The solvents at a glance
Where to buy| Solvent | Flash point (NIOSH) | Typical use | Watch for |
|---|---|---|---|
| MEK | 16 F (-9 C) | Coating wipe test, thinning, cleaning | Not on nitrocellulose; not in confined spaces (AC 6-90a(14)) |
| Isopropyl alcohol | 53 F (12 C) | Final wipe before paint, light cleaning | Light cleaner only |
| Acetone | 0 F (-18 C) | Degreasing, resin thinning | Attacks plastics and finishes; fire risk with conversion coat |
| Dry cleaning solvent | See SDS | Clean reworked area before conversion coat | Never kerosene or fuel (AC 6-136h) |
Flash points: CDC NIOSH Pocket Guide, Fahrenheit as published; Celsius converted. Always the SDS of your product first.
MEK (methyl ethyl ketone, 2-butanone)
What it is. A highly flammable, fast-evaporating ketone solvent (FAA-H-8083-31B ch. 8).
What it is for. Paint and primer thinning and removal, removing decals and residue, cleaning before bonding or painting, and the wipe test that identifies a coating: acrylic lifts pigment onto the rag, epoxy does not (Handbook ch. 8).
How it is used. Wipe, do not rub, and use clean cloths. The Handbook says not to use MEK on nitrocellulose finishes. Check the cleaner against the SRM and the paint maker before it touches a finish you did not apply.
Life and cure. Not a curing product. Evaporates quickly, so wipe off before it dries and re-wipe with a clean cloth.
Safety. NIOSH lists a flash point of 16 F (about -9 C), flammable liquid class IB, and exposure limits of 200 ppm (8 hour average, NIOSH REL and OSHA PEL). AC 43.13-1B par. 6-90a(14) says not to use low flash point solvents such as MEK and acetone in confined locations. The Handbook advises protective gloves. Follow the SDS.
Specification. Shop solvent grades are set by the SRM or paint maker; this page gives no grade.
Equivalents. Acetone and isopropyl alcohol are different solvents with different effects, not equivalents. A swap needs approved data.
Isopropyl alcohol (isopropanol, IPA)
What it is. A flammable alcohol solvent, also called rubbing alcohol (Handbook ch. 8).
What it is for. Wiping fingerprints and hand oil before painting, removing marker and grease pencil, and as a non-chlorinated cleaner for parts such as titanium weld joints (denatured isopropyl is named in the Handbook).
How it is used. Wipe with a clean cloth and dry with another before it evaporates. It is a light cleaner: heavy grease and sealant need a stronger solvent or a remover.
Life and cure. No cure. Evaporates fast.
Safety. NIOSH lists a flash point of 53 F (about 12 C), class IB flammable liquid, and 400 ppm (8 hour average, NIOSH REL and OSHA PEL). Follow the SDS.
Specification. Often called for by name in manuals as a final wipe; the SRM gives the grade. Federal spec TT-I-735 is named in AC 43.13-1B par. 6-221 for a water-immersion wash mix.
Equivalents. Denatured ethanol is a cleaner and degreaser before painting (Handbook ch. 8); it is a different product. Do not swap without approved data.
Acetone
What it is. A fast-evaporating, colourless solvent and strong degreaser (Handbook ch. 8).
What it is for. Metal preparation and removing grease; thinning resin, vinyl and adhesives; a superglue remover. The Handbook says not to use it as a dope thinner.
How it is used. Wipe small areas and dry at once. It attacks many plastics, paints and sealants: keep it off anything the SRM does not clear.
Life and cure. No cure. Evaporates fastest of the three.
Safety. NIOSH lists a flash point of 0 F (about -18 C), class IB flammable liquid, NIOSH REL 250 ppm (8 hour average) and OSHA PEL 1000 ppm. AC 43.13-1B par. 6-90a(14) bars it from confined locations, and par. 6-136 warns that conversion-coat solutions must not contact acetone: fire may result. Follow the SDS.
Specification. No aerospace grade is stated in the sources; the SRM or process spec sets it.
Equivalents. MEK is a stronger, slower solvent; neither replaces the other on a finish.
1,1,1-Trichloroethane (historic)
What it is. A chlorinated solvent that was a standard shop degreaser and vapour-degreasing solvent.
What it is for. Historic only. Older manuals and old procedures name it.
How it is used. Do not look for it. Where an old document names it, use the substitute the current manual names.
Life and cure. Not applicable.
