Table of Contents
Reviewed and updated by ICD - Week 44/2026
VCI (Volatile Corrosion Inhibitor) is an anti-rust chemical impregnated or blended into paper, film, bags, foam and vapour-releasing tablets; in sealed packaging, VCI evaporates, spreads through the whole space and settles on metal as an invisible single-molecule layer, so no oil or grease is needed and nothing has to be cleaned off when the pack is opened. It is a common rust-prevention solution for metal parts and machinery in storage and export.
One thing needs saying clearly: VCI is an anti-rust material, not a desiccant. ICD Vietnam does not sell VCI; this article is written so you understand how VCI works, choose the right form, and know when to combine it with calcium chloride desiccant packets placed in the carton, which directly absorb moisture in the enclosed space with metal cargo going by sea.
How vapour-phase rust prevention works
VCI works in three steps. The compound evaporates from the carrier material, diffuses through the enclosed space, then adsorbs onto the metal surface. Koehler and Reinhard (2014) summarise that the effectiveness of a VCI formulation depends on three parameters: a vapour pressure high enough to carry the vapour, the strength of adsorption onto the oxide layer on the metal, and a combination of several VCI substances to cover several protection mechanisms. According to Cortec documents, compounds used as VCI have a vapour pressure of about 10^-7 to 10^-2 mmHg and attach to metal in a layer a few molecules thick.
| Parameter | Role in VCI effectiveness (Koehler and Reinhard, 2014) |
|---|---|
| Vapour pressure | High enough for VCI vapour to travel through the enclosed space to the metal surface |
| Adsorption strength | Attaches to the oxide layer on the metal, directly or after dissolving in a film of condensed water |
| Combination of several VCI substances | A blend that covers several different protection mechanisms on the same surface |
The TIS-GDV packaging handbook (the German transport insurers’ association) describes VCI as polar compounds, organic or inorganic, that sublime from a carrier material, saturate the air in the package and then settle on bare metal surfaces as an invisible single-molecule film, which can reach even hard-to-access places. This film stops atmospheric water molecules touching the metal and evaporates by itself when the pack is opened, so the goods are ready to use at once.
The big advantage over oil and grease: VCI vapour gets into gaps, corners and inner cavities that grease does not reach, and leaves no residue to clean. One limitation to know: VCI protects through the vapour phase, so it only works when the vapour is kept inside the package. An open pack means the concentration is not reached; the study of closed and non-closed systems by Andreev and Kuznetsov (2012) shows that in a space that is not fully closed, the VCI concentration at the surface falls and corrosion can begin.
Forms of VCI and their uses
TIS-GDV lists VCI carriers including paper, board, film, foam and emitters, and also powder, spray solutions and oils.
| VCI form | Main uses |
|---|---|
| VCI paper | Lining and wrapping mechanical parts, bearings, steel coils; separating metal from acidic carton or wood |
| VCI film and bags | Sealing components, large machinery, container lining; anti-static versions for electronics |
| VCI powder | Scattered into hollow cavities, tanks and large pipes at a dose by volume |
| VCI tablets and emitters | Placed in electrical cabinets, control boxes and narrow spaces needing local protection |
| VCI foam and oil | Cushioning that is also anti-rust; VCI oil for spraying or dipping parts |
An example of emitter dosage: one manufacturer recommends 1 emitter of type 5 for every 5 cubic feet (about 0.14 cubic metres) of package volume, with more possibly needed depending on the environment, how well sealed it is and the condition of the parts, and testing before use is always advised. This figure is only an example for one specific product; each manufacturer has its own dosage table, so read the documents of the product you buy.
Choosing VCI by type of goods
Small parts such as bearings, screws and stampings should use sealed VCI bags or film so the environment holds a stable concentration. Large machinery with hollow cavities (motors, electrical cabinets, tanks, pipes) should be wrapped on the outside in VCI film and have VCI powder or tablets placed into the inner cavities, because when the volume is large or the distance is long, TIS-GDV advises adding VCI carrier material. Sensitive electronics should use anti-static VCI bags.
VCI for ferrous metals and multi-metals
There are VCI types made for ferrous metals (steel, cast iron) and multi-metal types that also protect non-ferrous metals such as aluminium, copper and zinc. Using the wrong type may be ineffective or react with non-ferrous metals, so the right formulation must be chosen for the metal to be protected. The concern is real: a 2018 scientific review recorded that VCI sometimes accelerates corrosion on non-ferrous metals and alloys.
