Zinc Phosphate stripping for coating weight

Q. Hello Community,

My company applies Henkel Zinc Phosphate on steel surfaces IAW defense specification TT-C-490. In this spec it requires us to strip the phosphate with a solution that is not stripping this coating at all. My supplier has not been able to close the gap on this and I am hoping there is some information in the community that can help.

I there a commonly used process for stripping phosphate on steel that I could use to determine this?
Is there a certain concentration i should be using for this formulation?

Spec Callout----

A.4.6 Zinc phosphate stripping (types I and V) for coating weight determination on steel. The
phosphate coating shall be completely removed by immersion in a sodium hydroxide/tetrasodium
ethylenediamine-tetraacetic acid (EDTA) solution for 15 minutes at 70 °F (21 °C). The solution
can be formulated by adding 125 grams of sodium hydroxide and 125 grams of tetrasodium EDTA
to 750 mL deionized water. Upon removal from stripping solution, rinse the samples in water, dry
the test specimens and reweigh to the nearest milligram. Repeat this process, in five minute
increments, until a constant weight is obtained.

Matt C
- Lansing Michigan
October 3, 2024

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