An aircraft that sits is an aircraft that corrodes. Cortec publishes a zone-by-zone layup procedure for modern aircraft that uses its VpCI® vapor phase corrosion inhibitors to protect the airframe, engines, fuel and hydraulic systems, avionics and landing gear while the aircraft is parked for months or years. This page restates that procedure as a working checklist for base maintenance crews, MRO shops, fleet operators and private owners, with Cortec’s published dose for each step and a link to the Solvent Recycling Systems listing where we stock the product. Where a step calls for a product we do not carry as a stock item, it is marked “available to order” and we quote it on request. For the general logic of choosing a VpCI product for a metal and an environment, start with the VpCI product selection guide; for ships, tugs and workboats, see the companion vessel layup and long-term storage procedure.
Why aircraft corrode in storage
Cortec’s own summary of the problem is short: moist, salt-laden air and fluctuating humidity condense on electrical systems, rotating equipment, hydraulics, bolts, valves and motors, and the result is premature failure, unplanned repair cost and delay when the aircraft is needed again. In the upper Midwest the humidity swing is the main enemy. A hangar or ramp that goes from 20 degrees F overnight to 50 degrees F by noon in March pulls condensation onto every cold metal surface inside the aircraft, including the ones no inspection panel reaches: engine flow paths, fuel tank bays, hydraulic reservoirs, avionics racks, wheel wells and control-surface hinges. Salt from de-icing chemicals and coastal air makes the condensate conductive, and the mixed metals in an airframe (aluminum alloys, steel fasteners, cadmium plating, magnesium castings, copper wiring) form galvanic couples the moment an electrolyte bridges them.
Conventional preservation answers each of those spaces separately: oil in the engine, desiccant in the cabin, grease on the gear, nitrogen in whatever can be sealed. Cortec’s approach is to use the same family of chemistry in every zone. VpCI molecules vaporize from a source (a pouch, an emitter, a fogged liquid, a treated oil), diffuse through the enclosed air and condense as a molecular layer on every metal surface they reach, including recesses and threads. When a door is opened or a surface is wiped, the layer re-forms as long as the source is present and the space is closed again. That is why the procedure below leans on pouches, emitters and fogging for the interior volumes and on contact products (coatings, greases, oil and fuel additives) only where a surface is exposed to weather or immersed in a fluid.
Before you start: clean, then protect
Every zone in Cortec’s procedure begins with a clean surface. Dust, hydraulic fluid, exhaust soot and old preservative all block the inhibitor from reaching the metal. The first step of the published procedure is a full exterior wash with VpCI-415, a biodegradable aircraft cleaner that conforms to Boeing D6-17487 Rev P and is listed on the Qualified Products List for MIL-PRF-87937D Type IV. Cortec’s data sheet gives dilutions of 5 percent for light cleaning, 10 percent for medium and 20 percent for heavy soil; the ship layup chart standardizes on 10 percent by volume. VpCI-415 leaves a light flash-rust inhibitor on the washed surface, so the aircraft is protected between the wash and the next step. Loose parts, ground equipment and removed components that are rusty go through a rust remover first (VpCI-422 for ferrous parts; use VpCI-426 or VpCI-429 where aluminum is present) and then a VpCI-415 or VpCI-414 rinse. If you run a parts washer for that work, the clean-then-protect article covers the dip-and-dry sequence.
The procedure zone by zone
The order below follows Cortec’s published procedure. Doses are Cortec’s figures; where the current product data sheet gives a different or wider range, the note says so. Confirm every dose against the data sheet shipped with the product before treating a certificated aircraft, and check the airframe and engine manufacturer’s storage instructions, because the OEM procedure governs.
