Shrink wrapping a machine, a pump skid, a gearbox or a pallet of spares in a VpCI shrink film is the most reliable way to put steel outdoors for years and get it back without rust. The film does two jobs at once: it is a weather barrier that sheds rain and blocks UV, and it is a source of vapor-phase corrosion inhibitor that conditions the air inside the wrap and protects every metal surface it reaches, including the ones you cannot coat. This guide follows Cortec’s published shrink-wrap application procedure and its Clean-Protect-Preserve program step by step: when to wrap rather than bag, which film to use, how to size it (with a worked example), how to seam and heat-shrink it safely, what to put inside, and how to inspect and eventually unwrap. For film and packaging choices beyond shrink wrap, see the VpCI product selection guide.
When to shrink wrap and when to bag
Cortec’s packaging ladder is organized by two questions: is the equipment going inside or outside, and for how long. Inside, a VpCI-126 bag or film wrap covers 6 months to a year on its own, a year or two with an emitter added, and 3 years or more with a temporary coating under the film. Outside, the answer is always shrink film: VpCI-126 HP UV shrink film or a temporary coating for 6 months to 2 years, and MilCorr shrink film with a coating for 3 years and beyond. In the Product Consultation Guide, MilCorr is the only Cortec packaging film rated 4 (outside, uncovered); every other film, bag and paper is rated 2 (inside storage).
So the decision is simpler than it looks. If the asset will sit outdoors, or in an unheated, open-sided or otherwise weather-exposed building, shrink wrap it. If it is small enough to bag and will stay under a roof, use a VpCI-126 gusseted bag, zip-close bag or a length of VpCI-126 tubing sealed at the ends, and add an emitter for anything over a year. Shrink film also wins indoors when the item is too large or irregular to bag, must be moved by forklift or crane while packaged, or needs a taut package that sheds roof condensation. Packaging-only preservation is, in Cortec’s phrase, “tear off and use,” while coatings add removal time, which is why the sequence below keeps coatings light on spares that will return to service quickly.
Choosing the film
Cortec makes three VpCI shrink films. All three carry the same multi-metal vapor-phase inhibitor; they differ in gauge, UV package and the time they will survive outdoors.
| Film | Gauge | Color | Exposure | Outdoor life | Typical use |
|---|---|---|---|---|---|
| MilCorr VpCI Shrink Film | 10 mil (250 µm) | Opaque buff | Outdoor, uncovered; rated 4 | 5 years or more (Cortec’s published data) | Mothballing, long-term outdoor lay-up, export by deck cargo, military preservation. Also available flame resistant (MilCorr FR, NFPA 701 Test 2). |
| VpCI-126 HP UV Shrink Film | 10 mil | Transparent blue | Outdoor, UV stabilized | Up to 2 years | Outdoor storage where you need to see the equipment through the film; medium-term transit. |
| VpCI-126 Shrink Film | 6 mil | Transparent blue | Indoor, in-crate | Indoor only | Crated exports, indoor storage of large items, over-wrap on pallets. |
Cortec also offers the films with flame-resistant, ESD, UV, opacity and color options on request. MilCorr comes on 20 ft wide rolls in 100 ft and 210 ft lengths, as sheeting or tube; a 210 ft roll weighs roughly 210 lb, so plan a forklift or two people and a dispenser bar. The companion product for every wrap is 3M white shrink tape, 4 in by 108 ft (Cortec’s guide specifies the 3M 4811 preservation tape), which bonds to the film, survives the heat gun and stays put through the storage period.
The opaque buff color of MilCorr is not cosmetic. It is what blocks UV from the film itself and from the equipment under it, and it is the reason MilCorr lasts five years where a clear film lasts two. If you need to inspect during storage, fit a zipper door (below) rather than choosing a clear film for a long outdoor lay-up.
Clean, protect, preserve
Cortec’s Clean-Protect-Preserve program is the sequence the wrap sits at the end of. Skipping the first two steps does not make the film fail; it makes the film protect a part that was already corroding.
Clean
The wrapped surface must be free of dirt, debris, grease and existing corrosion. Degrease with a VpCI-41x cleaner such as VpCI-416, which leaves a flash-rust inhibiting film. Remove rust with VpCI-422 by dip or spray (or the 423 gel on vertical and hard-to-reach areas), keep it wet while it works, then rinse and neutralize with a 10 percent VpCI-414 or 416 solution. Let everything dry; water trapped under film becomes condensation inside it. If you hold a controlled cleaner bath for this work, the concentration testing page gives the refractometer targets.
