Electrolytically Polished Stainless Steel Coil Tube — Ra ≤ 0.25μm Surface Finish
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. delivers premium-grade stainless steel coil tubes featuring advanced Electrolytic Polishing (EP) surface treatment. This electrochemical finishing process achieves an industry-leading surface roughness of Ra ≤ 0.25μm by selectively dissolving microscopic protrusions on the outer surface of the tube. The result is an ultra-smooth, mirror-like finish that eliminates embedded abrasive particles and delivers the highest achievable cleanliness level for critical process applications.
Unlike mechanical polishing methods that can introduce contamination through embedded grinding media, electrolytic polishing produces a chemically clean surface free of residual particles, making it the preferred surface treatment for pharmaceutical, bioprocessing, food-grade, and semiconductor-grade tubing systems.
Material & Properties
- Base Material: 304, 304L, 316, 316L, 321, 347, and custom alloy stainless steels
- Surface Roughness (Ra): ≤ 0.25μm (0.010 mil)
- Surface Condition: Free of embedded abrasives, no mechanical contamination
- Cleanliness Level: Highest achievable — no residual grinding particles, no embedded contaminants
- Surface Chemistry: Enhanced passive chromium oxide layer formed during electrochemical dissolution
- Corrosion Resistance: Superior to mechanically polished surfaces due to intact passive film integrity
- Biocompatibility: Suitable for direct contact with pharmaceutical and medical fluids
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Surface Roughness (Ra) | ≤ 0.25 | μm (0.010 mil) |
| Embedded Abrasive Particles | None | — |
| Cleanliness Classification | Highest (Class 1) | — |
| Surface Treatment Method | Electrolytic Polishing (EP) | — |
| Treatment Scope | Outer Surface | — |
| Passive Film Integrity | Enhanced (electrochemically reinforced) | — |
| Coil Tube Form | Continuous coil configuration | — |
| Available OD Range | 3.0 – 108.0 | mm (0.12 – 4.25 in) |
| Available Wall Thickness | 0.3 – 4.0 | mm (0.012 – 0.157 in) |
| Coil Length | Up to 2,000 | m (6,562 ft) |
| Temperature Resistance | Up to 870 | °C (1,598 °F) |
Manufacturing Process
Electrolytic Polishing — Process Description
The electrolytic polishing process employed by Wenzhou Jixing Metal Materials Co., Ltd. is a precision electrochemical treatment that fundamentally differs from mechanical surface finishing methods. The process operates through the following stages:
- Pre-Cleaning: The coil tube outer surface is thoroughly degreased and cleaned to remove oils, scale, and surface contaminants prior to electrochemical treatment.
- Electrochemical Dissolution: The tube is immersed in a heated electrolyte bath and connected as the anode. An applied current causes preferential dissolution of microscopic surface protrusions — peaks, grain boundaries, and residual mechanical damage — at a faster rate than the valleys.
- Surface Leveling: Through controlled current density and temperature parameters, the surface is progressively leveled until Ra ≤ 0.25μm is achieved uniformly across the entire coil length.
- Passive Film Formation: The electrochemical environment simultaneously promotes the formation of a dense, adherent chromium oxide passive layer, enhancing long-term corrosion resistance.
- Rinsing & Drying: Post-treatment acid-free rinsing and controlled drying ensure no residual electrolyte contamination remains on the finished surface.
- Quality Verification: Each coil lot undergoes surface roughness measurement, visual inspection, and cleanliness verification to confirm compliance with specifications.
Key Advantage: Unlike mechanical polishing or passivation alone, electrolytic polishing achieves surface smoothing through electrochemical dissolution rather than mechanical abrasion. This eliminates the risk of embedded abrasive particles that can compromise surface cleanliness in pharmaceutical and medical applications.
Unique Selling Points
- Superior Cleanliness: Electrochemical dissolution ensures no embedded grinding or polishing media remains on the surface — a critical requirement for GMP-regulated environments.
- Enhanced Passive Layer: The EP process reinforces the natural chromium oxide film, providing superior and more durable corrosion resistance compared to mechanically polished surfaces.
- Uniform Surface Quality: Continuous coil configuration ensures consistent surface finish along the entire tube length without the variability associated with discrete tube processing.
- Cost-Effective Continuous Processing: Coil tube format enables high-throughput electrolytic polishing with minimal handling, reducing contamination risk and processing cost per meter.
- Regulatory Compliance: Surface finish and cleanliness levels meet or exceed requirements for pharmaceutical (GMP), food-grade (FDA 21 CFR), and semiconductor cleanroom applications.
Applications
- Pharmaceutical Processing: Bioreactors, CIP/SIP systems, fluid transfer lines, and equipment for GMP-compliant drug manufacturing.
- Medical Devices: Tubing for dialysis systems, infusion devices, and surgical instrument manufacturing.
- Food & Beverage Industry: Dairy processing, brewing, and potable water distribution systems requiring hygienic surfaces.
- Semiconductor Manufacturing: Ultra-high-purity (UHP) fluid delivery systems and cleanroom piping where particulate contamination is unacceptable.
- Chemical Processing: Corrosive fluid handling in reactors, heat exchangers, and transfer lines where enhanced passive film performance is required.
- Heat Exchangers: Coil wound heat exchangers where smooth inner/outer surfaces maximize thermal transfer efficiency and minimize fouling.
- Power Generation: Condenser tubes and steam systems requiring corrosion-resistant, low-fouling surfaces.
Quality Certifications
- ISO 9001:2015 — Quality Management System certification ensuring consistent production standards
- ISO 14001 — Environmental Management System compliance
- ISO 45001 — Occupational Health and Safety Management
- EN 10204 3.1 — Material test certificates with independent inspection
- AMS 2700 / AMS 2750 — Aerospace-grade surface finish standards (where applicable)
- 3-A Sanitary Standards — Compliance for food and dairy processing applications
- ASME BPE — Bioprocessing Equipment standards for pharmaceutical tubing
- NACE MR0175 — Resistance to sulfide stress cracking (for applicable alloy grades)
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality control throughout the electrolytic polishing process, with each production lot accompanied by comprehensive documentation including surface roughness reports, material certificates, and process parameter records to support customer audit and regulatory submission requirements.