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topic 1819

Q&As on Teflon (PTFE) impregnated Hard Anodizing of Aluminum p.2 of 2



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A discussion started in 1998 but continuing through 2019

December 14, 2010

RFQ: Can you Teflon Impregnate Per Mil-A-63576 [link by ed. to spec at TechStreet] 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outdated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.
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



January 29, 2014

Q. I purchase parts that are hard coat anodize with teflon impregnated IAW AMS2482 [link by ed. to spec at TechStreet] 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 probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como
and co-author of The Sulfamate Nickel How-To Guide


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

"Surface Treatment & Finishing of Aluminium and Its Alloys"
by Wernick, Pinner & Sheasby
from Abe Books
or
info on Amazon

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


September 22, 2017

A. Bob Probert's answer to the impregnation of anodizing is right on. Anodizing is built from the surface out, not like plating which puts coatings down on metal. So unless you can get the surface of the aluminum to contain conductive PTFE all bets are off. As far as getting it down into the pores--not happening. The smallest particle of PTFE is many times larger than the oxide pore. All they do with RO59 and others is dispersing the PTFE in water-borne lacquer to give it adhesion to the OXIDE. Remember, claims are easy; proving claims is the real mountain to climb

drew nosti
Drew Nosti, CEF
anodizeusa1
supporting advertiser
Ladson, South Carolina


January 8, 2018

A. While researching for a product which could be applied over HARD ANODIZE for one of our customers, I read about the positives and negatives about the PTFE. Most of this concerned the particle size. After sending 20 years as a representative for various coating companies and operating a coating distribution office for the last 20 years, I would recommend molybdenum disulfide as a way to lower the coefficient of friction on hard anodize. Without telling secrets, we were able to significantly [extend] the life cycle of hard anodize blocks which were used on guides on aerial ladders for a fire truck manufacturer.
After the hard anodize, a coating of moly was sprayed over the hard anodize and burnished at 10-15 psi using glass balls.
Since molybdenum disulfide is a crystal and becomes smaller after pressure is applied the particles will burnish into the metal and hard anodize.
There are hundreds of varieties of moly we eventually focused on an air dried with an inorganic binder. We still sell quite a bit of the material but I believe that it is even more secret than the PTFE process.

Michael Jumper
- Yeadon, Pennsylvania



September 25, 2018

Q. The usually cited TIA specification is Mil-A-63576 [link by ed. to spec at TechStreet]. It was cancelled without replacement in 1998. That specification had three types of post-anodize Teflon coating --
Type I was "impregnated" using a dip/spray and dry method.
Type II was a thermo-plastic resin coating that was actually baked on the part post-anodize.
Type III was a "thermo-setting" resin coating that was baked on after anodize.

Does anyone have any sources for those Type II or Type III thermo-plastic/setting resin coatings?

The spec that would seem to "replace" the cancelled MIL-SPEC would be AMS2482 [link by ed. to spec at TechStreet]. That spec is very light on details on either the anodic process or the Teflon application, but it has 2 application types --
Type 1 is a post-anodize coating similar to the MIL-SPEC variants.
Type 2 is a co-deposited Teflon - that is the Teflon is actually in the anodizing solution.

Does anyone have a source for any of these Type 2 Teflon additive solutions?

Mike Palatas
Gardena Specialized Processing - Gardena, California, USA



February 15, 2019

Q. Also looking to replace references to the now defunct MIL-A-63576, but I question the SAE AMS 2482 reference. Granted it is as explained above, but I find MIL-A-8625 with reference to the Hardcoat Type III. This is a bit confusing to me though, b/c TIA is supposed to be synonymous with Hardcoat Type III, but nowhere is PTFE or Teflon mentioned in 8625. Dazed & Confused

Alan Williams
- Irving, Texas, USA


February 2019

A. Hi Alan. The main issue is simply that "Type III" in one spec is not necessarily the same thing as "Type III" in another spec :-)

Type III in Mil-A-8625 [link is to free spec at Defense Logistics Agency, dla.mil] specifies 'hardcoat anodizing' which is heavy (0.002" thick) and abrasion resistant anodizing ... but (as you note) has nothing to do with 'Teflon infusion'. Type III in Mil-A-63576 [link by ed. to spec at TechStreet] had to do with the type of teflon resin and its application method.

Regards,

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



May 10, 2019

Q. How robust is the PTFE layer on this anodised aluminium? We have machine parts which are PTFE "impregnated" anodised aluminium and they are cleaned in a Meiko ware washer at 70 °C with chemicals with pH of 12 and chlorine, These parts now have a ghostly white residue and I suspect the PFTE has gone away. We have been cleaning like this for 4 years only now doing something about it. Any info is welcomed.

Paul Storrie
- Sydney, Australia


May 14, 2019

A. "Impregnation" is the wrong word, the PTFE molecule is too large to go into the anodic pores, it just lays on top. If it is too thin, as in single dip or double dip, then the pH 12 liquid breaks thru and that pH 12 will attack the aluminum, the aluminum oxide, and the sealed aluminum and make uncontrolled white aluminum oxide (white corrosion)

There has been some work done "co-occluding" PTFE into the coating, but, again, that is not "impregnation".

robert probert
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina


May 15, 2019

Q. Thank you for the reply Robert,

Is there a way to permanently remove the white aluminium oxide without further damage?

Can the PTFE layer and / or the anodised layer be reapplied to bring the parts back to "as new" condition?

Thanks.

Paul Storrie [returning]
- Sydney, Australia


May 16, 2019

A. 1. The white aluminum oxide/sulfate laying on the top can be wiped off, but the aluminum sulfate down in the pores, which pops out when heated, should have been eliminated by the anodizer by using a 5% nitric acid post dip.

2. The water dip PTFE may be reapplied if the anodizing is still there, but if the high pH washing compound has broken thru the anodic film, then you must strip and start over.

robert probert
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina


May 27, 2019

Q. Hi Robert,
Thank you for the information.

I tried to clean the white bloom with a diluted acid wash, and repeated it 5 times with a good rinse each time, but once dried the white bloom reappeared.

1) How is the anodised layer usually removed, since these parts are quite precision pieces?

2) Do you think that a process called "laser ablasion" might remove the white bloom without too much damage to the anodised layer?

Thanks again.

Paul Storrie
- Sydney, Australia


May 29, 2019

A. Before we go any further on removing the anodic film you must understand that the anodic film is 50% under the original surface and 50% on top of the original surface +/- 10%. There is no way you will EVER restore the original finish.

I do not know the "bloom", suspect it is a breakdown in the emulsion between the PTFE and the emulsifier,I think the right word is "polymerizing", call the PTFE supplier.

robert probert
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina


May 31, 2019

A. Paul

It is a long shot, but you might be able to improve the finish of the anodize by mechanical buffing / polishing by using scotchbrite (red or finer), aluminum oxide sandpaper (400 grit or finer), or using a rouge or Tripoli compound and a buff. Steel wool may also work, but is not advised.

If the anodize is thin, edges will break through to aluminum first. Go slow. If there is PTFE on the parts, the buffing will remove it.

Willie Alexander
- Green Mountain Falls, Colorado

----
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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