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Dry Film Lubricants: Specifications, Process and Callouts

A dry film lubricant is a thin layer of solid lubricant, usually molybdenum disulfide, graphite or PTFE, held in a binder and cured onto a blasted metal surface. Aerospace parts usually call it out by SAE AS5272 or MIL-PRF-46010 for heat cured films, MIL-PRF-81329 for extreme environments, or a sputtered MoS2 process for space mechanisms.

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Pick the specification before the product

Call out a specification and type, not just a brand name, unless the program has qualified one specific product. The specification sets cure window, minimum wear life and the temperature range the film must survive, and it requires a qualified product. A brand name alone leaves the processor free to substitute and leaves receiving with nothing to test against.

DocumentWhat it coversStatus and key numbers as published
SAE AS5272Heat cured, corrosion inhibiting solid film lubricant, qualified productsRevision G, September 2024. Type I cures within 60 minutes at 302 °F ±27 °F with 250 minutes minimum endurance life. Type II cures within 60 minutes at 400 °F ±27 °F with 450 minutes minimum. Type III is a low VOC version. Service range -90 to 400 °F
MIL-PRF-46010Heat cured, corrosion inhibiting solid film lubricant (NATO S-1738)Revision H, November 2013. Cure 1 hour at 204 °C or 2 hours at 150 °C. Range -68 to 204 °C. Endurance average 450 minutes at 1,000 lbf per a distributor summary
MIL-PRF-81329Solid film lubricant for extreme environmentsRevision E, July 2015, listed active. Range -185 to 400 °C
SAE AS1701Solid film lubricants for general or high temperature use, heat cured and air cured classesAS5272 points readers here for those applications
SAE AS5528Surface pretreatment, cure temperature and bake time for applying AS5272 filmsProcess companion to AS5272
ASTM D2625Endurance (wear) life and load carrying capacity of solid film lubricants, steel on steelCurrent edition D2625-26. Ranks films against each other, not a design value
NASA JSC PRC-8001Process specification for dry film lubricant application on JSC flight hardwareRevision F. A useful public example of a full process spec

For aerospace components, AS5272 notes that MIL-L-46010D Types I and II were superseded by AS5272 Types I and II. Older drawings still cite the MIL documents, so confirm which one your program accepts before you let a processor substitute. Type II cures hotter than Type I, which matters for tempered steels and some aluminum tempers, covered below.

MoS2, graphite and PTFE behave differently

The solid lubricant sets the friction behavior and the environment it tolerates, and the binder sets temperature range, solvent resistance and durability. Choosing one without the other is how parts end up dry and galled after thermal vacuum testing.

  • Molybdenum disulfide is the default for loaded sliding contacts. Everlube's own selection guide says MoS2 gives higher load carrying capacity and corrosion protection than graphite. It lubricates well in vacuum and dry gas but adsorbs water in humid air, which raises friction and speeds oxidation.
  • Graphite relies on adsorbed vapor, mainly water, to keep its layers sliding easily. Published tribology work shows dry conditions raise its friction, so graphite alone is a poor choice for vacuum, and a graphite bearing blend should be tested in the environment it will see.
  • PTFE gives very low friction at light loads and good release and corrosion protection, per the same Everlube guide, but it is the weaker choice for heavy contact pressure.

Binders matter as much. NASA JSC PRC-8001 notes that silicate bonded films are useful where liquid oxygen compatibility is required but are often less durable on spaceflight hardware than phenolic bonded films, and that epoxy bonded films are commonly used on ground support equipment and on bolt threads that are not meant to come apart. If the part sees oxygen service, read the oxygen compatibility guidance on the precision and oxygen cleaning page as well.

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Sputtered MoS2 for space mechanisms

Sputtered MoS2 is a vacuum deposited film roughly a tenth the thickness of a bonded film, used where clearance is tight or debris is unacceptable, such as precision bearings, gears and deployment hinges. It is a different process from spray and bake, and it needs its own process specification and witness coupons.

