Metal finishing Q&As since 1989

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Zinc phosphate troubles

Dear sir,

I would like to ask you question about zinc phosphate pre-treatment. I'm facing some problem of sludge which is by product of the phosphate reaction its in form of ferric phosphate. Too much sludge generation and the nature of sludge is sticky so its damaged my wires surface when its drawing. Will you suggest an additive to less the sludge or to help out to convert that sticky nature in smooth one so I can easily wash it out with water. Waiting for your help.

Willium Dias
- Bombay, India
2003

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First of two simultaneous responses -- 2003

Hi Willium,

It is difficult to answer your question because the answer lies in the process details. Sludge formation can be controlled by altering the ration free to total acid. It is also dependent on accelerator concentration.

Check your bath parameters to ensure that they are within specification. This is the #1 cause of problems in phosphating baths because operators do not pay close enough attention to these important details. Then ask your pretreatment supplier to recommend conditions that will minimize sludge formation.

George Gorecki
- Naperville, Illinois

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Second of two simultaneous responses --

You can use calcium zinc phosphate solution. This will reduce sludge formation.

Harish Chitkara
- Chennai, Tamil Nadu, India
2003

DEAR WILLIUM,

You can remove sludge by installing a clarifier which can pump out the sludge and give clear and green soln of phosphaste which can be reused. This will also save your money.

Thanks,

NAIR VIJAYAN R
- MUMBAI, MAHARASHTRA, INDIA
2003

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2005

Dear William,

It always happens when a loss in chemical eqb is happening in your baths. Check for carry over of one bat to other. We faced a similar problem which was later corrected when we prevented carry over from Activation to Phosphating and Phosphating to Rinse.

I am sure these precautions might help you as well...!

Regards,

Mohit J Saraf
shock absorber mfgr. - Indore, India