Zone 1: Engines and nacelles
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Fog the engine flow path (inlet through exhaust) with a waterborne VpCI | VpCI-337 | 0.5 oz per cubic foot of enclosed volume (the data sheet range is 0.5 to 1.0 oz/ft³); seal openings after fogging | VpCI-337, 5 gallon pail; for small engines and short jobs, the EcoAir 337 aerosol fogger |
| Place a VpCI pouch at the air inlet behind the inlet cover | VpCI-308 pouch | One pouch per 35 ft³ of enclosed volume | VpCI-308 pouches |
| Spray external linkages, cables and control rods | VpCI Super Penetrant | Light spray on every joint and pivot | Available to order; EcoLine ELP is the stocked biobased penetrant and lubricant |
| Shrink wrap the engine or nacelle for outdoor storage | VpCI-126 HP UV shrink film | Wrap and heat-shrink; overlap seams as a watershed | Available to order; MilCorr VpCI shrink film is the stocked outdoor film, and the shrink-wrap guide covers sizing and seaming |
| Add a VpCI to the engine oil (piston engines and gearboxes) | M-531 or VpCI-326 / VpCI-329 | M-531 at 5 percent in gearbox oil per Cortec’s procedure; VpCI-326 and 329 are used at 1:10 in the field notes below | M-531, VpCI-326, VpCI-329 |
Cortec’s procedure treats the flow path with a fogged liquid and the inlet plenum with a pouch. The fog deposits inhibitor on the compressor and turbine blading immediately; the pouch keeps the air inside the covered inlet saturated for the rest of the layup. VpCI-337 is water-based and Cortec says equipment treated with it can usually be commissioned without removal. For an engine that will be stored off-wing, Cortec Case History #748 (below) describes a bag-and-pouch method that avoids oil on bare metal entirely.
Zone 2: Fuel system
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Fog the jet fuel system (Jet A / Jet A-1) and tanks | VpCI-707 | 1 oz per cubic foot of tank volume per Cortec’s aircraft procedure; 0.2 percent by volume when added to fuel per Cortec’s ship layup chart | Available to order (jet-fuel grade) |
| Treat gasoline or diesel in piston aircraft and ground support equipment | VpCI-705 | 0.1 to 0.15 percent of tank volume in wet tanks; 1.5 oz per 10 gallons of tank volume fogged into a dry tank | VpCI-705 |
VpCI-707 is the product Cortec names for turbine fuel. VpCI-705, which we stock, is the general fuel additive for gasoline and diesel and is the one Cortec used on the USAF vehicle fleet in Case History #557. It protects the liquid, the fuel-air interface and the vapor space above the fuel, and it has been evaluated against the MIL-PRF-25017F rust-prevention test. For fuel tanks that are drained rather than kept wet, Cortec’s data sheet gives the dry-tank fogging dose above. Do not put VpCI-705 in a turbine-fuel system without checking with Cortec technical service; ask us to quote VpCI-707 instead.
Zone 3: Hydraulics
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Add a VpCI to the hydraulic reservoir and cycle the system | M-531 (mineral and synthetic hydrocarbon fluids) or M-528 (water-soluble PAG fluids) | 2 percent per Cortec’s aircraft procedure; the M-531 data sheet gives a typical range of 3 to 5 percent in the base stock | M-531; M-528 available to order |
| Coat exposed actuator rods and cylinders | VpCI-369 D | Spray a thin film; dries to a soft, oily film that lubricates as well as protects | VpCI-369 D or the CorShield 369 aerosol |
Aircraft hydraulic fluids are phosphate esters or synthetic hydrocarbons, and the M-531 data sheet says solubility should be verified in the base oil you use. Check the elastomer and additive tables on the Cortec compatibility charts page and run a bench compatibility test on a sample before dosing a reservoir. After the additive is in, cycle the actuators so the treated fluid reaches every cylinder, then leave the system full.
Zone 4: Cockpit and avionics
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Clean and spray connectors, contacts, relays and terminal strips | ElectriCorr VpCI-239 | Very light mist; dries in 1 to 2 hours at 70 degrees F. A heavy mist sags and stays wet. | VpCI-239 aerosol or bulk pail; for indoor racks the VpCI-238 cleaner |
| Install an emitter in every closed avionics bay, rack, junction box and instrument panel | VpCI-101, VpCI-105, VpCI-111 | One VpCI-101 per 1 ft³, one VpCI-105 per 5 ft³, one VpCI-111 per 11 ft³ (Cortec’s layup chart rounds to 10). Rated for up to 24 months in a closed enclosure. | VpCI-101, VpCI-111; VpCI-105 available to order |
| Larger electronics compartments and the cockpit itself | VpCI-308 pouch | One pouch per 35 ft³ | VpCI-308 pouches |
The emitters are the reason this procedure works on avionics. They add nothing to the surface that has to be cleaned off later, they do not affect electrical, optical or mechanical performance, and VpCI-111 is accepted for U.S. military and NATO use. Peel the adhesive back, press the emitter onto a clean spot inside the enclosure, write the date on the label and close the door. If the bay is opened often during the layup, or the enclosure is not tight, Cortec’s guidance is to replace the emitter sooner than the 24-month rating.
