When it comes to protecting large metal parts, components, engines, equipment, or industrial machinery from rust and corrosion, VCI (Vapor Corrosion Inhibitor) film is one of the best options available. Unlike traditional methods that rely on messy oils or greases, VCI packaging is clean, dry, and leaves no residue. It works by releasing rust-inhibiting vapors that form a protective shield on metal surfaces—no cleanup required.
To unlock the full rust-prevention power of VCI, metal parts, components, or machinery must be wrapped or enclosed in VCI poly film that is properly sealed. An airtight seal creates the ideal environment for VCI vapors to circulate while blocking out oxygen and moisture—two major causes of corrosion. One of the most effective ways to achieve a tight, secure seal—especially for large or irregularly shaped metal items—is by heat shrinking the VCI film.
When applied and sealed correctly, heat shrinking ensures your VCI film delivers long-lasting protection. Below, we’ll walk through the key dos, don’ts, and best practices for heat shrinking VCI film to keep rust out and protection in.
Steps to Take BEFORE You Heat Shrink
- Clean the Metal Surface: Remove dirt, oil, or moisture using the appropriate cleaning method.
- Pick the Correct VCI Film: Use a VCI film that matches the size, shape, and environment of the metal item. Some films, like ARMOR VCI SEA™ Film, are specifically designed to withstand harsh conditions and outdoor use.
- Ensure the Metal is Cool: Avoid wrapping metal that is still warm from processing because it can cause condensation inside the VCI packaging, which may lead to corrosion.
- Use a Stable Surface: Position the metal item on a platform or pallet for easier wrapping. If possible, elevate it slightly so the film can fully enclose the bottom.
- Pre-Cut the VCI Film: To save time and reduce errors, pre-measure and cut the film to size, ensuring enough overlap for full coverage.
- Wrap the Item Loosely: Position the VCI film around the metal item without stretching and secure it with tape or clamps.
- Protect Sharp Edges: Pad any sharp edges or protrusions to prevent punctures in the film.
- Ventilate the Work Area: Ensure adequate ventilation for heat equipment and fumes.
ARMOR POLY® VCI Film is designed to protect your metal parts with reliable, effective rust prevention.
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The Dos: Best Practices for Heat Shrinking VCI Film
Start at the Corners: Corners of metal parts or equipment are often the trickiest areas to achieve a snug fit. Securing them first helps anchor the film and prevents shifting during the heat shrinking process. Apply heat using a propane-powered or electric heat gun, moving the heat source in a sweeping motion evenly around each corner to avoid wrinkles and ensure the film conforms tightly to the shape of the part for a smooth, secure fit. If needed, gently press the softened film into place by hand (be sure to wear gloves for safety and protection) to help it mold to the proper shape.
Move to the Edges, Then the Center: Once the corners are set, work your way along the edges, applying heat evenly. This pulls the film taut across the surface and removes any slack. After sealing the edges, gradually move toward the center. Distribute heat evenly to eliminate trapped air and reduce the risk of bubbles or uneven shrinking.
Maintain a Safe Distance While Heating: To avoid damaging the VCI film, keep the heat source—whether a heat gun or butane torch—about 6 to 12 inches away. Holding it too close can cause overheating, which may thin or burn through the film, creating holes. Use smooth, sweeping motions to apply heat evenly rather than focusing on one spot.
The Don’ts: What to Avoid When Heat Shrinking VCI Film
Don’t Overheat or Double Shrink: Once the VCI film has been shrunk and hardened, avoid reheating those areas. Double shrinking can make the film brittle and more prone to tearing or punctures. If adjustments are necessary, apply heat only to areas that haven’t fully set.
Don’t Continue Heating If Discoloration Appears: Overheating—seen as scorching, darkening, thinning, or melting—can degrade the film and reduce its corrosion protection. Stop applying heat once the film forms a tight, uniform seal with no signs of discoloration.
Note: When using ARMOR SEA™ Film, which features a black inner layer, the appearance of black spots may indicate that the film has been overheated—burning through up to 70–80% of its thickness and reducing its protective capabilities.
Avoid Wrinkles and Uneven Shrinking: Wrinkles and uneven shrinking can create weak points that allow air or moisture to reach the metal surface. Apply heat evenly and avoid concentrating it in one area to maintain a smooth, consistent seal.
Don’t Rush the Cooling Process: After the metal part is fully wrapped, allow the VCI poly film to cool naturally to set the seal. Rushing the cooling process can weaken the seal and compromise durability. Let the film cool completely to lock in protective performance.
Final Tips for Heat Shrinking Success
Before wrapping up (literally), keep these tips in mind to make your heat-shrinking process safer and more effective:
- Use a propane-powered or electric heat gun when shrinking film on large metal parts or equipment. Propane models are well-suited for outdoor or remote jobs thanks to their portability and high heat, while electric heat guns are a great choice for indoor use where power is easy to access.
- Practice makes perfect: If you’re new to heat-shrinking, start with smaller parts to build skill and confidence.
- Stay safe: Heat guns reach high temperatures. Always follow safety protocols and wear the proper protective gear.
- Make a note of it: Document any special wrapping steps so they can be easily repeated for future shipments or storage.
Heat-shrinking VCI film is an effective solution for protecting large metal parts, equipment, and machinery from rust and corrosion. By following the proper steps, you can create a durable, airtight seal for long-lasting protection during storage or transit. With the right materials and technique, heat-shrinking VCI film provides a simple, cost-effective way to keep your metal parts rust-free, whether in storage or shipping.
Visit ARMOR’s online store for all the rust-prevention packaging materials you need and get them fast with our Stock & Ready™ Program. For expert advice or to learn more, contact an ARMOR Eradicator of Rust today.
