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:
|Phosphate as PO4||45%|
These percentages can vary depending on the operating temperature of the bath.
The precipitates are primarily metal phosphates. Search pfonline.com to find a number of excellent articles on phosphating.