 |
| Maximum Operating Temperature | Up to 600°C (protection system active) | — |
| Corrosion Resistance (Salt Spray) | ≥1,000 hours (ASTM B117) | ASTM B117 |
| Adhesion (Cross-Cut Test) | Grade 0 (ISO 2409) | ISO 2409 |
| Impact Resistance (Pendulum Test) | ≥500 cm (no cracking) | ISO 6272 |
| Coil Tolerance (OD) | ±0.05 mm | — |
| Coil Tolerance (Wall Thickness) | ±0.02 mm | — |
4. Manufacturing Process
The production of the Stainless Steel Coil Tube with the integrated protection system involves a multi-stage, precisely controlled manufacturing sequence:
- Raw Material Selection & Inspection: High-purity stainless steel strip is sourced from certified mills, with incoming inspection including spectrographic analysis (PMI), mechanical property verification, and surface quality assessment.
- Coil Forming: Precision roll-forming or cold-drawing processes convert flat strip into tubular coil form. Advanced CNC-controlled forming equipment ensures dimensional accuracy and consistent wall thickness throughout the coil length.
- Welding (if applicable):strong> Longitudinal weld seams are created using TIG (Tungsten Inert Gas) or laser welding technology with full inert gas shielding to maintain metallurgical integrity and prevent oxidation. Weld seams are subsequently ground and polished to achieve surface uniformity.
- Surface Preparation: The formed coil tube undergoes rigorous cleaning, degreasing, and chemical etching to ensure optimal surface energy for subsequent coating adhesion. Sandblasting or chemical conversion treatments may be applied depending on the specific protection system variant.
- Al-Based Sacrificial Anode Application: The aluminum-based sacrificial anode layer is applied using specialized electro-deposition or thermal spray techniques. The process parameters (temperature, current density, alloy composition) are precisely controlled to ensure uniform thickness and consistent electrochemical properties.
- Multi-Layer Coating Application: The engineered surface coating system is applied in multiple layers using spray coating, dip coating, or electrostatic application methods. Each layer is cured at controlled temperatures to ensure proper cross-linking and adhesion.
- Quality Inspection & Testing: Comprehensive quality control includes dimensional measurement (laser scanning), coating thickness verification (eddy current or magnetic methods), adhesion testing, salt spray corrosion testing, and visual inspection for surface defects.
- Coiling & Packaging: The finished coil tube is wound onto precision cores with protective wrapping between layers to prevent inter-layer damage. Coils are packaged with moisture barrier materials and secured for transportation.
5. Applications
The Stainless Steel Coil Tube with High-Temperature Al-Based Sacrificial Anode & Coating Combined Protection is designed for the following industrial applications:
- Oil & Gas Industry: Downhole tubing, wellhead components, and subsea production systems operating in high-temperature, high-pressure (HTHP) environments with corrosive fluids.
- Chemical Processing: Heat exchangers, reactor coils, piping systems, and evaporator tubes exposed to aggressive chemical media at elevated temperatures.
- Power Generation: Boiler tubes, superheater elements, and condensate lines in fossil fuel and nuclear power plants.
- Marine & Offshore: Subsea pipelines, heat exchangers, and structural components in seawater environments where both corrosion and biofouling are concerns.
- Food & Pharmaceutical: Sanitary piping systems, pasteurization coils, and processing equipment requiring both corrosion resistance and cleanability.
- Automotive & Aerospace: Exhaust system components, turbocharger manifolds, and heat recovery systems operating at high temperatures.
- Environmental & Waste Treatment: Flue gas desulfurization systems, scrubber components, and wastewater treatment equipment.