ISO 15730:2023

Overview

ISO 15730:2023 - "Metallic and other inorganic coatings - Electropolishing as a means of smoothing and passivating stainless steel" specifies requirements, purchaser information and test methods for electropolishing stainless steels (S2XXXX, S3XXXX, S4XXXX series and precipitation‑hardened alloys). The standard describes process controls, visual acceptance, passivation verification and reporting so finished articles achieve improved surface smoothness, hygienic cleanliness and corrosion resistance.

Key topics and technical requirements

• Scope and applicability: Electropolishing as a smoothing and passivating treatment for specified stainless steel series (see ISO 15510 for alloy composition).
• Information to be supplied by purchaser:
  • Reference to ISO 15730, alloy designation, and required test method(s)
  • Required appearance or sample (ISO 16348)
  • Acceptable electrical contact areas, dimensional tolerances
  • Passivation and test report requirements
• Process controls:
  • Preparatory cleaning or mechanical polishing as needed
  • Electropolishing in appropriate solution at specified current density, temperature and time to meet the requested finish (Annex A gives a typical solution and operating conditions)
  • Typical material removal: about 5–10 µm, up to 50 µm for additional smoothing (more at edges/corners unless shields/auxiliary cathodes used)
• Post-treatment and rinsing:
  • Removal of residual surface film by immersion in 10–30% nitric acid at room temperature or by multiple rinse stages
  • Do not use alkaline neutralization (can “set” residual film)
  • Rinse thoroughly; de‑ionized or distilled water recommended to avoid spots
• Passivation and acceptance testing:
  • Visual defect criteria: surfaces free of visible pits, striations or discoloration when viewed at ~0.5 m with 20/20 vision
  • Specified test methods: water immersion, humidity, neutral salt spray (ISO 9227), copper sulfate test, modified ferroxyl test (Clause 7)
  • Pass/fail criteria: absence of red rust, copper‑coloured deposits or rapid blueing for certain alloys
• Safety: electropolishing evolves hydrogen and oxygen gases; ensure proper ventilation and safe handling of acids and electrolytes.

Applications and who uses it

• Manufacturers and finishers performing electropolishing of stainless steel components
• Buyers/engineers specifying hygienic, low‑friction or corrosion‑resistant finishes for medical devices, food processing equipment, pharmaceutical, aerospace, and semiconductor components
• Quality/control laboratories validating passivation and surface finish per standardized test methods
• Corrosion engineers and surface‑treatment procurement teams ensuring consistent, auditable electropolishing processes

Related standards (selected)

• ISO 15510 - Stainless steel composition reference
• ISO 2064, ISO 2080 - Coating definitions and vocabulary
• ISO 4519 - Sampling procedures
• ISO 9227 - Salt spray (corrosion) tests
• ISO 16348 - Surface appearance assessment

Keywords: ISO 15730:2023, electropolishing, stainless steel, passivation, surface smoothing, electropolishing standard, passivation testing, electropolishing solution.