What is the phosphating :
When Deposition of Metal phosphate like zinc phosphate, Iron
phosphate, Manganese phosphate in a acidic bath by precipitation take place
that process called phosphating .
Why we do phosphating :
Phosphating we do on steels for corrosion resistance, lubricity , or foundation coatings for subsequent coating
like powder coating, painting, oil etc.
Types of
Phosphate coating :
1. zinc phosphate :
2. Iron phosphate
3. Manganese
phosphate
4. Calcium
modified zinc phosphate
Types of
Phosphating Process :
1. Cold
phosphating : Cold zinc phosphating process is for undercoat for powder coating , paint etc. In this process coating will be medium weight between 200- 600 mg/sq feet .
2. Hot
phosphating : Hot zinc phosphating process is for Heavy zinc phosphate coating . This process we do on steel for corrosion resistance and lubricity ( To retain the oil) purpose . Coating weight may be between 1000 - 2000 mg/sq feet . In the production process it will be very difficult to monitor the coating weight of each and every peice so for quality control we can check the thickness of zinc phosphate coating which can be between 12 - 20 microns .
3. Trication
Phosphating : Trication phosphating is a microcrystal mixed metal phosphate coating having small grain and give high corrosion resistance properties. Coating weight may be between 200 - 500 mg/sq feet .
electroless nickel
boric acid free acid zinc :a cost cutting process
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