Stainless Steel Coil Tube — Chemical Degreasing (Alkaline Circulation Flushing) for Inner Surface Treatment
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product supplied in continuous coil form, optimized for downstream forming, bending, and processing applications. The chemical degreasing process described herein pertains specifically to the inner surface treatment (Internal Surface Degreasing), which constitutes a critical post-manufacturing step within the surface finishing sequence.
Chemical degreasing via alkaline cleaning agent circulation flushing (Alkaline Detergent Circulation Flushing) is employed to thoroughly remove residual organic contaminants—including rolling oils, drawing lubricants, emulsions, and other process-induced organic residues—from the inner bore of the stainless steel coil tube. This ensures the material meets stringent cleanliness requirements for hygienic, pharmaceutical, food-grade, and high-purity industrial applications.
Material & Properties
- Base Material: Austenitic and/or duplex stainless steel (e.g., AISI 304, 304L, 316, 316L, 321, 310S, 904L, 2205, 2507), conforming to ASTM, EN, GB, or JIS standards.
- Form: Seamless or welded coil tube (Coiltube), supplied in continuous coil configuration for high-volume processing efficiency.
- Surface Finish (Post-Degreasing): Clean, oil-free inner surface with no visible organic film; ready for subsequent passivation, electropolishing, or direct use.
- Key Properties: Corrosion resistance, mechanical strength, weldability, and dimensional precision are preserved throughout the degreasing process without surface attack or material degradation.
Specifications
| Parameter | Specification / Range |
|---|---|
| Process Type | Chemical Degreasing — Alkaline Circulation Flushing |
| Target Surface | Inner Surface (Internal Bore) |
| Cleaning Agent | Alkaline detergent solution (pH 12–14) |
| Operating Temperature | 50°C – 80°C (122°F – 176°F) |
| Residual Oil Removal | < 0.1 mg/cm² (per ASTM B342 / GB/T 21984) |
| Contaminants Removed | Rolling oil, drawing oil, emulsions, waxes, and other organic residues |
| Residual Alkalinity | Neutralized to pH 6.5–8.5 post-rinse |
| Applicable Standards | ASTM B342, EN ISO 14509, GB/T 21984, GB/T 4237 |
| Post-Treatment Compatibility | Compatible with passivation, electropolishing, pickling, and mechanical finishing |
| Coil Weight | Typically 1,000 kg – 3,000 kg per coil (configurable) |
Manufacturing Process
The chemical degreasing of the inner surface of the stainless steel coil tube is executed through a multi-stage alkaline cleaning agent circulation flushing process. The methodology is as follows:
- Pre-Inspection & Loading: The stainless steel coil tube is inspected for surface condition and loaded onto the processing line. Tubes are oriented to ensure full internal exposure to the cleaning medium.
- Alkaline Solution Preparation: A concentrated alkaline detergent solution (typically sodium hydroxide-based or sodium carbonate-based with surfactants and chelating agents) is prepared at a controlled pH of 12–14 and heated to the operating temperature range of 50°C–80°C.
- Circulation Flushing: The heated alkaline solution is circulated through the internal bore of the coil tube at controlled flow rates, ensuring uniform contact with the entire inner surface. The circulation system maintains consistent temperature and chemical concentration throughout the process.
- Soaking & Emulsification: During circulation, the alkaline solution emulsifies and saponifies organic residues—rolling oils, drawing lubricants, and emulsions—breaking them down into water-soluble micelles that are carried away by the flow.
- Rinsing: Following the degreasing cycle, the tube is rinsed with clean water (deionized or softened) to remove all traces of alkaline solution and emulsified contaminants.
- Neutralization & Final Rinse: A neutralizing rinse (dilute acid or buffered solution) may be applied to ensure the surface pH is within the neutral range (pH 6.5–8.5), preventing residual alkalinity.
- Drying & Quality Verification: The coil tube is dried via air blow or controlled evaporation. Residual oil content is verified using gravimetric methods or infrared spectroscopy per ASTM B342 or equivalent standards.
Note: The circulation flushing method ensures that every section of the inner bore—including areas difficult to reach by spray application—is uniformly treated. This is particularly advantageous for coil tubes of long length, where continuous processing maintains consistency and throughput.
Applications
Stainless steel coil tubes with chemically degreased inner surfaces are indispensable in industries where internal cleanliness and surface integrity are paramount:
- Food & Beverage Industry: Hygienic piping for dairy, beer, juice, and pharmaceutical-grade fluid transport (conforming to FDA and 3-A standards).
- Pharmaceutical & Biotechnology: CIP/SIP-compatible tubing for cleanroom fluid systems, chromatography, and bioreactor connections.
- Semiconductor & Ultra-Pure Systems: High-purity water and chemical delivery lines requiring minimal particulate and organic contamination.
- Chemical Processing: Corrosive fluid transfer lines where organic residue buildup could compromise product purity.
- Medical Devices: Tubing for medical gas delivery, dialysis equipment, and implant manufacturing processes.
- Downstream Processing: Pre-treatment for electropolishing, passivation, or coating applications where a clean substrate is essential.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification ensuring consistent process control and traceability.
- ISO 14001 — Environmental Management System, governing the handling and disposal of alkaline cleaning solutions.
- ASTM B342 — Standard Test Method for Determination of Oil and Grease Residue on Metal Surfaces.
- EN ISO 14509 — Steel tubes and pipes — Corrosion-resistant steels — Test methods for the determination of chromium, nickel, molybdenum, and nitrogen content.
- GB/T 21984 — Chinese national standard for surface cleanliness verification of stainless steel products.
- CE / PED Compliance — Available for pressure equipment directives where applicable.
- Mill Test Certificates (MTC) — EN 10204 Type 3.1 certificates provided with every shipment, documenting chemical composition, mechanical properties, and surface treatment parameters.
Unique Selling Points
- Complete Organic Residue Elimination: The alkaline circulation flushing process achieves residual oil levels below 0.1 mg/cm², far exceeding basic rinsing methods and ensuring true surface cleanliness.
- Inner Surface Focus: Specifically engineered for internal bore treatment—a critical differentiator for hygienic and high-purity applications where internal contamination is the primary concern.
- Continuous Coil Processing: Unlike discrete tube-by-tube cleaning methods, the circulation flushing approach accommodates full coil lengths, dramatically improving throughput and reducing handling-related contamination risks.
- Material Compatibility: The alkaline process is non-abrasive and non-etching to austenitic and duplex stainless steel microstructures, preserving surface integrity and mechanical properties.
- Scalable & Reproducible: Automated circulation systems with closed-loop temperature and pH monitoring ensure batch-to-batch consistency across production volumes.
- Environmental Responsibility: Cleaning solutions are collected, neutralized, and treated in accordance with environmental regulations, with closed-loop recycling to minimize waste.
Technical Summary
The chemical degreasing process via alkaline cleaning agent circulation flushing represents a state-of-the-art surface preparation technology for the inner surfaces of stainless steel coil tubes. By systematically removing rolling oils, drawing lubricants, and all other organic residues, this process delivers a pristine, contamination-free internal surface that meets the most demanding hygiene and purity standards. Wenzhou Jixing Metal Materials Co., Ltd. leverages this capability to supply coil tube products that serve as reliable substrates for the food, pharmaceutical, semiconductor, and chemical processing industries worldwide.