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topic 8591

What is Sherardizing?

A discussion started in 2001 but continuing through 2018


Q. Hello

Will any body help me please? I have been waiting for a reply but none have been forthcoming!

I am an engineering student of north lindsey college England and am currently doing an assignment on corrosion of metals and the treatments that prevent these corrosions! The name of sherardizing has cropped up and I am wondering where I can find information on this process as I am currently unable to find an amount of quality information!

Daniel Mawbey
Student - Goole, England


A. I am also a motor engineering student in Devon. I have found a bit of info on sherardizing. Sherardizing is a diffusion process in which articles are heated in the presence of zinc dust. The process is normally carried out in a slowly rotating closed container at temperatures ranging from 320-500 °C Hope this helps.

Matthew Davis
- Newton, Abbot


Q. What is sherardizing?

Tim Cook
- Scunthorpe, England


A. It is apparently a finishing process that nobody but the British are interested in :-)
Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

Bravo, Ted.. that was too damned funny!
Marc Green
Marc Green
anodizer - Boise, Idaho


Q. I'm looking for a book related to the Sherardizing process and I didn't find any specific book in your page. Could you help me to find some good ones?

Thanks in advance,
Truly yours

Arturo Casanova
- Mexico

A. Hi Arturo. The March 2004 edition of Metal Finishing Magazine contains an article by Dr. Benu Chatterjee on sherardizing, page 40. There are a number of used and inexpensive books about Sherardizing at this link at Amazon.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


A. Sherardising, it is called. I work in a small company that sherardizes. It is a method not known very well. In 1901 Sherard Cooper founded this method in England. You put metal products, sand and zinc dust in a closed iron box. This box you put in an oven an heat it until about 410 °C. At about 380 °C. the zinc dust will melt into/onto the metal products that has to be sherardized. This method has a lot of positive things. It is better harmed to corrosion, salt spray test results are better than galvanized. In Europe only a few companies use this method. In The Netherlands one, Germany one, France two and England two or three companies. In other countries, I don't know. In US, I don't know.

Leon Kloor
- Helmond, The Netherlands

thumbs up signMy Great great Grandpa, or something, invented Sherardizing.

He was an Inventor!

Bye Love Minna

Minna Cowper-Coles
- England

The surface finishing industry hopes you will be following in his footsteps, Minna.smiley


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


Q. Leon,

I was interested in your response. I work for a small company in Australia that uses sherardising for chain components and railway clips. There is not a lot that I can find out about the subject apart from information in British and Dutch standards. One of the things that I'm interested in is the type of sand used (material, size, etc.) Can you tell me what type of sand is used and why?

Karl Keesman
- Blackburn, Victoria, Australia


A. Up to my knowledge sand is used for distribution of heat. Some two thirds of the drum have to be filled by steel or sand.

Q. Who knows something about physical basics as diffusion coefficients or metallurgic analysis of the layer. Thanks for answering.

norbert seyfert
Dr. Norbert Seyfert
surface development - Olpe, Germany


A. Sherardizing

The process of Sherardizing was founded in the early 20TH century by a gentleman whose name was Sherard Cowper-Coles.

Whilst conducting annealing trials on iron he decided to experiment by putting ZINC powder in with the iron and found that on elevated temperatures (below that of Sub Critical Annealing 723 Degs as stated by the Fe / C equilibrium diagram) a layer of diffused Zinc was formed.

With the inevitable refinement of the process Sherard commercialised the process to the extent that the Sherardizing process was born.

The main applicator of the process in the UK was a company called Zinc Alloy (clever name; as the process is the alloying of Zinc by diffusion into the base metal e.g., steel)

Zinc Alloy quickly cornered the market by offering the process in the Midlands (Wolverhampton) The North (Rochdale) and South Wales (Caerphilly) Only the Wolverhampton site still carries out the process which is now called Bodycote (surprise surprise!)

The process is eminently suitable to corrosion protecting mass produced parts and its precise coating uniformity makes it an ideal coating where Galvanizing cannot be used for fear of coating build up destroying tolerances not to mention that in the case of nuts and bolts you have to remove the galv from the nut after the process for the bolt to fit!

If you would like more info on the process do not contact as I know nothing!

Philip Stokes
- Birmingham, UK


A. FYI: since the sherardizing process was invented there were some very significant advances in the field. Today the process is creating a very hard surface (45-48 Rockwell hardness), together with extremely corrosion resistant coating. In the past it was not economical due to the lose of energy because of the sand used in the process. However, today the available systems are very economical (250 KW/1 metric ton) as they do not use sand in the process.

Dorian Shifman
- Scarsdale, New York


A. Sherardising is coming to Elk Grove. We have a lot of data on this "vapor" deposition process. Dorian is right - sand is out.

