Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
-----
What is Sherardizing?
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2003
Q. Please provide the details regarding " SHERARDISING PROCESS ON FASTENERS & MS PLATES"
Ajay Chaudhary- nasiik, Maharashtra, Maharashtra, India
2004
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 of it that may improve our process.
Thank you,
Michael Ballplating 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, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004
A. Michael,
Why don't you try contacting the Bodycote group (formerly Zinc Alloys). I know their Wolverhampton site conducts this process.
Nigel D Gill, B.Sc. MIMF AIEMA MRSC- Glasgow Scotland
2004
A. Sherardizing is a method of batch galvanizing. It is ideal for small parts and parts that require coating of inner surfaces, although, there are systems that can do pipes as long as 12', and rail guards. The original system was quite complicated and expensive; however, today there are new systems in use which are simple, cost effective, and environmentally friendly. As far as corrosion protection, I don't know about the old systems, but the one I am familiar with is showing far superior results then any other systems I'm familiar with. Another advantage of this system is that it allows easy application of top-coats and paints.
For more information on sherardizing you can check BS EN 13811::2003 (this is the British/European Union standard).
- Charlotte, North Carolina
2006
2006
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 further!
- Birmingham, UK
Q. Many times had came came across this new surface treatment process known as Sherardized Coating. Some have even told me that this is a new technology and the SST hrs is comparable with that of Dacromet. I want to know more about this Sherardized Coating.
Daniel Tan- China
2006
Q. Dear sir,
I would like to know about sherardising as a heat treatment method. Thank you for information. Bye.
Kyambogo University - Kampala, Uganda
2006
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P.S. We edited a good number of inquiries to reflect the correct spelling of "SHERARDizing"; misspellings of this word may have given people some of the difficulty they've reported in finding info about it. Luck & Regards, Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey It's spelt sherardising with an S. Not a Z. Andy Cain- ENGLAND, United Kingdom 2007
Fortunately, the process is named after SHERARD Cowper-Coles so getting the first 7 letters right seems to be enough for google :-) Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey 2007 |
Thanks, Andy. The readers in question were leaving out the second "r". Perhaps it's spelT with an S if you are British, but it spelLED with a Z if you're American :-).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
2007
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
2008
2008
A. Readers: our podcast of October 20, 2008 begins with an interview with Martin on this subject.
Luck & Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Multiple threads merged: please forgive chronology errors :-)
Improved Sherardizing
Q. I used to work for a company that utilised the original process to sherardize conveyor chain sideplates. Now I am doing consultancy for a company that builds aluminium ingot casting plants. This company makes their own conveyor chains and they wish to sherardize the sideplates. Unfortunately, nobody else does sherardizing in Australia.
Therefore I am looking at alternative suppliers elsewhere around the world.
Could you give me the contact details of the sherardizer in the USA?
Also, if it is not a trade secret, could you tell me how they achieve such surface hardness and what do they use in lieu of sand (if any)?
Regards,
Mechanical Design Engineer - Melbourne, Victoria, Australia
February 20, 2008
A. Hello Yilmaz.
Our supporting advertisers will contact you in private regarding their ability to fill your commercial needs. There is an Israeli company that offers what they claim is an improvement on sherardizing, which they call "thermodiffusion zinc coating". Other competitive technologies that you might consider include zinc electroplating, hot dip galvanizing, and mechanical galvanizing, and zinc-rich dip-spin coating. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
February 28, 2008
A. DiSTeK (tm) is an improved Sherardizing (Sherardising) process developed in Israel (also Russia and Turkey). There is one U.S. applicator, Agritek (www.agritek.com), 4211 Hallacy Drive, Holland MI 49424 . Your contact there is Bill Maddox (WMaddox@agritek.com) 616-786-9200.
(Message from Tom Rochester : Bill Maddox, when you read this you should think about advertising on finishing.com.)
Tom Rochester
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
ASTM A1050 Zinc Powder thermo-diffusion coating -- who in USA?
Q. I seek for more information from people familiar with this process (thermal diffusion of powdered zinc). The standard ASTM specification goes into fair detail but does not answer all my questions. My interest would be for relatively thin coatings in the "Coating Class 12" (12 µm or ~0.5 mil) range.
Even more, I would like to get in touch with some North American sources for this process or variants thereof.
Thanks in advance for your input!
Thomas Hanlon, Materials Engineer
aerospace finishing - East Hartford, Connecticut, USA
June 19, 2009
Cost of Sherardizing?
Q. Can anyone provide me with information on the cost of sherardizing relative to other galvanizing processes such as hot dip. I am assuming that it is a relatively small percentage of the cost of a part whether it be a bolt or a larger parts. Any help would be appreciated.
Sam DunneEngineer - Montreal, Quebec, Canada
December 11, 2009
Why did Thermal Zinc Coating shrink my fasteners?
Q. I had a sample coat made at Distek here in South Africa and it was perfect.
Now I hand in 500 M22 x 1.5 special studs with knurl etc and they come back I cannot get the nuts on but the size over the thread and even over the head has shrunk by 0.12 mm over the thread and 0.5 over the 35 mm head. This including the actual coating.
Apparently they were not happy with the first effort and "stripped" the coating off and now I have undersized studs but with clogged threads onto which the nuts cannot go. How is this possible. Does the Thermal Zinc deposit process then shrink the material or is the heat treatment the result or what could this be.
Should I not use this method then at all which means only remaining corrosion protection would be mechanical plating to avoid hydrogen embrittlement.
Please I need advice. Previously I used just normal zinc blue electroplating giving a great finish but not as corrosion resistant and I have to trust the plater will bake all hydrogen out of the bolts and I am not sure that that is the best process.
machinist - Heidelberg, South Africa
April 16, 2010
April 30, 2010
A. Hello,
I guess you are not able to do the gauge fitment with nuts because of excess coating thickness in the thread roots. By the way what is the thread pitch and how much thickness you have deposited on it?
Maybe you can do the coating with controlled thickness and then nuts should fit easily.
All the best.
Kalyan Dhakane
Mumbai, India
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!!
- Milwaukie, Oregon, USA
February 28, 2013
Sherardizing then zinc electroplating stainless steel nuts & washers
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
Sino source - Johannesburg South Africa
March 25, 2018
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.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Chromating a zinc-alloy thermal diffusion coating
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.
Technical Representative - Brunswick, Ohio, United States
June 22, 2018
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.
Technical Representative - Brunswick, Ohio, United States
June 26, 2018 2nd Request
July 2018
A. Hi D. 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.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hello,
I am metallurgy and material engineer, I'm currently working on coating types that help to increase corrosion resistance, and I am planning to coat a few thin-short sticks with thermal diffusion coating process. I have the Zn powder and a rotating drum , but I need to find more additives for further adhesion and bonding.
Any chemical on your mind to help me ?
- Turkey Izmir
September 1, 2020
A. DiSTeK (in North America, Armorgalv) is a patented, licensed process. In Turkey, you can contact their agent -
Turkey Atalay Otomotiv. H. Rifatpasa Mah. Perpa Tic. Mer. A.Blok, K.11 No.1695 Okmeydani/ISTAMBUL Phone: (+90)212 320 31 74, Fax: (+90)212 320 31 75.
There is another thermal diffusion process supplier - Greenkote - but their market penetration has been significantly lower than DiSTeK's.
It will be difficult to catch up with over 100 years of process development, even though most of it has been in the past 20 years.
BTW, you will need extremely accurate process temperature control - probably plus or minus only a few degrees F.
Tom Rochester
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
September 14, 2020
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