Zone 5: Cabin, galley, lavatories and baggage holds
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Space VpCI pouches along the cabin aisle, cockpit, galley, lavatories and baggage compartments | VpCI-308 pouch | One pouch per 35 ft³ of interior volume, evenly spaced | VpCI-308 pouches |
| Control humidity in a sealed cabin that will not be entered | Desicorr VpCI | Combination desiccant and VpCI pouch; one 1-unit pouch per 5 ft³ | Desicorr NW VpCI |
| Treat toilets and holding tanks | ECO-SEPT (toilets), PORTA-TREAT (holding tanks) | Additive per label | Available to order |
To size the pouch count, take the cabin length times width times height in feet, subtract nothing for seats and galleys (they take up volume but they also hide metal that needs protection), and divide by 35. Round up. A pouch inside a Tyvek envelope releases inhibitor through the membrane and does not shed powder, so nothing has to be vacuumed out at recommissioning; you collect the pouches and dispose of them.
Zone 6: Landing gear, wheels and brakes
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Spray gear joints, torque links, uplocks and pivots | VpCI-369 D | Thin oily film; ready to use, do not dilute | VpCI-369 D |
| Coat exposed bare-metal gear surfaces and wheel hubs | VpCI-368 D | Spray or brush; dries to a waxy film rated by Cortec for up to 2 years outdoors; removable with an alkaline cleaner or solvent | VpCI-368 D; for MIL-PRF-16173E Grade 1 work, VpCI-368 M |
| Grease every zerk fitting and wheel bearing | CorrLube VpCI Lithium EP Grease | Standard grease-gun application until clean grease shows | CorrLube pail or cartridges |
| Treat tires and rubber seals against ozone cracking | EcoLine Biobased Rubber Revitalizer | Wipe or spray on tire sidewalls, seals and hoses | Available to order; Rawn Re-Grip is the stocked soy-based rubber cleaner and protectant |
Zone 7: Exterior, control surfaces and openings
| Step | Product | Dose or method | SRS listing |
|---|---|---|---|
| Wash the whole exterior | VpCI-415 | 10 percent by volume (5 to 20 percent by soil load); pressure wash or foam and rinse | VpCI-415 |
| Spray every hinge and joint on ailerons, flaps, slats, stabilizers, rudder, doors and access panels | VpCI-369 D | Thin film into the joint; wipe the overspray off painted skin | VpCI-369 D or CorShield 369 aerosol |
| Cover inlets, exhausts, pitot and static ports, vents and drains | VpCI-126 Blue film and tape | Bag or wrap the opening and tape it closed after the pouch or fog is in place | VpCI-126 Blue tubing, zip-close bags |
| Protect a clear-coated or bare aluminum surface that will stay outdoors | VpCI-391 | Clear, non-tacky water-based temporary coating; removable with VpCI-414 | VpCI-391 |
| Shroud an aircraft parked outside long term | MilCorr VpCI shrink film | 10 mil UV-stabilized film over a frame; the only Cortec packaging film rated for uncovered outdoor storage | MilCorr 20 x 210, MilCorr 20 x 100, shrink tape |
Recommissioning the aircraft
One of the arguments for this procedure over oil-and-grease preservation is how little there is to undo. Work the zones in reverse.
- Emitters, pouches and desiccant. Open each bay, remove the devices, and note the date on each label against your layup log. Nothing is left behind on the surfaces.
- Fogged spaces. VpCI-337 in the engine flow path does not normally need removal before commissioning; Cortec’s guidance is to review the application with its technical service before starting a turbine. Uncover the inlet and exhaust and run the normal pre-start checks.
- Fuel and oil additives. VpCI-705 and VpCI-707 stay in the fuel and burn with it. M-531, VpCI-326 and VpCI-329 stay in the oil until the next scheduled change; they are lubricant additives, not contaminants.
- VpCI-369 D on joints and hinges. Leave it. It is a lubricating film and continues to protect in service. Wipe any overspray off paint with a rag.
- VpCI-368 D and VpCI-391 on exposed surfaces. Remove with VpCI-414 at the dilution on its data sheet, or with mineral spirits for the waxy 368 film. Removal steps and dwell times for every temporary coating are on the coatings application guides page.
- Grease. CorrLube is a service grease; purge on the normal schedule.
- Shrink film. Cut the film away from the frame, fold it and dispose of it as polyethylene. Cortec’s data says the object is ready for use on removal.
