Metal finishing Q&As since 1989

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Sludge problem in phosphate bath

2003

Dear sir,

I want to know about disposal of sludge and to produce less sludge. we are doing hot zinc phosphate on wires then borax [affil links] and lime coating on the wires and then draw it, phosphate bath operate on 65-75 temp and nitrate side our problem is lots of sludge in phosphate bath and the sludge get stick on wires so we are losing our die life because of sludge and it is very difficult to disposal also. I would like to know following

1) how to dispose the sludge from hot phosphated bath it gives heavy zinc phosphate and sludge is ferric phosphate?
2) to get less sludge what precaution should be take?
3) is there any additive to be added in phosphating so that we can reduce the sludge and its stickiness so it won't stick on wires?
4) is there any phosphating chemical with less sludge and higher coating weight?

Sanjay
- Maharastra, India

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First of two simultaneous responses --

Sanjay,

I think the answer to your question goes beyond the intention of these letter pages. Why not go directly to one of the consultants you find in the consultants section of this site. I'm sure they want to help you (on a commercial basis)

Remmelt Bosklopper
- Enschede, The Netherlands
2003

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Second of two simultaneous responses --

You have to tackle the problem at the root cause, i.e., chemistry -- and your chemical supplier should be able to do it; if not change your supplier.

In the short term, you can look at the feasibility of adding a filtration loop to your phosphating bath. In automobile industry circulation and filtration are standard in the phosphating bath. A filter press in SS 304 and a immersible SS centrifugal pump should do the trick.

Hope this helps.

Gurvin Singh
Mohali, Punjab, India
2003