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

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,

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.

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 [on eBay or Amazon] 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.

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,

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

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.

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 / MIL-PRF-8625 [on DLA] 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 had to do with the type of teflon resin and its application method.

Regards,

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".

A. 1. The white aluminum oxide/sulphate laying on the top can be wiped off, but the aluminum sulphate 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.

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.

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.