Safety. Production was phased out under the Montreal Protocol and the US Clean Air Act (class I ozone-depleting substance); consumption ended by 1 January 1996 in developed countries (Environment Canada). Not a shop product today.
Specification. Old military and company specifications; replaced in current manuals.
Equivalents. Whatever the current SRM or process specification calls out; this page names none.
Dry cleaning solvent
What it is. The petroleum-type solvent AC 43.13-1B names for cleaning a reworked area. The AC does not give a specification at that point.
What it is for. Cleaning an area after blend-out of corrosion, before the conversion coat (par. 6-136h).
How it is used. The AC says not to use kerosene or any petroleum fuel in its place (par. 6-136h; again in 6-136j for magnesium).
Life and cure. No cure.
Safety. Flammable. Follow the SDS and AC 43.13-1B par. 6-90.
Specification. Not given in the AC text we read.
Equivalents. Not kerosene or fuels. Anything else needs the SRM.
Skydrol-safe cleaners
What it is. Cleaners sold as safe where phosphate-ester hydraulic fluid (Skydrol, Hyjet) is or may be present. AC 43.13-1B ch. 9 describes the fluid itself.
What it is for. Cleaning near hydraulic components, wheel wells and flap tracks, and on finishes that must resist the fluid. A related feature is a fluid-resistant primer: PPG says CA7233 has a high degree of Skydrol resistance.
How it is used. Use the cleaner the AMM names for the area. We found no public standard that defines a Skydrol-safe cleaner, so the label is a maker's claim to check against the manual.
Life and cure. No cure.
Safety. Follow the cleaner's SDS and the AMM. Phosphate-ester fluid handling is covered in AC 43.13-1B ch. 9.
Specification. Set by the aircraft maker or the cleaner's own approvals; none stated in the sources.
Equivalents. Not interchangeable by name. Match the approval in the AMM.
Questions people actually ask
Can I use acetone instead of MEK?
They are different solvents. The Handbook describes both, and the SRM or the paint maker names the one for a task. Do not swap them on a finish without approved data.
Why is trichloroethane in old manuals?
It was a standard degreaser until the Montreal Protocol and the Clean Air Act ended its production in the 1990s. Use the current manual's substitute.
Is kerosene a cleaning solvent?
AC 43.13-1B says no: do not use kerosene or any petroleum base fuel as a cleaning solvent (par. 6-136h).
What does a Skydrol-safe cleaner mean?
That the maker claims it does not attack phosphate-ester fluid residue or fluid-resistant finishes. No public standard defines it; the AMM decides.
Limits — when NOT to use this
What the sources support, and no further.
- No procedures. The SRM and AMM name the cleaner for each task.
- No grade numbers. The sources do not give solvent specification numbers for shop use.
- Flash points are NIOSH values in US units; the SDS of your product may differ.
- Skydrol-safe is a label, not a standard; we found none to cite.
Where to buy
Distributors coming soon.
Sources
- FAA AC 43.13-1B CHG 1, Chapter 6 (corrosion control, safety precautions, finishes) — Pars. 6-90 (safety precautions), 6-134 to 6-136 (finish, conversion coat, 48 hour rule, fasteners), section 4 (corrosion preventive maintenance, MIL-C-16173 Grade 4); par. 5-63 (cleaner types).
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook - Airframe, Volume 1 — Chapter 8, aircraft finishes: finishing materials (acetone, alcohol, MEK) and the solvent test for coatings; chapter 7, sealing of bolted composite repairs.
- CDC NIOSH Pocket Guide to Chemical Hazards: 2-Butanone (MEK) — Flash point, exposure limits and flammability class.
- CDC NIOSH Pocket Guide to Chemical Hazards: Acetone — Flash point, exposure limits and flammability class.
- CDC NIOSH Pocket Guide to Chemical Hazards: Isopropyl alcohol — Flash point, exposure limits and flammability class.
- Environment and Climate Change Canada: 1,1,1-Trichloroethane — Montreal Protocol phase-out of methyl chloroform (consumption ended by 1 January 1996 in developed countries).
- US Clean Air Act, section 604 (archived EPA text) — Phase-out schedule for class I ozone-depleting substances, including methyl chloroform.
- PPG Aerospace, Desoprime HS CA7233 Military Epoxy Primer, Technical Data Sheet — MIL-PRF-23377 Type I Class C2, mix ratio, induction, pot life, film thickness, dry times, VOC, flash point, shelf life.