Protect
For anything staying outdoors more than a year, Cortec’s matrix adds a temporary coating under the film. VpCI-368 (solvent based, waxy, dries in about an hour) suits machined surfaces, shafts, flanges and bare steel that will be handled; VpCI-369 (oil based, never dries, zero VOC) suits internals, ways and anything that benefits from a lubricating film. Both are removed later with VpCI-414 (procedure on the coatings application guides page). Internal void spaces get their own treatment: fog engines, gearboxes, tanks and piping with VpCI-337 at about 1 oz per cubic foot, or dose oil and fuel systems with VpCI-322, VpCI-329 or VpCI-705 (Cortec’s field guidance for pumps and motors is 10 percent by volume of 322 or M-531 in the sump). Cap open pipe and port ends with a VpCI cap or film so the fog stays in. Check additive-to-oil compatibility first on the compatibility charts.
Preserve
This is the wrap itself: emitters placed, film sized and cut, equipment positioned, seams made, film shrunk, openings sealed. The rest of this page covers it in order.
Sizing the film
Measure the equipment’s length, width and height from the farthest point to the farthest point in each direction, including anything that protrudes: handrails, motor housings, lifting lugs, fork pockets. Cortec’s two sizing formulas are:
- Film length = (height × 2) + (width × 2) + overlap
- Film width = height + length + overlap
- Suggested overlap: 12 to 24 inches.
The film length goes up one side, across the top, down the far side and back under, so it carries two heights and two widths plus the seam overlap. The film width runs along the equipment’s length and must also reach up one full height, because the ends are closed by folding the film up and over like a parcel. The equipment sits about four-fifths of the way along the film length, not in the middle, so the single lengthwise seam falls on a side over a support rather than on top where water finds it or underneath where it abrades.
Worked example: a 10 ft × 6 ft × 7 ft machine
Take a machine 10 ft long, 6 ft wide and 7 ft high, and use a 24 in (2 ft) overlap for a long outdoor lay-up.
- Film length = (7 × 2) + (6 × 2) + 2 = 14 + 12 + 2 = 28 ft
- Film width = 7 + 10 + 2 = 19 ft
MilCorr comes 20 ft wide, so the 19 ft film width fits across the roll with a foot to spare and you simply cut 28 ft off the roll. A 20 ft × 100 ft roll yields three such wraps; a 20 ft × 210 ft roll yields seven. If the width formula comes out above 20 ft, wrap in two sheets with a heat-seamed overlap of at least 12 in, or turn the machine so the shorter footprint dimension runs along the film width. Keep the cuts straight and the corners square; a ragged edge is harder to seam.
Before laying out the film, walk the machine for sharp edges and corners and pad them with flame-resistant padding (oil-adsorbent pads work) held with 3M tape, using as little as possible so the inhibitor vapor is not blocked. For voids more than about 3 ft across, run heat-resistant rope every 12 to 24 in in both directions and tie it off so the film does not sag and pool water; do the same across open pipe ends. If the equipment is on a pallet, lay the film across the pallet first so the pallet ends up inside the package.
Wrapping and heat-shrinking, step by step
Tools and PPE from Cortec’s list: tape measure, heat gun or propane shrink gun, flame-resistant insulated gloves and sleeves, safety glasses, steel-toe boots, scissors or box cutter, shrink tape, FR padding, and a ladder or lift for tall units. Check whether your site requires a hot work permit for a propane shrink gun; many do. Clear the work area of dust and dirt so it does not end up inside the wrap, and never walk or drive on the film unless there is no alternative.
- Lay out and position. Roll the film out flat. Place the equipment centered across the film width and roughly four-fifths of the way along the length, leaving enough on the short end to pull up and cover about half the equipment. For a vehicle, drive on slowly. Position the eventual seam over a beam or flat panel.
- Inside seam. Pull the short end up and over the equipment. A little tape can hold it, but use as little as possible: metal under tape is not in contact with the inhibitor vapor.
- Outside layer. Pull the long end completely over to overlap the inside seam. If more than 24 in overlaps, trim, but leave at least 12 in.
- Seam side one. Hold the inside seam down and lift the outside layer to create a pocket between the two. Direct heat into the pocket, keeping the gun at least 6 in from the film until you have a feel for how it reacts; too close burns holes. As soon as the film starts to move and shrink, pat the outer layer down onto the inner with a gloved hand so the two bond. Work along the seam until it is continuous.
- Seam side two (an end). Fold the bottom half of the overhanging film into a triangle on each side, as when wrapping a parcel, and bring it up over the lower half of the end. Seam it. Fold the top half the same way and bring it down over the bottom flap so the top layer fully overlaps the bottom; this is what makes water run off rather than in. Create the pocket, heat, and pat down. Hold the film; do not pull it, because hot film tears.
- Side three has no seam. Leave it for the shrinking pass.
- Seam side four exactly as side two.
