What is Tri-cationic phosphating?

A. You should go back to Henkel and get some more advice. It is not normal at all to have an acid degreasing tank prior to Zinc Phosphating; this should be an alkali cleaning degreasing bath. Prior to Tricat phosphate it is normal to have:
alkali wash
2x rinse
conditioning rinse or conditioner spray
tricationic phosphate.

A. Dear Mr.Hamed,

Please ensure the ratio of total acid to free acid per 10 lots, also ensure accelerator concentration in the bath.
You need to maintain TA:FA ratio along with the concentration of an accelerator. This will help you for consistent results.
You can also off-line your derusting (Acid) bath for better maintenance of your phosphate bath.

A. More words please, Mr. Biabani. I don't understand even very generally what you are doing yet, let alone any of your details. Thanks.

A. Hi, Sunil,
A tri-cationic phosphate is one that contains ions of zinc, manganese, and nickel. There are many patents on the subject, and consequently many different formulations. The usual idea is that you buy one from your pretreatment supplier and follow the instructions on their technical data sheet. It may be possible to formulate a tri-cationic phosphate yourself, but I am not personally aware of any generic formulas. You could search expired patents. Good luck!

Regards,

A. Ah! At last somebody wants to know this! Good.

Ted is right, Actually we are manufacturers of metal pretreatment chemicals. It is a combination of 3 cations namely, ZINC, MANGANESE and NICKEL, all in a fixed combined proportion.

Technically speaking this is the best form of phosphating available. The mother liquor of such phosphating solution will be PALE GREEN, and the colour of the solution in the tank will be sea green.

This can be operated in COLD system giving excellent results, so I don't understand why people operate in hot.

Such phosphating gives excellent corrosion resistance in a salt spray chamber with low micron build up; the coating is smooth and is user friendly. Take care to maintain TOTAL ACID, and FREE ACID in the tank, and use accelerator properly.

A. Hi Mr.Sunil Juneja,

As Mr.Ted Mooney said, Tri cationic phosphate contains Zinc , Nickel & Manganese. Zinc improves adhesion , Nickel contributes to corrosion protection & Manganese improves wear resistance. There is no generic formula or chemistry available to manufacture this chemicals since there are many patents and formulations. I am sure no one will give you the formulations. Hence it is advised to discuss with pretreatment chemical supplier for the products.

Mr. Shankar Omprakash Khandelwal has referred to cold phosphating. But please understand the process time, Phosphate coating weight, Crystal structure(SEM pictures),P - ratio are not the same between cold & hot phosphates. It is the main reason mostly hot phosphate process is preferred over cold phosphating.

Thanks,

A. Hi Sunil
Tri-cation Phosphate means combination of Zn, Ni, Mg cation in phosphoric acid and chlorate; nitrate was also used in accelerator of to increase rate of reaction. TCP is preferred in hot process because of formation of required coating weight and granule size.

THANKS,

A. Sir,
Tri-cationic phosphating is based on Zn, Ni, & Mn.
The concentration of Total acid with Free acid needs to be maintained very strictly. To get better result, auto-dosing of Accelerator (on the basis of consumption/lot) needs to be procured.

A. Hi, Mitesh. Sorry, but it isn't clear to me whether you are referring tri-cationic Zn-Ni-Mn as three-in-one, or whether you mean an iron phosphate process that does cleaning/activating/phosphating in a single tank and is often called three-in-one.

But in either case, nobody will blow their trade secrets and tell you the "exact formulation" of their proprietary process. You might as well ask for the exact formulation of Coca-Cola, or the shop drawings for a Lexus :-)

But, most formulators obtain copies of all the patents in that area (which is much easier these days than in the past, since they are all on line), and formulate to the preferred embodiment of expired ones. You should also have on hand the books that explain phosphatizing in detail. Good luck.

Regards,

A. The Di-cationic is having two cations (e.g.Zinc and Calcium) while Tr-cationic is having three cations (Zinc, Nickel and Mn) in Phosphoric acid

A. Hi Sharad. Assuming that by "di-cationic" you mean zinc+nickel, rather than "calcium modified" , the advantage of the addition of manganese is probably adhesion and durability for better wear and tear performance.

Please try to actually explain your situation, and you will probably get well-directed help tailored to your situation in this forum! This forum is quite good at that, whereas broad, generalized, abstract questions usually can't be properly addressed with short answers appropriate to the forum but are answered better and with deeper insight by books.

From running this forum for 34 years now, my usual finding is that if you expect an answerer to put in more effort that the questioner you'll probably be disappointed :-)

Good luck,
Regards,