Why bearings rust in transit
Bearing rings and rolling elements are made of high-carbon chromium steel that is hard, ground to a fine finish and not corrosion-resistant. Any film of water on a raceway can leave a mark that becomes a pit, and pits become noise and early fatigue. During a sea voyage the cargo passes through hot and cold zones, and humid air condenses on cold metal inside a closed container, a phenomenon often called container rain. Even a short period of condensation can damage unprotected steel.
So packaging for bearings has two jobs. The first is chemical: to prevent rust with an oil film, a vapour-phase inhibitor or both. The second is mechanical: to keep the pieces from hitting each other, from crushing carton corners and from shifting on a pallet. A good pack does both and still allows easy counting and identification at the receiving end.
The layers of an export pack
A typical pack is built from the inside out. Each layer solves a specific problem, and a missing layer usually shows up as a claim.
| Layer | Purpose | Typical materials |
|---|---|---|
| Surface protection | Stops corrosion on rings and rolling elements | Anti-rust oil film, rust-preventive grease |
| Inner wrap | Holds the oil, keeps out dust and moisture | VCI paper, oiled paper, plastic sleeve |
| Inner box | Individual identification and protection | Cardboard or plastic box, labelled |
| Bag or shrink wrap | Second moisture barrier for a set of boxes | VCI bag, polybag, shrink film |
| Outer carton | Carries weight, stacking and handling | Strong corrugated cartons, strapped |
| Pallet | Unit load for forklift and container | Wooden pallet, stretch wrap, corner protection |
Which layers are used depends on the bearing size, the route, the value and the buyer's brand packaging, which is discussed in private label bearings.
Anti-rust oil: the first line of defence
Most bearings leave the plant with a thin film of preservative oil on the surfaces. The oil is applied after washing and drying, and it should be compatible with the grease or oil that will be used in service, or easy to remove before assembly. Open bearings carry more oil than sealed ones, because the sealed type already holds grease inside. The film should be thin and continuous: too thin and it gives gaps; too thick and it makes handling messy and attracts dust.
The oil also affects the user. Some workshops dislike oily hands and expect clean, dry-feeling parts; others expect to see a film as a sign of protection. Agree the preservation type with the supplier and the end user, and keep the specification in the order file. Preservative should not be mistaken for lubricant: an open bearing still needs proper lubrication at assembly. Grease basics are in the lubrication guide.
VCI paper and bags
VCI stands for volatile corrosion inhibitor. VCI paper and VCI film release molecules that settle on metal surfaces inside a closed space and form a very thin protective layer. The effect works as long as the space stays closed, so the bag must be sealed and not torn. VCI is useful for sets of bearings, kits and mixed shipments, and as a second protection layer on top of the oil.
- Use VCI inside a sealed bag or a closed box; open VCI paper in an open carton does little.
- Keep the bearing dry when it is wrapped. VCI does not remove water that is already on the metal.
- Check that the VCI grade suits the materials. Some types are not recommended for certain non-ferrous metals, so ask the plant when brass cages or copper parts are present.
- Keep VCI bags away from damp, direct sun and heat while stored, since the active ingredient is volatile.
The VCI approach is often combined with desiccant packets in the outer bag for long sea routes, particularly into humid destinations.
Inner boxes, cartons and pallets
Inner boxes keep each bearing from knocking against its neighbours and carry the identification label. Designations, quantities and batch codes should be printed or labelled clearly. Outer cartons must resist stacking pressure in a container; bearings are dense, so cartons are usually smaller than expected and weight per carton is controlled to keep manual handling safe. Strapping and corner protection stop collapse.
Palletised cargo should use a pallet that meets the destination rules for wood treatment, stretch-wrapped, with the cartons laid in a stable pattern and no overhang. Mixed designations in one carton are an inspection and picking risk; where mixing is unavoidable, use separators and a packing list in the carton. Pallets sent by sea benefit from a moisture barrier film or bag over the full load. Route and transit guidance is on the logistics page.
Sea, air and courier: different risks
The route changes what the pack must survive. Sea freight is the longest exposure to humidity and temperature swings, so it calls for the full set of oil, VCI and moisture barrier, with desiccant on humid lanes. Air freight is shorter, but handling is rougher and cartons are loaded and unloaded several times; strong cartons and tight inner packing matter more than extra moisture protection. Courier samples travel in small parcels, so each bearing should be oiled, wrapped and boxed individually, with enough cushioning that a drop does not mark the raceway. Reference transit times for each route are on the logistics page and are confirmed per shipment.
Whatever the route, avoid reusing old cartons, avoid placing heavy cartons on top of weaker ones, and keep oil-stained cartons apart from printed branded boxes. Small habits in packing prevent most of the claims that reach a sourcing desk.
Checks on arrival and in storage
- Inspect the pallet and cartons for crushing, moisture marks or damage before signing for the goods.
- Open a sample carton from each pallet and check for rust, loss of oil film and loose wrapping.
- Reseal opened VCI bags and re-wrap partly used cartons.
- Store in a dry, temperature-stable room, off the floor; the shelf-life note covers the details.
- Photograph any damage and report it quickly with the batch and carton numbers.
The same checks apply to goods leaving the plant and are part of the pre-shipment inspection. If transit damage seems linked to movement rather than rust, see false brinelling in transit.
Specifying packing in your order
State the route, the climate at the destination, the expected storage time and the format you need: neutral or branded boxes, VCI or oiled paper, number of pieces per box and carton, pallet size and any limit on carton weight. The desk will confirm packing for each program in writing and check it at inspection. Send the details through the quote form.