- Shrink the film. With all seams made, heat every panel in short, even passes until the film tightens. On large units start at the bottom and work up; angle the heat to drive the film’s movement toward the base. Areas with two or three layers need more heat, and so do areas backed by beams or flat metal. If the equipment is going outdoors, under-shrink, especially on top: UV will keep tightening the film for months and an over-shrunk package can split at the seams.
- Patch any holes. Cut a patch 6 to 12 in larger than the hole on every side, center it, and seam one corner at a time by pocketing and patting, then the edges, then shrink the whole patch lightly. Over-shrinking a patch reopens the hole.
Two safety habits matter most. Keep the flame or hot air moving; a shrink gun held still on 10 mil film burns through in a second or two, and a burn over an oily temporary coating can ignite it, which is why Cortec specifies flame-resistant padding and offers MilCorr FR where the fire code demands it. And treat the film as hot for a minute after each pass: pat, do not grip.
Sealing seams, lift points and anchors with shrink tape
Once the film has cooled, run 3M shrink tape along every heat seam, along the edges of any patch or zipper door, and around any opening. Tape is a second line of defense: the heat seam does the sealing, the tape protects the seam edge from wind lift and UV and gives inspectors a clear visual that the package is intact.
Lift points and anchor points are handled after shrinking, not before. Wrap the unit with the film covering the lugs, shrink it, then cut the smallest opening that exposes each lug, tape the film down to the base of the lug to close the gap, and treat the exposed steel around it with a rust preventative. Cortec suggests BioCorr, VpCI-377 or EcoLine 3220 for this. Cortec’s photographed gear procedure heat-seals the film around lift hooks in the same way, so the crane can pick the package without breaking it.
What goes inside: emitters, desiccant and vents
The film’s own inhibitor conditions the air close to it, but a wrapped machine has cabinets, housings and cavities the vapor reaches slowly. Cortec’s guide calls for emitters in any void larger than 8 cubic feet, spaced evenly if more than one is used. Options: VpCI-101 (1 ft³) and VpCI-111 (11 ft³) devices for control cabinets and housings; BioPad foam emitter pads or the BioPad roll to lay across large flat areas; VpCI-308 powder pouches or EcoPouch (35 ft³ each) for larger enclosed volumes. Emitters and devices are rated 1 (enclosed) in Cortec’s guide, which is exactly the environment a shrink wrap creates.
Desiccant is optional and situational. A VpCI-conditioned package does not need dry air to protect steel, but if the equipment will see large daily temperature swings outdoors, a Desicorr VpCI pouch, which combines desiccant with the inhibitor, limits the condensation that forms each morning. Do not add plain desiccant without inhibitor; once it saturates it stops working and the package has no fallback.
Vents are added where the site or the equipment needs air exchange, for example a diesel unit with a breather that must not be sealed. Make two small cuts in an X no larger than the vent, peel the vent’s adhesive and stick it centered over the cuts. A zipper door lets you inspect without cutting the film: choose a spot over a void rather than where the film is tight against metal, lay the door on the film, heat-seam all four edges exactly as a patch, tape the edges, open the zipper and cut a hole no larger than the door. Every vent and door is a compromise on the inhibitor atmosphere, so fit the fewest you can.
Inspection during storage
Walk the package monthly for the first quarter and then quarterly. Look for tears, wind abrasion at corners and edges, sagging film holding water, seam edges lifting, and tape that has let go. Patch tears immediately using the method above; a small hole in a MilCorr wrap is a five-minute fix and an ignored one is an open door for rain. If a zipper door is fitted, open it briefly, look for condensation or discoloration on exposed steel, and close it. For very long lay-ups Cortec’s fogging guidance is to hang corrosion coupons near an access point, inspect them every one to two years, and re-dose the void with VpCI-337 or fresh emitters if the coupons show attack. Because MilCorr’s inhibitor is in the film itself, the wrap’s protection does not depend on the emitters alone, but the emitters inside cabinets have a finite service life stated on their data sheets and should be replaced at that interval if the storage runs longer.
Unwrapping, return to service and recycling
Cut the film along a side seam with a hooked safety knife, keeping the blade angled away from the equipment, and peel it off. Parts protected by film alone are ready to use immediately; there is no residue to remove, which is the “tear off and use” advantage. If you applied VpCI-368 or 369 under the film, wash it off with a 10 to 20 percent VpCI-414 solution and a hot pressure wash, drain and refill fogged or additive-treated oil systems as your maintenance procedure requires, and remove emitters and desiccant pouches from cabinets. VpCI-126 and MilCorr films are polyethylene and recyclable with LDPE streams; Cortec runs a take-back program for used VpCI film, and one large user’s numbers in Cortec’s training showed the credit and eliminated hauling paying for a baler in the first year. Ask us about the program before you send used film to landfill.
