Passivation of Stainless Steel
- Passivation of stainless steel is a chemical process that enhances its corrosion resistance by removing free iron and forming a passive oxide layer. This layer protects the underlying metal from oxidation and corrosion in harsh environments.
* Passivation Process Steps
1. Pre-Cleaning
Remove Surface Contaminants:
Use alkaline cleaners or detergents to remove grease, oils, and dirt.
Mechanical Cleaning:
Use abrasives or brushes to eliminate heavy contamination or welding scale if present.
2. Pickling (Optional)
For heavily contaminated surfaces or after welding, pickling with acids (e.g., nitric or hydrofluoric acid mixtures) can prepare the surface.
3. Passivation
Chemical Bath:
Immerse the stainless steel in a passivation solution, typically containing nitric acid (20-50% concentration) or citric acid.
Duration:
The time varies based on the acid type, concentration, and alloy (usually 20-60 minutes).
Temperature:
Maintain a temperature of 20°C to 60°C (68°F to 140°F) for optimal results.
Citric Acid Benefits:
Eco-friendly and safer than nitric acid.
Leaves no hazardous by-products.
4. Rinsing
Rinse thoroughly with deionized or distilled water to remove residual acids.
Avoid using tap water to prevent deposition of minerals or impurities.
5. Drying
Air-dry or use clean, lint-free cloths to remove moisture.
Avoid scratching the surface during drying. # Passivation Chemical Manufacturer.
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removing free iron