A NASA Glenn and Tsukuba Space Center study (NASA/TM-1999-209088) compared a bonded MoS2 film and a magnetron sputtered MoS2 film on 440C stainless steel. The published data shows how different the two are:

Property in the studyBonded MoS2Magnetron sputtered MoS2
Film thickness10 ±4 µm1.0 ±0.2 µm
Surface roughness Ra1.2 µm32 nm
Friction coefficient in humid air (about 20 percent RH)0.140.10
Wear life in humid air113,570 passes277,377 passes
Ultrahigh vacuumLower friction and longer life than the sputtered filmMet the study criteria

The practical lesson is that ground handling decides how much life a MoS2 film has left on orbit. Running a mechanism in room air adsorbs water and oxidizes the film. A 2022 NASA gear study on MoS2 coated gears stored in humid air notes that the long term effects are not fully understood and test data is limited. Plan dry storage, purge where practical, and limit the number of cycles run in air before flight.

Surface preparation decides adhesion

Bonded films hold on mechanically, so the surface must be roughened, clean and coated quickly. PRC-8001 is one of the few public process specs that spells this out, and its numbers are a reasonable benchmark when you review a processor's own procedure.

  • Design the pre-coat surface at about 32 rms or rougher on the coated feature.
  • Steel, stainless and nickel alloys are grit blasted with clean, dry alumina in the 120 to 220 mesh range. Titanium is blasted with alumina or another medium approved for titanium. Use new or clean grit, since media used on oily parts contaminates the surface.
  • Stainless and nickel alloys with over 10 percent chromium are passivated before blasting, unless every surface gets lubricant.
  • Aluminum is anodized first, Type II or Type III, then lightly glass bead blasted (size 10 beads, about 20 psi). PRC-8001 also says a materials engineer should be consulted before putting a dry film on aluminum, and that a PTFE impregnated anodic coating is often the better answer. The anodizing page covers that option.
  • After blasting, clean to pass a 30 second water break test per ASTM F22.
  • Coat within the time limit: 8 hours for aluminum, steel, stainless and nickel alloys, 4 hours for copper alloys and 2 hours for titanium, unless parts are held in controlled humidity or inert gas (titanium excepted).

Cure temperature against heat treat

Cure is a heat treatment the part did not plan for. PRC-8001 lists cures from 300 °F to 400 °F depending on product and alloy, and warns that steels tempered below the cure temperature, such as 52100 bearing steel, need an adjusted cycle. Check the cure against the temper of every substrate before you accept a Type II film. Tempering ranges are on the heat treatment page.

Thickness and fit

Most bonded films finish between 0.0002 and 0.0005 in, and PRC-8001 requires 0.0003 to 0.0005 in after burnishing for the products it lists. Everlube's guide gives the same 0.0002 to 0.0005 in range for most of its films. On a pin and bore, that is per surface, so a coated shaft in a coated hole can lose up to 0.002 in of diametral clearance.

Size the feature before coating, or state the dimension as after coating and let the machinist hold the pre-coat size. Coating both surfaces can extend life, but Everlube notes the thicker total film can deform plastically under load, so coating the softer member only is often the better choice. Films do not build evenly in bores, slots and inside radii, which is why PRC-8001 asks the drawing to mark functional surfaces and flag the rest as overspray acceptable or no film.

Measurement method should be on the PO. PRC-8001 accepts eddy current gauges, magnetic induction gauges, or the difference between pretreated and coated heights on a height gauge that reads to 0.0001 in, each result averaged over at least six readings, and it disallows micrometers. Threaded fasteners are checked for full coverage instead of thickness, and internal threads must accept at least three quarters of a turn on mating threads.

Wear life testing and lot acceptance

Qualification proves the product, and lot tests prove the application. Ask for both on the cert package.

TestPurposePublished basis
Endurance life, Falex pin and veeRanks wear life and load capacity of the lubricant productASTM D2625, referenced by AS5272. AS5272 minimums are 250 minutes (Type I) and 450 minutes (Types II and III)
Tape adhesionProves the film is bonded on each partPRC-8001 uses tape of at least 25 oz/in pulled in one motion on every part. Powder on the tape is acceptable, flakes exposing substrate are not
Solvent wipeProves a resin bonded film is fully curedPRC-8001 uses at least 50 strokes with an MEK wetted swab on a representative part per lot. Not required for silicate or epoxy films
AppearanceFinds runs, blisters, grit and bare spotsPRC-8001 requires at least 95 percent of the coating to be uniform and smooth
ThicknessConfirms fit and film lifePRC-8001 measures each part, or a random 20 percent of lots over 10 parts, going to 100 percent on any discrepancy

ASTM D2625 itself cautions that changing test conditions can change wear life and the relative ranking of films, so a Falex number is useful for comparing products, not for predicting the life of your bearing. For mechanism life, run a representative life test in the real environment, vacuum and temperature included. Facilities for that are covered on the space test lab time page.