Field results
An offshore rig mothballed in the Gulf of Mexico in 2015 had its hydraulic power unit, heat exchanger, helicopter fuel station, BOP parts, pumps and panels wrapped in MilCorr, with VpCI-126 HP UV used indoors and under cover, emitters and VpCI-308 pouches in panels by volume, and VpCI-391 sprayed over painted equipment and handrails. The rig took a near-direct hit from a hurricane in 2017; at the 2019 inspection every MilCorr wrap was intact and nothing under it had rusted, and the HPU went back to service by cutting the film open. (Cortec Case History #662)
A mobile preservation team serving offshore-equipment repair shops between Houston and New Orleans applies one rule to rebuilt pumps, gearboxes and compressors: VpCI-126 HP UV shrink film if storage will be two years or less or the part is headed offshore, MilCorr if it will sit longer than two years. Inside the wrap they use VpCI-105, VpCI-111 or VpCI-308 pouches by void size, EcoAir VpCI-337 fogged into larger voids, M-531 in gearbox oil, CorShield VpCI-369 on fasteners and ElectriCorr VpCI-239 on electricals. About 60 visits at more than 10 facilities and 70 to 80 parts by mid-2024. (Cortec Case History #837)
Three 158-tonne emergency power cable drums stored indefinitely on the Norwegian North Sea coast were each lifted onto MilCorr, wrapped, fused and heat-shrunk in freezing wind and snow. Seams were shrink-taped, lifting-lug openings taped and custom zipper inspection panels fitted, with netting to follow; re-wrapping is being considered at 5 to 10 years. (Cortec Case History #800)
A UK power station had three multi-million-dollar turbines already rusting under tarps in a planned 2 to 3 year outdoor storage. VpCI-132 foam pads were placed around each turbine and VpCI-126 HP UV film was pulled over and shrunk with a propane gun, replacing the tarps with low-cost outdoor storage for up to 3 years. (Cortec Case History #491)
Frequently asked questions
How long does MilCorr shrink film last outdoors?
Cortec rates MilCorr for outdoor UV exposure of 5 years or more, and it is the only Cortec packaging film rated for uncovered outdoor storage in the Product Consultation Guide. VpCI-126 HP UV shrink film is rated for up to 2 years outdoors; standard 6 mil VpCI-126 shrink film is for indoor use.
Can I use a regular heat gun instead of a propane shrink gun?
Yes for small packages and for seams. A propane shrink gun is faster on 10 mil film over a large machine. Either way, start at 6 in or more from the film, keep it moving, and wear FR gloves and sleeves. Check whether your site treats a propane gun as hot work.
Do I need a coating under the film?
Cortec’s matrix adds a temporary coating for outdoor storage of 3 years or more and for indoor storage of 3 years or more; for shorter periods the film, with emitters in enclosed voids, is sufficient. Coatings add removal time on return to service, so use them where the storage length justifies it.
How do I calculate the film size?
Film length = 2 × height + 2 × width + overlap; film width = height + length + overlap; overlap 12 to 24 in. For a 10 ft × 6 ft × 7 ft machine with a 2 ft overlap that is 28 ft × 19 ft, which fits across a 20 ft MilCorr roll.
Why does Cortec say to under-shrink for outdoor storage?
Sunlight continues to shrink the film for months after installation. A package shrunk fully tight indoors and then placed outdoors can split at the seams or corners as it keeps tightening. Leave it slightly less taut, especially on top.
Will the film protect copper, aluminum and electronics as well as steel?
MilCorr and VpCI-126 carry a multi-metal inhibitor and are rated for carbon steel, stainless, cast iron, aluminum, galvanized, copper, brass and solder. Add VpCI-101 or 111 emitters inside control cabinets so the vapor concentration there matches the rest of the package.
Can I inspect the equipment without cutting the wrap?
Fit a zipper door when you wrap, over a void space rather than where the film touches metal, and seam and tape it as described above. Otherwise, cut a small inspection hole and patch it with a piece of film 6 to 12 in larger than the hole.
Planning a lay-up, an export shipment or a mothballing project? Tell us the equipment dimensions, where it is going and for how long, and we will spec the film, tape, emitters and coatings as a single package. Contact Solvent Recycling Systems. Related guides: Cortec coatings application guides, VpCI concentration testing, compatibility charts, and the full Cortec product category.
Data source: compiled from Cortec application guides and technical literature (Cortec shrink-wrap application guide, Clean-Protect-Preserve field procedure, films training material and the Cortec product brochure, 2013–2017 vintage); confirm against the current product data sheet before specifying.
