Electro-Polished Stainless Steel Coil Tube – Ra ≤ 0.25μm Surface Finish
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. offers premium-grade stainless steel coil tubes featuring an advanced Electro-Polishing (EP) surface treatment on the external surface. This high-performance product line represents the pinnacle of surface finishing technology in the stainless steel tubing industry, delivering exceptional smoothness, superior corrosion resistance, and unmatched cleanliness levels suitable for the most demanding industrial applications.
Electro-polishing is an electrochemical process that selectively dissolves microscopic surface protrusions at the atomic level, resulting in a mirror-like finish with surface roughness values as low as Ra ≤ 0.25μm. Unlike mechanical polishing methods, electro-polishing eliminates the risk of embedded abrasive particles, ensuring a chemically pure and biologically inert surface.
Material & Properties
- Base Material: Austenitic stainless steel grades including 304, 304L, 316, 316L, 321, and custom alloy compositions
- Surface Finish: Electro-Polished (EP) – external surface treatment
- Surface Roughness: Ra ≤ 0.25μm (microfinish quality)
- Corrosion Resistance: Enhanced passive layer formation due to electrochemical passivation
- Cleanliness: Highest achievable cleanliness level – no embedded abrasive contamination
- Hygiene: FDA-compliant, suitable for sanitary and pharmaceutical applications
- Mechanical Properties: Maintains full tensile and yield strength of base material with minimal wall thinning
Technical Specifications
| Parameter | Specification | Standard / Method |
|---|---|---|
| Surface Roughness (Ra) | ≤ 0.25μm | ISO 4287 / ASME B46.1 |
| Maximum Embedded Abrasive | None (Zero tolerance) | Visual & Microscopic Inspection |
| Surface Cleanliness | Highest Grade – Chemical Purity | ISO 14644 Cleanroom Classification |
| Passive Layer Thickness | Enhanced (2–5 nm typical) | XPS / Electrochemical Analysis |
| Wall Thinning (EP Process) | 0.01–0.05 mm (controlled) | Ultrasonic Thickness Measurement |
| Tube Form | Coil Tube (Continuous Coil) | Custom Lengths Available |
| Available Grades | 304, 304L, 316, 316L, 321, 904L | ASTM A213 / A269 |
| Welding Quality | Full Penetration – EP Compatible | ISO 3834 / ASME BPE |
Manufacturing Process
Electro-Polishing (EP) Process Detail
The electro-polishing process employed by Wenzhou Jixing Metal Materials Co., Ltd. utilizes controlled electrochemical dissolution to achieve superior surface quality through the following mechanism:
- Pre-Treatment: Coil tubes undergo rigorous degreasing, pickling, and passivation to remove all surface contaminants and oxide layers prior to polishing.
- Electrochemical Dissolution: The tube surface is immersed in a heated electrolyte bath (typically phosphoric and sulfuric acid mixture) and subjected to a precisely controlled DC current. The process selectively dissolves microscopic surface protrusions (peaks) at the atomic level, smoothing the surface without removing significant material from valleys.
- Passive Layer Formation: The electrochemical process simultaneously thickens and strengthens the natural chromium oxide passive layer, dramatically enhancing corrosion resistance.
- Post-Treatment: Tubes are rinsed in ultra-pure deionized water (18.2 MΩ·cm) and dried in controlled cleanroom conditions to prevent re-contamination.
- Quality Verification: Each batch undergoes optical profilometry, Ra measurement, visual inspection for embedded particles, and chemical cleanliness testing.
Key Process Advantages Over Mechanical Polishing
- No embedded abrasive particles – eliminates a critical contamination vector present in mechanical polishing
- Uniform surface finish across all geometries including tight coil radii
- Enhanced passive layer without additional passivation steps
- Reduced risk of surface stress cracking
- Reproducible, automated process with tight statistical control
Applications
- Pharmaceutical & Biotechnology: Drug delivery systems, bioreactor tubing, sterile fluid transfer lines, and CIP/SIP-compatible process piping
- Food & Beverage: Dairy processing equipment, brewing systems, hygienic fluid handling, and food-grade transfer coils
- Semiconductor Manufacturing: Ultra-pure chemical delivery systems, etchant transfer lines, and high-purity gas handling
- Medical Devices: Implant-compatible tubing, dialysis equipment, and sterilization-resistant medical components
- Chemical Processing: Corrosive chemical transfer, acid handling systems, and high-purity solvent delivery
- Cosmetics & Personal Care: High-purity ingredient transfer and hygienic processing lines
- Heat Exchangers: High-efficiency heat transfer coils requiring low-fouling surfaces
- Research & Laboratory: Precision analytical equipment, chromatography systems, and metrological instruments
Quality Certifications & Standards Compliance
- ISO 9001:2015 – Quality Management System Certification
- ISO 14001 – Environmental Management System
- ASME BPE – Bioprocessing Equipment Design & Fabrication (where applicable)
- 3-A Sanitary Standards – Approved for food-grade applications
- FDA 21 CFR – Compliant for food and pharmaceutical contact
- CE Marking – European conformity for machinery directives
- ASTM A213 / A269 – Seamless and welded stainless steel tube standards
- ISO 4287 – Surface texture measurement compliance
- ISO 14644 – Cleanroom classification for final processing environment
Unique Selling Points
Why Choose Electro-Polished Coil Tubes from Wenzhou Jixing Metal Materials?
- Highest Cleanliness Grade: The electro-polishing process inherently eliminates embedded abrasive contamination – a critical advantage over mechanical finishing methods that cannot guarantee zero particle embedment.
- Ra ≤ 0.25μm Surface Quality: Achieves true microfinish smoothness that minimizes bacterial adhesion, reduces fluid friction losses, and prevents particulate generation in service.
- Enhanced Corrosion Performance: The thickened passive oxide layer provides superior resistance to pitting, crevice corrosion, and stress corrosion cracking compared to conventionally finished surfaces.
- Continuous Coil Format: Delivered in coil configuration for maximum fabrication flexibility, reduced splicing requirements, and seamless integration into automated manufacturing lines.
- Process Integrity: Electro-polishing does not introduce residual stresses, work hardening, or geometric distortion – preserving the mechanical properties of the base material.
- Full Traceability: Each coil lot is accompanied by material certification (EN 10204 3.1/3.2), surface finish reports, and chemical analysis documentation.
Technical Support & Customization
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including:
- Custom coil tube specifications – outer diameter, wall thickness, and length tailored to customer requirements
- Surface finish verification reports with optical profilometry data
- Material certifications and traceability documentation per EN 10204
- Engineering consultation for application-specific surface finish requirements
- Sample availability for customer qualification and validation
- Flexible MOQ and production lead time options
For detailed quotations, technical data sheets, or sample requests, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Our engineering team is available to assist with material selection, specification development, and application engineering support.