The FAQ document of one emitter manufacturer shows the usual classification: the multi-metal type protects steel, copper, zinc and many lead and tin alloys, but is not recommended to protect silver from sulphur tarnish, and always advises testing in each application. This is an example for one product, not a general rule.
| Goods to protect | Choose | Note |
|---|---|---|
| Steel and cast iron only | VCI for ferrous metals | Make sure it is pure steel, with no aluminium or copper parts mixed in |
| Aluminium, copper, zinc or goods mixing several metals | Multi-metal VCI | Test first on sensitive alloys according to the manufacturer’s documents |
| Sensitive electronics | Anti-static VCI bags | Check compatibility with the specific components |
TIS-GDV also notes two points when choosing products: choose VCI that contains no nitrite, heavy metals, halogens, silicates or substances that must be labelled, and VCI products from different makers are not chemically compatible, so use only one maker in one package.
Correct use and combining with desiccant
Tight sealing is the key factor: use a heat sealer or a special tape for bags and film, because an open pack lets the VCI vapour disperse outside and lose its effect. The metal surface must be dry and clean before packing, since VCI does not replace cleaning. For long sea voyages, combine desiccant to bring the overall humidity down, because the two mechanisms complement each other: VCI protects the metal surface, desiccant reduces the moisture in the enclosed space. Choose the type and dose of desiccant according to the articles on desiccant and in-carton desiccant packets.
| VCI | Desiccant beads and packets | |
|---|---|---|
| Action | Evaporates and attaches to metal as a single-molecule film | Absorbs moisture from the air inside the sealed pack |
| Conditions for effectiveness | Sealed packaging, dry clean surface, the right type of metal | Sealed packaging, enough desiccant for the volume and the journey |
| When used together | Protects the metal surface | Lowers the overall humidity of the enclosed space |
Protection time depends on the product and how well it is sealed; there is no single figure. One emitter manufacturer states protection of about 2 years under ordinary packaging conditions, while also stating that VCI will eventually run out and that the tighter the pack, the longer the protection. So ask the supplier for the protection time under your own conditions rather than relying on a round number.
Common mistakes
First, packaging that is not sealed, so parts still rust despite VCI. Second, wrapping only the outside of a large machine and forgetting to put VCI powder or tablets into the inner cavities, where it is still damp and rusts. Third, packing while the surface is still damp or oily. Fourth, using ferrous VCI for aluminium or copper goods.
Fifth, opening the pack to inspect and not resealing it, letting the active substance escape. Sixth, mixing VCI from several makers in the same package, whereas TIS-GDV states that products from different makers are not compatible with each other.
Frequently asked questions
How does VCI differ from applying rust-preventive oil?
VCI protects by vapour, so it covers gaps and inner cavities, leaves no grease and needs no cleaning on opening; oil only protects the surfaces it touches and has to be removed before use.
Which metals can VCI be used for?
There are types for ferrous metals (steel, cast iron) and multi-metal types that also cover aluminium, copper and zinc. The right formulation must be chosen for the metal to be protected, with testing first on sensitive alloys.
Why does cargo still rust when VCI is used?
Usually because the packaging is not sealed so VCI vapour escapes, or a large machine is only wrapped on the outside and no VCI powder or tablets are placed in the inner cavities; packing while the surface is damp or dirty also reduces effectiveness.
How long does VCI protect for?
It depends on the product and how well it is sealed; there is no single figure (one emitter manufacturer states about 2 years under ordinary packaging conditions). Ask the supplier for your actual conditions.
Is it necessary to use VCI together with desiccant?
It is advisable for cargo going by sea: VCI forms a protective layer on the metal surface, desiccant brings the overall humidity down, and the two mechanisms complement each other.
How far from the metal should the VCI carrier be placed?
According to the TIS-GDV handbook, no more than about 30 cm; for large volumes or long distances, use additional VCI carrier material.
Contact ICD Vietnam
ICD Vietnam Industrial Manufacturing Co., Ltd. - advice on pallets, plastic crates, PE film, forklifts and packaging solutions.
Hotline: 0983 797 186 / 090 345 9186
Email: sales@icdvietnam.com.vn | Zalo: Chat on Zalo
References
- TIS-GDV, Securing the packaged goods, inner packaging, section 4.4.3 The VCI method - tis-gdv.de
- Cortec, Vapor Corrosion Inhibitors: fundamentals (vapour pressure, Fed. Std. 101C Method 4031) - cortecvci.com
- S. Koehler, G. Reinhard, VCI containing package material - mode of functioning (2014) - doi.org
- N. Andreev, Yu. Kuznetsov, Volatile inhibitors of metal corrosion II (2012) - DOI 10.17675/2305-6894-2012-1-2-146-153
- Review of Volatile corrosion inhibitors for ferrous and non-ferrous metals and alloys (2018) - DOI 10.17675/2305-6894-2018-7-2-2
- DLA ASSIST, MIL-PRF-3420, Wrapping Materials, Volatile Corrosion Inhibitor Treated, Opaque - quicksearch.dla.mil
- E. Lyublinski, Evolving standard test methods for vapor inhibiting ability (NACE TM0208-2008) - zerust.com
- Daubert Cromwell, What is an emitter (emitter dosage, service life) - daubertcromwell.com
