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Pickling and Passivation
Chemical surface treatment processes where pickling removes oxide scale using acid, and passivation creates a protective chromium oxide layer to enhance corrosion resistance.
Pickling
Pickling uses a mixture of nitric acid (HNO3) and hydrofluoric acid (HF) to dissolve oxide scale, weld discoloration, and surface contamination from stainless steel.
Passivation
Passivation treats the clean surface with nitric acid or citric acid to form a uniform chromium-rich oxide layer (passive film) that provides corrosion protection.
Process Sequence
- Degreasing
- Acid pickling (40-60C, 15-30 min)
- Water rinsing
- Passivation (30-60 min)
- Final rinse and drying