Phosphate Sludge

Ask an Expert From: Products Finishing, ,

Posted on: 5/22/2014


Q. What is the composition of phosphate sludge from a zinc-phosphate process bath? What are the precipitates that are formed?—K.P.

A. The composition of the sludges generated in a phosphate bath varies with the type of bath in which they are produced. The composition of the sludge found in a zinc-phosphate bath is as follows:


Component Amount
Iron 20%
Zinc 8%
Phosphate as PO4 45%
Water 27%

These percentages can vary depending on the operating temperature of the bath.

The precipitates are primarily metal phosphates. Search to find a number of excellent articles on phosphating.


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