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topic 0914

Testing for removal/absence of Zinc Phosphate coating


Q. I need to prove that Zinc Phosphate coating on 4000 series steel has been completely removed by grit blasting. The technique needs to be rapid (in a production environment) and highly sensitive. Any help appreciated!

Thank you!

Kenneth Graham


A. Ken,

Koslow Scientific Co in Edgewater, NJ has a kit out for testing for the presence of zinc phosphate. It might be adequate for your purpose.

James Watts
- Navarre, Florida

A. Try EMQuantIon Specific Test Strips in some procedure you devise. Perhaps they will work if you apply the reagents to the test area, and touch the strip to the resulting goo? If the metals in the steel don't interfere, which you will have to demonstrate, then it should detect very low levels of zinc. The test is designed for water samples, and you will be using drops instead of cc's of volume, which you can calculate down from the normal test volume for a sensitivity.

Available from VWR Scientific,, page 960, Cat.No. EM-10038-1, Zinc, 10-250 mg/l, Package of 100/$45.00.

pooky tom pullizi signature
Tom Pullizzi
Falls Township, Pennsylvania


A. You might want to try a spot test solution for zinc. Lead acetate is the one we always used. Zinc acetate turns black. A quick drop of the solution would tell you that zinc is still there. I'm not sure, however about the sensitivity of the method.

Craig Burkart

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Craig Burkart
- Naperville, Illinois

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