Electropolished 316L Stainless Steel Square Tube Ra 0.25um UHP Semiconductor Gas Line

This electropolished 316L stainless steel square tube is produced for ultra high purity gas delivery systems where a mirror bright, chemically inert bore is the difference between a clean process and a contaminated one. Starting from a fully welded and annealed ASTM A270 substrate, every tube is mechanically polished, then electrochemically processed in a controlled phosphoric and sulfuric acid bath to remove the deformed surface layer left by mechanical working. The result is an internal surface with a roughness average at or below 0.25 micron, a chromium enriched passive layer, and a bore that releases particles and moisture far more slowly than an untreated mill finish.

Because semiconductor fabs, pharmaceutical cleanrooms and analytical laboratories specify the entire gas path rather than single fittings, this tube is delivered with matched dimensional tolerance, documented weld quality and a batch traceable electropolishing record. Each production lot is tested for surface roughness at three positions along the length, residual particle count after ultrasonic cleaning, and passivation quality through a copper sulfate test. Tubes are double bagged in nitrogen purged polyethylene sleeves and end capped before crating.

• Ra 0.25 micron EP Bore: The internal surface is electropolished to a roughness average of 0.25 micron or better, reducing gas adsorption sites and cutting purge down time on high purity lines.
• Chromium Enriched Passive Layer: Electrochemical processing removes free iron and manganese from the surface, leaving a chromium oxide film with a Cr to Fe ratio above 1.5 for consistent corrosion immunity.
• Full Penetration TIG Weld: Longitudinal seams are welded without filler wire under argon shielding, then rolled and annealed so the weld bead is level with the parent metal and free from oxide scale.
• Particle and Moisture Control: Bores are ultrasonically degreased, rinsed in DI water and dried with filtered nitrogen, meeting the particle cleanliness expectations of ASTM G93 oxygen service practice.
• Tight Square Tolerance: Outer dimension is held within plus or minus 0.15 mm and corner radius within 1.5 times wall thickness, so tube seats correctly into orbital welded fittings and clamps.
• Full Traceability: Each bundle carries a heat number, mill test report to EN 10204 3.1, electropolishing batch record and roughness printout for customer quality files.

Typical installations include bulk specialty gas distribution inside semiconductor front end facilities, high purity nitrogen and argon headers in pharmaceutical sterile suites, sampling loops for analytical instruments, and clean steam condensate return lines in biotechnology plants. The square profile is chosen where engineers need a compact, stackable manifold that clamps neatly against tool frames and cleanroom wall panels, and where a round tube would leave dead space behind the equipment.

Tubes are cleaned, capped at both ends, wrapped in nitrogen purged polyethylene film and packed in fumigation free plywood crates with foam separators. Every shipment includes a dimensional inspection report, roughness measurement chart, mill test certificate and electropolishing batch sheet. We guarantee a twelve month workmanship warranty covering weld integrity and surface finish, and we support third party inspection from SGS, BV or TUV before dispatch.