Shopping list
Everything on this page in one table. Products without a stocked listing are quoted on request.
| Product | Used in | Listing |
|---|---|---|
| VpCI-415 aircraft cleaner | Exterior wash, parts cleaning | 5 gallon, 55 gallon |
| VpCI-308 pouch | Cabin, engine inlet, large bays | 50 per drum |
| VpCI-337 fogging fluid | Engine flow path | 5 gallon, 55 gallon, EcoAir 337 aerosol |
| M-531 oil additive | Hydraulics, gearboxes, engine oil | 5 gallon, 55 gallon |
| VpCI-326 / VpCI-329 oil additives | Piston engine and gearbox pickling | VpCI-326, VpCI-329 |
| VpCI-705 fuel additive | Gasoline and diesel tanks | 5 gallon |
| VpCI-707 jet fuel additive | Turbine fuel systems | Available to order |
| ElectriCorr VpCI-239 | Contacts, connectors, avionics | aerosol 6-pack, 5 gallon |
| VpCI-101 / VpCI-111 emitters | Avionics bays, junction boxes | VpCI-101, VpCI-111; VpCI-105 available to order |
| Desicorr NW VpCI | Sealed cabin, engine bags | 1 unit, 1/6 unit |
| VpCI-369 D | Gear joints, control-surface hinges, actuator rods | 5 gallon, CorShield 369 aerosol |
| VpCI-368 D / VpCI-368 M | Exposed gear and bare-metal surfaces | VpCI-368 D, VpCI-368 M, CorShield 368 aerosol |
| VpCI-391 | Clear coating for exposed aluminum | 5 gallon |
| CorrLube VpCI Lithium EP Grease | Zerk fittings, wheel bearings | 5 gallon, cartridges |
| VpCI Super Penetrant | Engine linkages, seized fasteners | Available to order (EcoLine ELP stocked) |
| VpCI-126 Blue film and bags | Openings, removed components, engine bags | tubing, zip bags, gusseted bags |
| MilCorr VpCI shrink film | Outdoor shrouding | 20 x 210, 20 x 100 |
| VpCI-414 remover | Coating removal at recommissioning | 5 gallon |
| Rubber revitalizer, ECO-SEPT, PORTA-TREAT, M-528, VpCI-126 HP UV shrink film | Tires, waste systems, PAG hydraulics, engine wrap | Available to order |
Federal, USAF and MRO quoting
Much of this procedure maps directly onto military and federal specifications, which matters when the buyer is a base supply office or a prime contractor working to a preservation spec. From Cortec’s published qualification data: VpCI-368 M is on the DLA Qualified Products List for MIL-PRF-16173E Grade 1 with NSN 8030-00-062-6950 and three further NSNs; VpCI-415 carries NSN 6850-01-583-3039 under MIL-PRF-87937D Type IV and conforms to Boeing D6-17487 Rev P; VpCI-101 carries NSN 6850-01-338-1392, VpCI-105 NSN 6850-01-406-2060 and VpCI-111 NSN 6850-01-408-9025; VpCI-126 Blue film has been evaluated to MIL-PRF-22019D and MIL-PRF-3420G, and VpCI-146 paper to MIL-PRF-3420. Cortec has also published a deep-storage cost-savings study for USAF vehicles and equipment and presented the same method to NATO. Solvent Recycling Systems quotes these products by NSN and by tail count; send us the fleet size, the storage location and the planned duration and we will size the pouches, emitters, fogging fluid and additives for you.
Field notes from Cortec case histories
The following are drawn from Cortec’s published case history library and retold in our words. Customer names are omitted.
- Cortec Case History #557. A U.S. Air Force base in the Pacific parked roughly twenty million dollars of airfield damage-repair vehicles in an open field at one of the service’s most corrosive sites. The program used a VpCI-415 pressure wash, VpCI-369 D on hinges, pintles and cylinders, VpCI-239 on all electricals, VpCI-105 and VpCI-111 emitters in fuse boxes, tool boxes and cabs, CorrLube on zerks, VpCI-391 in engine compartments, VpCI-705 in the fuel, a peelable coating on truck beds and blades, and a matte VpCI-386 topcoat over the paint. Crews expected large repair-labor savings and other bases in the region asked to copy the program. It is the closest published analogue to a whole-fleet aircraft layup, and every product except the peelable coating is in the tables above.
- Cortec Case History #748. An engine builder in the northeastern United States was seeing corrosion and staining on the exterior of aircraft engines in storage and shipping. The fix was a large VpCI-126 gusseted bag over the pallet frame, the engine hoisted in, Desicorr NW pouches inside, and for humid or hot destinations a three-second burst of VpCI-337 aerosol before sealing. Staining stopped, oil on bare metal was eliminated, and customers received clean engines.
