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topic 39863

RoHS compliant alternative to Zinc Phosphate bond coat

A discussion started in 2006 but continuing through 2017


Q. I am in need of a RoHS compliant alternative to zinc phosphate bond coatings, are there any other process's that could replace this?

Patrick Lancor
Telecom - Naperville, Illinois, USA


A. Why would you name/suspect zinc phosphate (with a chrome free final rinse) as non-compliant with RoHS?

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


A. I agree with Mr. Ted Mooney.

In zinc phosphating process, the main concern from environmental point of view is the use of Cr(VI) compounds in the final rinse stage to seal the pores of the coating. Many chromium free final rinse solutions are available today. So why you have to look for processes other than phosphate treatment?

The following article provides an overview of the alternatives.

Phosphate after-treatment - Chrome or Non-chrome Rinses?
Product Finishing - The Journal for Surface Treatment and Engineering (U.K.), 50(4) (1997) 18-19.

However, only the chemical name of the compounds that are used as an alternative to Cr(VI) is given in this paper.

The subject is also covered in the recent review paper.

Surface pretreatment by phosphate conversion coatings -- A review
Reviews on Advanced Materials Science, 9 (2005) 130-177.

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

November 22, 2010

Q. I too am looking for a zinc phosphate coating alternative, but for different reasons. There is concern that the zinc in the coating could dissolve into the diesel fuel and clog injectors. Is there another thin coating for anti-corrosion of steel parts that is zinc free?

Justin Lewis
- El Dorado Hills, California, USA

November 22, 2010

A. Hi, Justin. Zinc is the least expensive and when you rule it out you also rule out zinc plating and galvanizing. Electroless nickel would be okay, but probably too expensive for you. How about aluminized materials or solid aluminum? Copper. tin, or nickel plating might be okay, but again expensive.


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

Want 75% gloss powder coating and no phosphate

October 13, 2017

Q. Hi Finishing Experts!

I manufacture sheet metal and often do powdercoat, textured low gloss without issues.

But I have a new client requesting a phosphate wash with a 75% gloss on a CRS and AL 5052 substrate (some weldments in assemblies)

Normally we pretreat our metal by pre-baking and can manage a 60-50% gloss this way.

My team is concerned because they think the phosphate wash is non-conformance, but it looks like that is only when Chromate 6 is used afterwards. but our application requires powdercoat, so this should be a non issue, correct?

Also, is it possible to achieve a 75% gloss without the wash?

We are trying to attain the finish as requested with lowest cost and without the need to purchase special equipment or out source services

Rob Kay
- Worcester Massachusetts USA

October 24, 2017

? Which phosphate is your customer requesting? (There are many).
What type of pretreatment do you do otherwise?

Geoff Crowleyg
- Glasgow Scotland

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