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Phosphating: Can't dissolve zinc oxide in phosphoric acid

[editor appended this entry to this thread which already addresses it in lieu of spawning a duplicative thread]

Q. To whom it may concern, hello,

I am looking for a high quality zinc phosphate solution that has uniform coverage and good corrosion resistance and is also suitable for painting.
When I want to dissolve zinc oxide in phosphoric acid, if the amount of zinc oxide exceeds a certain limit, it is not dissolved in phosphoric acid and zinc oxide particles are scattered and precipitated in the form of white grains in the solution, and this makes the solution I don't have proper phosphate.
Ingredients I use for zinc phosphate in 100 ml volume:
Zinc Oxide 1/8 g
Phosphoric acid 4/5 g
Sodium nitrate 0/5 g

Any information on this topic will be greatly appreciated.

Amin Babak
- Mashhad, Iran
April 28, 2024

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⇩ Related postings, oldest first ⇩

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Q. Hello

I want to make zinc phosphate (coarse grain). but I have a problem with dissolving of ZnO in phosphoric acid. How can I solve it ? Which formula do you introduce me to?

best.

Mansour Kashiha
coating shop - Tehran, Iran
April 25, 2008