- Cortec Case History #254. A private pilot in Wisconsin winterized the 180 hp engine on a restored 1965 amphibian following the engine maker’s service letter: 26 oz of VpCI-326 in 8 quarts of oil (1:10), a brief run, shutdown, and extra mix sprayed into the cylinders after five months. Cortec describes this as a recognized OEM-approved storage procedure.
- Cortec Case History #234. A private aircraft owner in Minnesota stored an overhauled engine in a garage through a decade of winters because the OEM-listed preservation materials were unobtainable. VpCI-329 was poured into the engine interior, the engine wrapped in Cor-Pak VpCI stretch film and crated with silica-gel bags and desiccant spark-plug plugs. It was unwrapped nearly ten years later with no exterior corrosion.
- Cortec Case History #323. An Air Force base in Ohio converting to environmentally preferred products used VpCI-111 emitters and ElectriCorr 238 on electrical equipment, MilCorr shrink film for long-term storage, and VpCI-414 with Corwipe for stored tools.
- Cortec Case History #692. An aviation MRO in the tropics whose desiccants kept failing in non-air-conditioned warehouses switched its spares storage to EcoPouch VpCI pouches plus Cor-Pak VpCI stretch film.
Frequently asked questions
How long will the VpCI layup protect a parked aircraft?
Cortec’s published aircraft procedure does not state a duration. The component data sheets do: VpCI-101, 105, 111 emitters and VpCI-308 pouches are rated for up to 24 months in a closed enclosure, VpCI-368 D for up to 2 years outdoors, and MilCorr shrink film for multi-year outdoor exposure. Plan on a 24-month cycle for replacing emitters and pouches, sooner if bays are opened often, and inspect at six-month intervals.
Does the procedure control humidity, or do I still need desiccant?
VpCI does not dry the air; it protects the metal in spite of the moisture. In a cabin or bag that will be sealed and left, the combination pouch Desicorr NW VpCI gives both. In bays that are opened for inspection, desiccant saturates quickly and VpCI is the part that keeps working.
Nitrogen blanketing or VpCI fogging for the engine and fuel system?
Nitrogen only works while the seal holds; open an inspection cover and the protection is gone until the purge is repeated. VpCI-337 deposits an inhibitor layer on the metal, so the protection survives an opened cover and re-forms when it is closed. Cortec has published comparisons of VpCI-337 against nitrogen and dry-air blanketing, and its refinery case history (#519) describes a job where a nitrogen purge failed early and VpCI fogging replaced it.
What is the engine oil additive dose?
Cortec’s aircraft procedure gives M-531 at 5 percent in gearbox oil and 2 percent in hydraulic fluid. The M-531 data sheet gives a typical range of 3 to 5 percent in the base stock. The two piston-engine case histories used VpCI-326 or VpCI-329 at 1:10 in engine oil. Follow the engine manufacturer’s service letter where one exists and confirm compatibility on the compatibility charts.
Is it safe on avionics?
The emitters and VpCI-239 are designed for electronics. Cortec’s data sheets say the emitters do not interfere with electrical, optical or mechanical performance, VpCI-111 is accepted for U.S. military and NATO use, and VpCI-239 can be used in contact with engineering plastics and elastomers. Use a very light mist of 239; a heavy coat sags and stays wet.
What has to be removed before the aircraft flies again?
Pouches, emitters, desiccant, covers and shrink film come out or off. VpCI-368 D and VpCI-391 coatings are washed off with VpCI-414. Oil and fuel additives, VpCI-369 D on joints and CorrLube grease stay in service. VpCI-337 in a fogged space normally does not need removal, subject to a review with Cortec technical service for turbine flow paths.
Can I check that a diluted VpCI-415 or VpCI-337 bath is at the right strength?
Yes, with a refractometer. The Brix-to-concentration formulas and target readings for Cortec’s water-based products are on the VpCI concentration testing page.
Does the same procedure apply to boats and ships?
Largely yes, with different zones (cooling water, ballast, boilers, deck machinery). The vessel layup and long-term storage page covers Cortec’s ship procedure and its marine OEM approvals.
Solvent Recycling Systems is an authorized Cortec® distributor serving Illinois, Wisconsin, Indiana, Michigan and federal customers nationwide. See the full Cortec VpCI line, browse the VpCI product selection guide, or contact us with your fleet size and storage plan for a sized quote.
Data source: compiled from Cortec’s published aircraft long-term storage procedure, current product data sheets and Cortec case histories; confirm every dose against the current product data sheet and the airframe or engine manufacturer’s storage instructions before specifying.
