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What is 'P ratio' in zinc phosphating bath and how to determine it?

1998

Q. Can someone tell me a method of determining the "P ratio" of a zinc phosphate conversion coating? If you know of a testing laboratory that can provide this analysis I would very much like to know of that.

Dave G [last name deleted for privacy by Editor]
Ohio

Ed. note: Sorry, this RFQ is outdated so private contact is no longer available, but public technical replies are still welcome! No public brand/source suggestions please ( huh? why?)

1998

A. ACT test lab in detroit - Assoma has an x-ray machine for coating weight.

Jeff B [last name deleted for privacy by Editor]
- Windsor , Ontario , Canada

"Phosphating of Metals"
by Werner Rausch
from Abe Books
or Amazon
[affil links]

"Phosphating & Metal Pretreatment"
by D.B. Freeman
from Abe Books
or Amazon
[affil links]

2005

Q. Can anyone throw light on P ratio in zinc phosphating bath.

Manish [last name deleted for privacy by Editor]
UL - India

2005

A. The P ratio is a measure of the forms of phosphate obtained from zinc phosphating. Miyawaki, Okita, Umehara and Okabe(1) proposed that P ratio = Phosphophyllite (Zn2Fe(PO4)2.4H2O)/[Phosphophyllite + Hopeite (Zn3(PO4)2.4H2O)].

They found that the P ratio was higher in dip applications with a low Zn:PO4.

The P ratio may be affected by a number of factors, including temperature, agitation and method of application.

(1) Miyawaki, T., Okita, H., Umehara, S., and Okabe, M., Proc. Interfinish 80, Kyoto, 1980

Brian Terry
Aerospace - Yeovil, Somerset, UK

2005

Q. 1) What exactly the definition of 'p'ratio in zinc phosphating process?
2) What should be the ratio of free acidity vs total acidity in zinc phosphating bath?

Neeraj P [last name deleted for privacy by Editor]
Generator manufacturer - Rudrapur, Uttranchal, India

2005

A. Dear Neeraj,

'P ratio' expresses quantitatively the proportion of hopeite and phosphophyllite phases in phosphate coatings. It is defined as:
Phosphophyllite
'P ratio' =
Phosphophyllite + Hopeite

The free acidity and total acidity of zinc phosphating bath depends on the formulation and operating conditions.

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

December 9, 2011

Q. Can you give me the details for how to calculate p-Ratio of phosphate bath?
We have completed SEM (Scanning Electron Microscope)for phosphate panel.

Rahul Thorat
Sr. Engineer,AME - Satara, India

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Ed. note: We appended your inquiry to a thread which hopefully answers it. Please advise of remaining questions.

Q. I want to understand ... what are the Factors effecting P-Ratio?

Can anyone help me by giving reference of some good online study material?

Have to make an Official report (Fish-Bone diagram).
I am virtually Illiterate in this Subject.

Mayank Upadhyay
- Jamshedpur, Jharkhand, INDIA
May 14, 2012

July 6, 2012

Q. I want to ask the method to determine Phosphate ion and zinc ion in Tri-cationic phosphating bath in order to monitor the coating pattern on mild steel.

Thanks and regards

neman ahmad
- lahore, Pakistan

adv.:

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