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topic 37610

Zirconium phosphatizing

A discussion started in 2005 but continuing through 2018


Q. Hello
Could you tell me something about zirconium phosphatizing.
What is this & what for?
Where can I get these chemicals?

Marek Markowski
Alumist - Poland


A. Hello, Marek. Someone will hopefully answer, but it makes for a more vibrant site if questions are posed in context. Please introduce yourself and tell us your situation. Thanks!

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


A. Zirconium phosphate is a process for bonding ceramic to various metals such as stainless steels, etc. The solution consists of 85% phosphoric acid + Zirconium oxide; or ZrPO4F + zirconium oxide.
Reference: 1994 Metals handbook Vol 5 page 472 - 474.

there is a zirconium phosphate conversion coating for aluminum. See web page:,RNWE:2004-44,RNWE:en%26sa%3DN

don baudrand
Don Baudrand
Consultant - Poulsbo, Washington

(Don is co-author of the
book "Plating on Plastics")


A. I agree with Don Baudrand.
Zirconium phosphate has been recommended for the surface pretreatment of aluminium surface.
In the US Patent US 6,312,821 B1 dated +, Takasaki et al. have described a process for improving the corrosion resistance of Al alloys in which zirconium phosphate is used to form the initial layer. According to Takasaki et al., the zirconium phosphate reacts with the oxide film on the surface of the Al alloy and forms a zirconium boehmite layer, which helps to increase the adhesion of the primer layer and the subsequent top coat.

T.S.N. Sankara Narayanan
T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at


Q. I know that zirconium phosphate is used to pre-treat surfaces before powder coating. I heard that this chemical gives splendid salt spray results on steel and Al (better than Fe-PO4 & Zn-PO4 on steel and comparable to Cr on aluminum). Is it true?

Marek Markowski [returning]
- Poland


A. This coating is new generation of layer based on microcrystaline that forms on surface. In comparison to zinc phosphate conversion coating, it has some advantage as follows:
1- No need to heat
2- No need for activation & post treatment
3- Less consumption of water
... in fact layer has good points such as environmentally friendly and excellent adhesion and resistance to corrosion.


Farshid Farzanegan

July 27, 2017

A. I have read lots of literature about it. Like you guys have mentioned, it could be used in ceramics with its properties of low swelling, high temperature resistance, wear-resistance, strong acid & strong base and so on. With all these it can improve the ceramic material's performance.

Besides this application, it also has many other applications.

If you would like to know more about it, post your questions.

Steven Zhou
- Sichuan, China

Zirconium oxide following phosphoric acid pickling

July 10, 2018

Q. My situation:I am inquiring concerning both aluminum and mild steel parts which I powder coat.

I have tried with apparent success to clean parts in a phosphoric acid solution using the "prep and etch" from the local hardware store. I rinse with distilled water and then follow with a final zirconium oxide/distilled water rinse prior to drying and then powder coating.

Now I just hope that I am doing things in a way that will not have unintended consequences later. Can anyone with knowledge in this field please tell me whether this path is advisable, or of any foreseen potential for poor long term results?

Don Decker
- Columbus Ohio

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