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Q&As on Teflon (PTFE) impregnated Hard Anodizing of Aluminum




(2003)

Q. Dear Friends

Please inform me about the TEFLON Impregnation on Hard Anodised surface. How is this process done over a Hard Anodised surface?

Thanking you,

ELANGOVAN
ANODISING - COIMBATORE, TAMILNADU, INDIA


(2006)

A. You have to give all details of the application, Temperature/Service conditions and base substrate
regards,

JAYESH P SADHWANI
fluoropolymers - Mumbai, Maharashtra, India


(2006)

thumbs up signI agree that posted questions are more interesting, and help is easier to give, when details are included, Jayesh; I request the same frequently. Still, Elangovan has revealed that he is with a shop that does hard anodizing of aluminum, and is asking generally how the Teflon impregnation process process for hard anodizing is performed.

Q. For example, is it a dip process after anodizing? If so, does the hard anodizing require sealing, which is unusual for hard anodize, or does it demand that there is no sealing. Can it be done after parts have been put on the shelf, or must it be done immediately in-line? Maybe it must be sprayed on rather than dipped? Is any kind of baking for curing or for diffusion required? I too would like a general introduction to the technology. Thanks!

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



(1998)

Q. During impregnation of PTFE on Hard Anodize are the pores of the coating actually being permeated by the PTFE solution, or is this only a surface bonding?

Is the PTFE applied after anodization or is there a process by which the PTFE is included in the Anodize solution?

Is there a specific PTFE concentration requirement to comply with Type 1 of Mil-A-63576 [link by ed. to spec at TechStreet]?

Are there are any PTFE manufacturers/suppliers who understand the application for lubricative aluminum oxide coatings as spelled out in Mil-A-63576?

Can anyone answer or direct me to a source of information for these questions?

Your help is greatly appreciated.

Juan Ocampo
plating shop - San Jose, California


(1998)

A. Juan,

PTFE is applied after anodizing. Because of porous structure of anodic coating on aluminum surface, PTFE partially permeates into the micro-pores and also partially bonds the anodic coatings on surface. There are several proprietary PTFE formulations and processes available commercially in the market. To get more information, you may contact Chris Jurey at Luke Engineering and Manufacturing Co.

Ling Hao
- Grand Rapids, Michigan


(1998)

A. Information on PTFE impregnated Hardcoat will be very difficult to obtain. These processes are proprietary and closely guarded. As you discovered, even the U.S. Military was unable to obtain process information to include in MIL-A-63576. Some of the earliest work was done in the late 1950's by Luke Engineering's founder, W.P.Hayduk, in developing the Lukon 24 process. Others have developed their own procedures or tried to reverse engineer this process with varying degrees of success.. These different approaches have resulted in a number of branded products with a wide variety of application techniques, performance, and costs.

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio




(1998)

A. We do teflon Hardcoat at my shop.

A lot of companies have there own in-house proprietary processes for this finish.

My finish, as well as these proprietary named processes all meet the same specs, thus leading me to believe they are all similar and just the name is different i.e., TUFFRAM, LUKON, SINTEF, POLYLUBE, etc. You can contact the mfgr. of the teflon product we use. It is: RO-59 [Stoughton, MA]

Q. I would like to hear from some other finishers re: are their proprietary teflon hardcoat processes really special or is it all just in the name?

David A. Kraft
- Long Island City, New York


(1998)

Surface Treatment & Finishing of Aluminium and Its Alloys
Wernick, Pinner & Sheasby

!! I would be very interested in hearing from someone with a documented, scientific study or proof of an anodic coating which has had the pores impregnated with PTFE. The largest pore diameter obtainable from anodizing is phosphoric acid anodize and it is an order of magnitude smaller than the smallest particle size of PTFE.

There are processes which have the PTFE contained in the anodize solution, however, typically a dip immersion is performed or a spray application is performed after anodize.

There is an article available from Lubrication Engineering, Volume 38,8 pages 497-498, 507-509 -- which is the only documented study I have seen.

