VCI corrosion protection: How does it work and when is it worthwhile?

How does the VCI principle work inside closed packaging?

The abbreviation VCI stands for Volatile Corrosion Inhibitor [1], [5]. These corrosion-inhibiting substances are homogeneously compounded into the LDPE or LLDPE carrier film during extrusion [2], [6]. As soon as a metallic workpiece is placed inside a VCI bag or wrapped in VCI film and the package is closed, the film walls continuously release minute amounts of the active agent into the gas phase of the interior space [1], [4].

Through diffusion, the gaseous inhibitors distribute evenly throughout the entire cavity – reaching bores, threads, crevices and recessed internal geometries – and condense as an invisible molecular protective film on the metal surface [1], [5]. This layer prevents electrochemical corrosion reactions caused by humidity, condensation and oxygen [4], [5]. At the same time, the polyethylene film acts as an external barrier against moisture and dirt [2].

When is VCI worthwhile compared with traditional oil or wax preservation?

In conventional corrosion protection, machined steel, cast-iron or transmission components are coated with corrosion-protection oils, greases or waxes before shipment [1]. This requires a dedicated application step at the sender's plant and time-consuming washing or solvent degreasing at the recipient's facility before the parts can enter assembly, painting or finishing [1], [5].

With VCI corrosion protection film, both steps are eliminated: the packaging provides mechanical transport protection and active preservation simultaneously [1], [2]. The method is particularly economical for ready-to-install automotive components, stamped and turned parts, bearings, tools and complete machinery in overseas and container export where strong temperature fluctuations and condensation occur [2], [3], [6].

Criterion	Traditional oil / grease preservation	VCI corrosion protection film (PE)
Application prior to shipping	Manual or automated oiling/dipping required [1]	Place in VCI bag or wrap in VCI film [1], [3]
Reach into internal cavities	Recessed cavities often incompletely wetted [1]	Gas phase reaches bores, threads and narrow gaps [1], [5]
Cleaning by the recipient	Degreasing/washing and disposal of cleaning media required [1]	No cleaning needed; active agent evaporates without residue [1], [2]
Visual and customs inspection	Surface obscured by oil/wax film	Possible through transparent film without opening package [2], [6]
Packaging disposal	Oil-contaminated packaging difficult to recycle	Mono-material PE film is 100% recyclable [6]

Which delivery formats are used for which components?

Depending on part size, geometry and the packing workflow in production or dispatch, different converted formats are used [3], [6]:

• VCI flat bags: For small parts, bolts, turned parts, stampings and individual spare parts packed and heat-sealed manually or semi-automatically [3], [6].
• VCI side-gusseted bags and sacks: For larger, angular or bulky assemblies as well as tailored liners (inliners) for small load carriers (KLT), cartons and mesh pallet boxes [3], [6].
• VCI pallet hoods: For covering complete pallet loads, engines, control cabinets or machinery on export pallets [3], [6].
• VCI tubular film and flat film on rolls: For long goods such as shafts, pipes and profiles, and for flexible cutting-to-length and wrapping at packing stations or automated lines [2], [6].
• Cut-to-size sheets: As interleaves in containers or custom sheets made to drawing [6].

Metal compatibility: Steel, cast iron and multi-metal applications

When specifying a VCI film, the metal to be protected must always be taken into account, because no single universal active agent protects all metals identically [2]. For purely ferrous materials (unalloyed steel, grey cast iron, ductile iron), classic ferrous formulations are used [2], [6]. If an assembly combines different metals – such as steel together with aluminium, galvanised steel, copper, brass or bronze – matched multi-metal VCI films are required [2], [4].

Modern specialty VCI films are formulated free of nitrites or free of both nitrites and amines and act on both sides, so packers do not need to observe a specific film orientation [2], [4], [6]. To prevent mix-ups with standard PE packaging film on the shop floor, VCI films are often supplied with a transparent tint (e.g. translucent blue, green or yellow) while remaining see-through for part identification [4], [6].

Practical rules for application, storage and process limits

For the VCI protective atmosphere to work reliably, workpieces must be dry, clean and free from existing rust, fingerprints and acid residues when packed [1], [5]. Pre-existing corrosion is not reversed by VCI [1]. The package should be closed as tightly as possible by heat-sealing, taping or tying so the gaseous inhibitor does not escape uncontrolled [1], [4].

Direct contact between metal parts and damp wood, acidic paper or corrugated board inside the VCI enclosure should be avoided; wooden pallets and outer crates belong outside the VCI barrier [1], [3]. Under severe climatic fluctuations in sea containers, VCI packaging can be combined with desiccants to bind free liquid condensation [3], [5]. Unused VCI films and bags should be stored cool, dry, protected from direct sunlight and sealed in their original packaging until use [2], [6].

View VCI corrosion protection film and VCI bags