Martin Straus
- Elk Grove Village, Illinois

1998 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear Sirs:

I am looking for information on the Sherardizing process on finished machine parts. Please advise.


Gerald W [last name deleted for privacy by Editor]
- Carrollton Georgia


Hi, Gerald. As you see, we appended your inquiry to a thread which hopefully partially answers your questions.

Sherardizing is still an unusual process in the USA although it's apparently more common in England. Distek NA in Elk Grove Village, Illinois is one supplier. Lovatt Processes in Santa Fe Springs purports to be able to license the technology. If anyone knows other sources we will be happy to list them, but we don't post either testimonials or slams :-)

Good luck.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

2004 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am trying to find more than the basic outline of how sherardizing is done. We don't want to do sherardizing, but I just want to understand how it works and if there's any part that may improve our process.

Thank you,

Michael Ball
plating shop - Sittingbounre, Kent, UK


A. You could see British standard BS 4921:1988 "Specification for sherardized coatings on iron or steel" or BS 7371 -8:1998 "Coatings on metal fasteners. Specification for sherardized coatings". Good luck.

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


A. Michael,

Why don't you try contacting the Bodycote group (formerly Zinc Alloys). I know their Wolverhampton site conducts this process.

- Glasgow Scotland

February 28, 2013

A. In the 1970's I visited the UK to investigate 'Sherardizing'---it's appeal to me was that a corrosive resistant coating could be applied dry thus not creating a polluting waste water 'run off'---

The use of Silica Sand in the process acted as a carrier for the zinc powder--so I was told at the time.

I found that the lack of acceptance of the finish on parts processed this way in the U.S. was the appearance----we Americans like things 'bright and shiny' not the dull grey that is left after Sherardizing! -- hot zinc gives us that attractive finish!!

Cy Marsden
- Milwaukie, Oregon, USA

Sherardizing then zinc electroplating stainless steel nuts & washers

March 25, 2018

Q. good day ALL.
I am in need of some advice. I have a client who uses stainless steel bolts nuts & washers. He sherardizes them and then they zinc plate them thereafter!
What if anything can substitute for these two coatings on stainless steel bolts and nuts? And the zinc treatment they do after, is that merely cosmetic to eliminate the dull look?

Thanks in advance.


Anthony Diamond
Sino source - Johannesburg South Africa

March 2018

? Hi Anthony. Are you sure that you have been accurately told about the finishing process? Sherardizing stainless steel is unusual; zinc plating stainless steel is unusual; zinc plating on top of sherardizing is unusual. So sequentially sherardizing and then zinc electroplating stainless steel nuts & washers is something I've not heard of :-)
Hopefully another reader will clue us in.

As for what can 'substitute' for it, you'd need to tell us the exact application and why the process is being done.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

Chromating a zinc-alloy thermal diffusion coating

June 22, 2018

Q. Good morning. I am working with an applicator who specializes in thermal diffusion coatings. I am not too familiar with this process. What I do know is that parts are placed in a large rotating vat, along with a proprietary zinc powder and other powdered material. The vat then heats up and slowly rotates as the powder melts and is then melted into the substrate of the parts. This results in a zinc-alloy coating. The customer I am working with provides a coating that is mostly zinc, with some iron and aluminum also in the coating. Does anyone have experience with applying trivalent passivates and sealers typically used over electroplated zinc coatings over a thermal diffusion coating? The customer is seeking additional corrosion protection as well as a black appearance. I tried using our trivalent black passivate, utilizing a nitric pre-dip and it did not take.

Any suggestions would be much appreciated.

Thank you.

Dustin Shoaf
Technical Representative - Brunswick, Ohio, United States

June 26, 2018 2nd Request

Q. I am trying to apply a trivalent black passivate + sealer to some panels that contain a thermal diffusion coating. The diffusion coating process consists of parts or panels placed into a large retort along with a proprietary zinc metal powder. The retort is heated and slowly rotates as the metal atoms in the powder bond with the part surface. At the end, the coating is mostly zinc with some iron and aluminum and is typically 20 - 30 microns thick. I am having trouble getting the black passivate to react to with the coating. Does anyone have any experience with this? We have successfully applied a traditional thick layer passivate as indicated through improved salt-spray testing. However, I am having difficulty with the black.

Thank you.

Dustin Shoaf [returning]
Technical Representative - Brunswick, Ohio, United States

July 2018

A. Hi Dustin. I wouldn't know how to formulate a passivate for Sherardizing, but Anthony's question about zinc plating on top of sherardizing, plus the knowledge that zinc die castings are sometimes zinc electroplated to allow better chromating, can at least give you food for thought towards that possibility. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

Threads on similar topics include:
- Letter 4917, "Sherardising: What is it? What are the important parameters?"
- Letter 18257, "What is Distek / DiAv-93 / Unstain 1500 Thermodiffusion Sherardizing"

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