Dupont has been the best technical help to me in the past concerning PTFE coatings, they make both a solvent and a water based dispersion PTFE product used in Teflon hardcoating processes. Sizes of various anodic pore diameters are readily available in The Surface Treatment and Finishing of Aluminum and its Alloys, an oft quoted reference in the industry =>

Ward Barcafer, CEF
aerospace - Wichita, Kansas


(1998)

Q. I agree with Ward that scientific studies are needed to understand the teflon impregnation process. Of course, if the companies claiming to have knowledge of this process decide to enlighten us, then we do not need to waste time or money. As David Kraft suggested, almost all the processes seem to be similar in nature. For the past few years we have been trying to understand the pore development process on pure aluminum and its alloys, and made considerable progress on that too. Yet, it is hard to understand how teflon can be impregnated in the porous oxide layer whose diameter is less than teflon. Currently phosphoric acid is known to provide the largest pore diameter. So, unlike electrocoloring process in which the metal ions (like Cu or Ni) actually deposit within the pore walls and fill the pore, I wonder if Teflon fills up from the bottom of the pore too. Anyone willing to collaborate/fund/share knowledge on the research?

Gautam Banerjee
- Mesa, Arizona



Dupont Vydax

(1998)

Q. Does anyone know of a teflon product used in conjunction with Hardcoat Anodize called "VYDEX"?

Any info would be greatly appreciated

David A. Kraft
- Long Island City, New York


(1998)

A. Are you looking for "Vydax" (with an A not E)? It is a mixture of CFC 113 or isopropyl alcohol (at one time there were six grades available) and white wavy particles of polytetrafloroethylene (PTFE). It is a Dupont product and I'm sure you can still reach them about it.

Tom

Tom Hand
- AlliedSignal DOE



Hardcoat anodize plus Teflon for Compression Molds

(1998)

Q. Has anyone had any experience using PTFE/Hard coat on compression molds? I'm molding an amorphous polylactide at 230 °C and 150 psi and I'm looking for a hard, non-porous, tough and smooth finish with a very low coefficient of friction. I've got a sticking problem.

Thanks.

David Reichard


(1998)

A. Some time ago, I had helped solve this problem for an electronic fabricator. If no one has a better/cheaper suggestion, I would get a
1) 1st choice- PVD Chromium Nitride coating,
2) second try- PVD other nitrides, carbo-nitrides. Considering the cost of molds, PVD cost becomes acceptable in many cases.

In my project, Chromium Nitride minimized "flash" related sticking problems.

Mandar Sunthankar
- Fort Collins, Colorado



How to spec hard anodizing with teflon

(2005) -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

I am an engineer at an embroidery company that is looking for a specification to put on a drawing for a new part. The part is currently made domestically and is hard anodized with Teflon. My question is, is there a specification for this? I will be having this part manufactured overseas and I would like to avoid any problems due to lack of proper documentation on my drawing. Thanks in advance.

Kevin Fleury
Embroidery - Denver, Colorado



A. Hi Kevin. We appended your inquiry to an existing thread on that topic. As you can see, you can use specification Mil-A-63576. As you can also see though, it will take a miracle to "avoid any problems due to lack of proper documentation".

Regards,

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



(1998)

RFQ: I am interested in P.T.F.E. or MoS2 coating on anodic film.

Do you have any production line of spark anodising (micro-arc anodizing like MAGOXID-COAT) for aluminum with color? Could you introduce me to that if you have? And also tell me how to transfer that technology to my company in Korea and what kind of conditions you want?

Thank you.

Yongsoo Jeong
Yongsoo Jeong
- Changwon, Kyungnam, Korea
outdated



(1999) -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Where can I get some information on Mil-A-63576 [link by ed. to spec at TechStreet]? I am having a hard time finding info on this. Also is this teflon hard coat also called Sanford Hard Lube?

Frank DeFilippi
- Bedford, Massachusetts


(1999 - updated 2013)

A. Hi Frank, we linked your inquiry to one source for the spec. I visited Sanford Process in Natick, MA decades ago. When I last checked, Sanford Process was is Woonsocket, RI, and is now a division of Katahdin Industries. You can contact them about that Sanford Had Lube -- but there are several suppliers of teflon hard coat, not just one.

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



Revisiting "Teflon impregnated" Anodizing of Aluminum

(2000)

Q. In doing a search on this site for Teflon impregnated anodizing (TIA). I came across [the above] letter dated 1998 addressing this subject. There were several replies, but no one seemed to be able to answer the question of whether or not the Teflon actually impregnated the anodizing pores.

