By Advanced Hermetic Solutions • May 23, 2025 • Surface Finishing
In the world of medical device manufacturing, especially when working with stainless steel, choosing the right surface treatment is critical to performance, biocompatibility, and longevity. Two of the most commonly applied finishing processes are passivation and electropolishing. While both aim to improve corrosion resistance and surface cleanliness, they differ in method, effect, and suitability.
Passivation is a chemical process that removes free iron and surface contaminants from stainless steel. It enhances the naturally occurring chromium-oxide layer that protects the alloy from corrosion, especially in harsh or moisture-rich environments.
Common passivation agents include nitric acid or citric acid, which selectively remove iron without affecting the underlying alloy. This process is cost-effective and widely used across various industries.
Electropolishing is an electrochemical process that removes a microscopic layer of material from a metal surface. It dissolves high points on the surface, reducing roughness, improving reflectivity, and leaving behind a smooth, sterile, and corrosion-resistant finish.
In medical applications, electropolishing is often preferred for surgical instruments, implantable devices, and tubing—components where sterility and minimal bacterial adhesion are critical.
| Feature | Passivation | Electropolishing |
|---|---|---|
| Primary Purpose | Remove free iron and contaminants | Smooth and polish surface, reduce roughness |
| Process Type | Chemical (acid-based) | Electrochemical (reverse plating) |
| Surface Appearance | Matte to slightly bright | Bright, smooth, reflective |
| Material Removal | Negligible | Yes (0.0001”–0.001”) |
| Surface Roughness (Ra) | No significant change | Significantly reduced |
| Biocompatibility | Good | Excellent |
| Cleanroom Use | Suitable | Ideal |
| Cost | Lower | Higher |
| Best For | General corrosion protection | Surgical tools, implants, tubing |
| Standards | ASTM A967, ASTM A380 | ASTM B912, SEMI F19 |
Choose passivation if your goal is to enhance corrosion resistance in general-use stainless components at low cost. For applications requiring ultra-smooth finishes, low particulate shedding, and maximum cleanliness—such as in medical, semiconductor, or aerospace use—electropolishing is often the better option.
Both processes play an important role in the medical device industry. At Advanced Hermetic Solutions, we offer both passivation and electropolishing services to meet the varying needs of our clients—backed by traceability, process control, and quality documentation.