Metal finishing Q&As since 1989

Phosphate bath problem

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Sir,
we are using the 7 tank phosphate process but the phosphate bath turns to brownish black. for this we have tried toner addition & also urea to settled the sludge. we are facing this problem. kindly advice us.

Sager Kanitkar
- Pune
2006

Sagar, You have not indicated what type of phosphate is your bath. Brownish black is quite vague. Could help you if you can give more details.

Amit Amembal
- Mumbai, India
2006

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Hi sir
I want to know the main aim of using passivation after phosphating? because I don't use it in my plant.
and also I want ask about the chemical reaction happened in the pretreatment in epoxy "electrostatic"and curing also?
and if I can ask the same question for enameling plant?
thank you,

Dalia H. Esmat
Enamel and electrostatic powder plant - Egypt
2006

We also use 7 tank phosphating plant the best way to tackle sludge as far as I know to wash the bath after every 2 week or dependent upon your production . Their are few ways of washing bath either wash it as whole that is the throw all the chemical and refill it or to take out the chemical from the 2nd layer into another tank and throwing away the sludge only (this saves your cost of chemicals) and to take oil which comes on surface of the chemical if its let untouched for few hours out every day before starting your work that is with the help of new paper or a plain cloth if you still can't get it you can post up here again.

Rubal Sandhu
bicycle parts manufacturing unit - Ludhiana, Punjab, India
2006

adv.