David Kraft mentioned a product (RO 59 ... a product I have used), which, to my understanding, is a Teflon bond, not an impregnation. In contacting Dupont, they also weren't able to answer whether the Teflon penetrated the pores of the anodic coating. So, I'd like to re-visit this subject. Has anyone been able to prove that the Teflon actually gets into the pores? I would think the only way to prove this would be using SEM photography, but I'm wondering if the cutting, and polishing, of the sample to be photographed, would smear the Teflon, making difficult, if not impossible, to see if the Teflon actually penetrated the pores? So, does TIA really exist? Or, is it a misnomer? And if it does exist, would you guys think one would get better results applying the Teflon in a dip process, or a spray process?


Marc Green
anodizer - Boise, Idaho


(2000)

A. I can't say if TIA exists. However as to testing for it ...

With an SEM it wouldn't be difficult, looking face on (not a section as you were suggesting) to focus on a pore. A simple attachment on an SEM is an EDXA (energy dispersive x-ray analysis), it gives readings of elements present. Scanning outside a pore would give readings for Aluminum, whatever it is alloyed with and oxygen (from the oxide layer), and any residue from other surface treatments. Scanning into a pore will give readings for fluorine and carbon, if the Teflon (PTFE, polytetrafluoroethylene) is present there. If there was more Teflon in the pores than on the general surface then the readings for fluorine and carbon would be that much higher there. Ian

Ian Brooke
- Scotland


(2000)

A. Sir,

A. My research yielded the statement that Teflon can NOT impregnate anodize because the smallest Teflon particle is still bigger than the largest anodize / hardcoat pore.

You may want to look at censored site - they CLAIM to do Teflon impregnation.

David A. Kraft
- Long Island City, New York

Ed. note: When this reply was printed, it could be read as either a sincere recommendation, or as sarcasm. However, after the additional replies, it seems to be a 'slam'. It is the long-standing policy of finishing.com that we do not print 'slams', so we have removed the reference.


(2000)

A. My understanding is that the Teflon particle is bigger than the anodize pore and will not fit in or "impregnate". I have interrogated several company reps at trade shows over the years who claim Teflon impregnation and received no more evidence than a smile and the assurance "oh yeah it impregnates into the pore". Maybe after we locate the Loch Ness monster and bigfoot we can put more effort into looking for evidence of Teflon impregnated anodizing.

Todd Osmolski
- Charlotte, North Carolina, USA


sidebar (2000)

Well... maybe, perhaps a representative from censored will pipe up in this forum, and offer us some proof that their coating does indeed impregnate the pores in the anodic coating...or does this indeed resemble the "sky hook" racking technique that leaves no rack marks?


Marc Green
anodizer - Boise, Idaho


(2000)

thumbs up signMy follow up reply, although a little sarcastic, was in no way meant as a "slam", towards a company whose work I have seen, and liked. However, I do believe this is a good forum, and opportunity, for a company who makes claims that appear to be impossible to share proof, that this is, indeed, possible. I'm not asking for any proprietary processes here, as a matter of fact, this could turn into a good business opportunity for a company that's willing to offer some kind of evidence to back up any claim that they are able to impregnate a PTFE coating into an anodic pore.


Marc Green
anodizer - Boise, Idaho


(2000)

Agreed, Marc! If the company that was mentioned (or any other company) wants to claim they do TIA, and defend it here, they are certainly welcome to ... and we'll be happy to put their name back on the page.

But those words were put in their mouth by someone else. We can't put their name up in lights, throw down the gauntlet, and demand that they drop everything to come running over to this forum to defend someone else's interpretation of their claims on pain of being considered 'fraidy cats.smiley

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


(2000)

A. This topic came up as a side discussion at the recent Technical Symposium of the International Hard Anodizing Association (IHAA). Two PhD scientists with metal finishing backgrounds argued opposite sides of this issue. Both offered "proof" to support their positions.

However, unlike the scientists, most of the hardcoaters present did not much care how "PTFE Impregnation" works but rather if it works and how well.

Anodizers have developed proprietary "impregnation" processes based on a variety of techniques. Little information is publicly available and there is no standardized testing to compare results. Field testing is the only foolproof method to verify the friction and wear reducing properties of each method. So it is buyer beware.

Chris Jurey
Luke Engineering & Mfg. Co. Inc.
Wadsworth, Ohio

January 28, 2012

A. Size of particles of PTFE doesn't matter when the process of impregnation is done at temperature over the melt temperature of PTFE. Over this temperature particles don't exist anymore and PTFE, depending on its molecular weight, can be liquid. But a process which does not use pressure and high temperature together cannot impregnate pores.
We apply impregnation to porous material (not aluminium) with PTFE and it really gives impervious properties to this material. Application of powder and sintering it is not an impregnation, only a superficial coating which cannot prevent pitting corrosion. Some porosities remain. When only friction properties are required, it is acceptable. When corrosion matters, it can be an issue.