What to call out on the drawing or PO

  • The specification, type and revision, for example AS5272 Type II, or the program process spec and the qualified product.
  • The coated surfaces, with the rest marked overspray acceptable or no film.
  • Finished film thickness after burnishing, and whether dimensions apply before or after coating.
  • Pre-coat surface roughness and the required pretreatment for each alloy, including anodize or passivation that must come first.
  • Maximum cure temperature if any substrate is tempered low, and whether burnishing is wanted (PRC-8001 burnishes by default unless the drawing says do not burnish).
  • Lot tests and records: adhesion, solvent wipe where it applies, thickness method and readings, cure chart, lubricant batch number and shelf life date.
  • For sputtered MoS2: thickness range, witness coupons run with the parts, and storage and packaging that limit humidity exposure.

Related coatings: thermal spray coatings for heavy wear, plating and cadmium alternatives for galling on fasteners, and the coatings hub. General finish callouts are on the surface finishing page.

Get dry film lubricant applied to spec

If you have parts that need AS5272, MIL-PRF-46010, MIL-PRF-81329 or a sputtered MoS2 film, send the drawing and the lubricant callout. We source the work from processors qualified for the specification, flow down pretreatment, cure limits, thickness and lot test requirements, check the cert package before parts ship, and a person replies within one business day. We can combine the machining, anodize and dry film on one purchase order. We sign a mutual NDA before files, and controlled drawings follow the process on controlled programs.

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Questions

What is the difference between AS5272 Type I and Type II?

Both are heat cured, corrosion inhibiting solid film lubricants. Per the AS5272G abstract, Type I must cure within 60 minutes at 302 °F with a 250 minute minimum endurance life, and Type II must cure within 60 minutes at 400 °F with a 450 minute minimum. Type II gives longer wear life but needs a hotter cure, so check it against the temper of steel and aluminum substrates before you specify it.

Is MIL-PRF-46010 still active, and can I use AS5272 instead?

Distributor references list MIL-PRF-46010H, dated November 2013, as the most recent revision. AS5272 states that for aerospace components the MIL-L-46010D Types I and II were superseded by AS5272 Types I and II. Many drawings still cite the military document, so ask the design authority whether AS5272 is an acceptable equivalent before allowing a substitution, and put the accepted spec and revision on the PO.

How thick is a dry film lubricant?

Most bonded films are applied to a finished thickness between 0.0002 and 0.0005 in, per Everlube's guidance, and NASA JSC PRC-8001 requires 0.0003 to 0.0005 in after burnishing for the products it lists. Sputtered MoS2 is much thinner: a NASA study measured about 1 µm on sputtered films against about 10 µm on a bonded film. Allow for the film on both mating surfaces when setting fits.

Why does MoS2 wear out faster when tested in air?

MoS2 adsorbs water vapor in humid air, which raises friction, and it oxidizes to less lubricious compounds. A NASA study found both bonded and sputtered MoS2 performed far better in vacuum and dry nitrogen than in humid air. Running a space mechanism repeatedly in room air during ground test uses up film life, so limit air cycles, store parts dry and purge where practical.

Can dry film lubricant be applied to aluminum?

Yes, but it needs an anodized base first, and NASA JSC PRC-8001 recommends consulting a materials engineer because it is often not the best solution. That document prefers a PTFE impregnated anodic coating for aluminum and, when a dry film is required, specifies Type II or III anodize followed by light glass bead blasting. Bare aluminum gives poor adhesion and galls easily once the film wears through.

What test proves a dry film lubricant lot is acceptable?

Product qualification uses endurance testing such as ASTM D2625. Lot acceptance is usually a tape adhesion test on each part, a solvent wipe for resin bonded films, visual inspection and thickness measurement. PRC-8001 is a good public example: 25 oz/in tape on every part, 50 MEK strokes per lot for resin films, and thickness averaged over at least six readings.

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