What is Passivation Process , Parameter of Passivation Process , Purpose & Advantage of Passivation Process .

What Is Passivation Process (After Phosphating):-

Passivation after phosphating is a final chemical sealing treatment applied on a phosphate-coated metal surface to improve corrosion resistance and paint performance.

The phosphate layer is micro-porous; passivation seals these pores and forms a thin, protective, invisible film of Chromium Oxide , to  Preventing moisture absorption and flash rust before painting.

Passivation does not add thickness—it only stabilizes and protects the phosphate coating.

                        

Parameters of Passivation Process (After Phosphating):-

Parameter	Typical Range
Chemical Type	Chromate / Non-chromate
Bath pH	5.2 – 6.5
Temperature	35 °C or 70°C
Dip  Time	30 – 60 seconds
Concentration	As per supplier TDS
Application Method	Dip / Spray
Water Quality	DM water
Drying	Air dry or oven dry

Chemicals Used for Passivation :-

• Chromate-based passivation.
• Non-chromate / eco-friendly passivation.
• Sealer type passivation for zinc phosphate.

Why Passivation Is Required After Phosphating:-

• Phosphate coating is micro-porous
• Moisture + air can cause corrosion
• Passivation closes pores of phosphate layer
• Provides temporary corrosion protection
• Improves paint bonding and shelf life

Advantages of Passivation Process (After Phosphating):-

•  Seals Phosphate pores
•  Prevents flash rust & white rust
•  Improves corrosion resistance
•  Enhances paint adhesion
•  Increases salt spray performance
•  Improves surface uniformity

                                  

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