Hug Christian
- Shanghai, China



December 14, 2010

RFQ: Can you Teflon Impregnate Per (Mil-A-63576 Type I) After Anodize Per Mil-A-8625 [link is to free spec at Defense Logistics Agency, dla.mil] Type II Class II Red?

Temo Z [last name deleted for privacy by Editor]
Sales - Irvine California United States
outdated


December 23, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Can anyone please narrate the PTFE impregnation process after hard anodizing?

James Martin Samson
- Coimbatore, India


December 2013

A. Hi James. As you see, we found an earlier thread to append your question to -- and it should pretty much answer it. But please follow up if you have additional questions. Thanks.

Regards,

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



January 29, 2014

Q. I purchase parts that are hard coat anodize with teflon impregnated IAW AMS 2482 Type I. In the past I received parts that were gray in color and very slick to the touch. Here recently I have gotten a few that are much darker, almost a black, and are not as smooth. I know that the coefficient of friction is supposed to be less than 0.15, but I have no way of measuring here in my shop. Any idea how "smooth" they should feel?

Thanks - Kelly

Kelly Mitchell
- Camden, Arkansas, USA


January 30, 2014

A. The Teflon is not "impregnated", although purchasing agents call it so; the molecule is too large to go into the anodic film pores, it lays on top of the coating, however it is mostly colorless, maybe partly gray tint. Your darker color comes from hard coat done under different parameters. Darker anodizing comes from lowest free acid, lowest temperature, highest current density, and is alloy dependent. Every shop uses different parameters, and within one shop all those parameters can vary unless closely controlled.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como



February 3, 2014

Q. So color is not significant, what about the 'feel'? Anything different is always flagged, and since this is supposed to be a low friction coating, it has caused some concern.

Thanks again! Kelly

Kelly Mitchell [returning]
- Camden, Arkansas, USA


October 24, 2015

A. When I worked in this field all of our Hardlube occurred after the anodization process. Mostly we hand dipped pieces straight into a 45 gallon drum of liquid hardlube and let it air dry. Sometimes we would use a paint sprayer for pieces that were too big to fit in the drum like prototypes for jet engines and flat top grills for the Navy. We even did some trial AR-15 receivers with hardlube for Bushmaster and a couple of batches of AR-15/M-16 magazines for Colt. But everything was on the surface I don't see where the PTFE could penetrate the pores or have any chance of molecularly bonding with the items as we never heated them after application and I believe it requires at least 800 degrees and a cycle of heating and cooling to get proper bonding.

George Neitz Jr
- Lecanto, Florida, USA



November 1, 2016

Q. Can two Al parts, say 6061-T6, a shaft and a bore or bushing, both be hard anodized and be treated with PTFE work well as a common bearing? I understand that no oil is needed which would imply the full bearing width is load carrying where the ratio of bearing width to bearing diameter can be low, such as below 0.20 to 0.15 w/d.

What specific loads and speeds are acceptable? What would the expected friction coefficient be? and PV value?

Would a specific load of 10 MPa (1450 psi) and velocity of 10 m/s (~2000 fpm) be workable for short durations of only 5 minutes at a time? The heat build up would not be high. Thank you for any experience in this regard.

Rolf Pfeiffer
- Toronto, ON, Canada



August 3, 2017

Q. How thick would the final coatings of Teflon impregnated anodize equal up to?

Pat Fisher
- Savannah, Georgia


August 2017

A. Hi Pat. One manufacturer of the coating material, RO-59, says 1 gallon (231 cubic inches) covers 2000 square feet, from which you can calculate the thickness. But I don't know whether you are talking about just the Teflon, or conventional anodizing (which can vary from about 0.0002" to about 0.001") plus Teflon, or hardcoat (which is about 0.002") plus Teflon, and whether you mean the thickness of the coating or the net change in dimension (anodizing consumes aluminum, so the dimensional change is only about half of the thickness of the coating. Please tell us who you are, what you do, and why you want to know so we can offer targeted help. Thanks.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"

----
Ed. note: Readers who are interested in anodized aluminum as a bearing surface might also find letter 3678, "Anodized Aluminum as a Bearing Surface", interesting.


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