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Phosphating: Can't dissolve zinc oxide in phosphoric acid

adv.
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[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

⇩ Related postings, oldest first ⇩

SUGGESTED PHOSPHATING BOOKS
(many of these are rare; the links will only sometimes work)

"Optimization of Phosphating Process" by Vinod Prasad Sharma (2022)
avail from AbeBooks, or Amazon

"Phosphating of Metals" by Werner Rausch (1991)
avail from eBay, AbeBooks, or Amazon

"Phosphating & Metal Pretreatment" by D.B. Freeman (1986)
avail from eBay, AbeBooks, or Amazon

"Phosphating of Metals" by Guy Lorin (1974)
avail from AbeBooks, or Amazon

"Electrolytic and Chemical Conversion Coatings" by Biestek & Weber (1972)
avail from AbeBooks, or Amazon

"A Study of Manganese Phosphating Reactions" by Joseph Menke (1971)
avail from AbeBooks, or Amazon

"Preparation of Metals for Painting" by Samuel Spring (1966)
avail from eBay, AbeBooks, or Amazon

"Continuous Automated Analysis and Control of phosphatizing Baths" by Edward P. Parry (1972)
avail from AbeBooks, or Amazon

(as an Amazon Associate & eBay Partner, we earn from qualifying purchases)

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

A. If you want to make zinc phosphate solution for phosphating you can use zinc phosphate not zinc oxide and the chemical contents as following:

ammonium fluoride [on eBay or Amazon] 10 g/l
zinc phosphate [on eBay ] 17 g/l
phosphoric acid [on eBay or Amazon] 300 g/l
nickel nitrate 20 g/l
ammonia [on eBay or Amazon] 8 g/l

With best regards,

Ali Gomaa
- Cairo, Egypt

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