Technical Details of Stainless Steel Polished Container Surface Treatment​​

1.Polishing Grade Standards​

Mechanical Polishing Grades​​ (per ASTM A480):

Electropolishing Grades​​ (per ASTM B912):

• o EP-Level 1​​: Ra≤0.2 μm (improved micro-smoothness)
• o EP-Level 2​​: Ra≤0.1 μm (ultra-high cleanliness requirements)

2.Mechanical Polishing Process

Process Flow​​:

Coarse grinding (60–120 grit) → Medium grinding (150–320 grit) → Fine polishing (400–800 grit) → Mirror polishing (1000+ grit)

Key Technical Parameters​​:

1. o Polishing Wheel Speed​​: 800–1800 rpm (adjusted based on abrasive grain size)
2. o Pressure Control​​: 0.1–0.3 MPa (avoid overheating and deformation)
3. o Cooling Method​​: Water/emulsion cooling (temperature <50°C)

Material Compatibility​:

1. o 304/316L​​: Suitable for all polishing grades
2. o Duplex 2205​​: Requires reduced speed to prevent σ-phase precipitation
3. o Hastelloy​​: Requires specialized polishing paste to prevent contamination

3.Electropolishing Process

Principle​​:

Anodic dissolution + passive film formation achieves micro-smoothness (removes 10–30 μm surface layer)

Electrolyte Formulations:

1. o Phosphate-based​​: H₃PO₄ 60% + H₂SO₄ 20% + H₂O 20% (for 304/316)
2. o Eco-friendly​​: Citric acid + ethylene glycol (for sensitive equipment)

Process Parameters​​:

4.Special Surface Treatments

Passivation Treatment​​ (per ASTM A967):

1. o Nitric Acid Passivation​​: 20–50% HNO₃, 40–60°C, immerse 20–60 min
2. o Citric Acid Passivation​​: 4–10% concentration, 60–80°C, eco-friendly alternative

Coating Enhancements:

1. o PTFE Coating​​: Thickness 0.2–0.5 mm, resistant to strong acids (except HF)
2. o Ceramic Coating​​: Al₂O₃ or ZrO₂, wear-resistant and high-temperature resistant

5.Quality Inspection Standards

Roughness Testing:

1. o Contact Method​​​​: Stylus profilometer (accuracy ±0.01 μm)
2. o Non-contact Method​​​​: Laser confocal microscopy (3D topography analysis)

Cleanliness Verification:

1. o Residue Test​​​​: ATP bioluminescence assay (RLU <1000)
2. o Iron Contamination Test​​​​: Potassium ferricyanide paper test (no blue spots)

Corrosion Resistance Testing:

1. o Salt Spray Test​​​​: Neutral salt spray 500 h no rust (ASTM B117)
2. o Blue Dot Test​​​​: Copper ammonium sulfate solution detects passivation effect

6.Application Scenario Selection

Pharmaceutical Industry​​:

1. o Water for Injection Tanks​​​​: Electropolishing + passivation (Ra≤0.2 μm)
2. o Fermenters​​​​: Mechanical polishing No.4 + passivation (Ra=0.3–0.5 μm)

Food Industry:

1. o Dairy Tanks​​​​: Mechanical polishing No.4 (Ra=0.3–0.5 μm)
2. o Beer Fermenters​​​​: Mechanical polishing 2B + electropolishing (Ra≤0.4 μm)

Semiconductor Industry:

1. o ​High-Purity Chemical Tanks​​​​: Electropolishing EP-Level 2 (Ra≤0.1 μm)