Packing and Shipping Cast Iron Engine Parts: Crates, Rust Prevention and Container Loading

Three questions come up in almost every inquiry after the price is settled: will the parts rust on the way, how many tons fit in a container, and how long from finished goods to a ship. They sound like details. They decide whether the shipment arrives in saleable condition.

This guide covers how cast iron engine parts — flywheels, ring gears, flywheel housings, timing gear housings, cylinder blocks and heads — are packed, protected and loaded at Qingdao. The numbers are the ones we use when quoting.

1. Cast iron is weight cargo, not volume cargo

The first thing to understand about shipping castings is density.

Material	Density (g/cm³)	1 m³ of solid metal
Grey iron (HT250 / Class 35)	7.20–7.35	7.2–7.35 t
Ductile iron (QT500-7 / 80-55-06)	7.10–7.20	7.1–7.2 t
Carbon steel	7.85	7.85 t
Aluminium	2.70	2.70 t

A 20GP container holds about 33 m³. Fill it with solid iron and you would have 237 tonnes. The container’s own weight limit is somewhere around 21 to 28 tonnes depending on the carrier.

So a castings container hits its weight ceiling long before it runs out of space. This changes the whole packing logic. With textiles or plastic parts you try to fill volume. With castings you try to fill weight, and every kilogram of packaging is a kilogram of product you cannot load.

That is why export packing for castings looks sparse compared with other industries: no thick foam, no oversized cartons, no pallet for every part.

2. Packing by part weight

Packaging is chosen by unit weight, not by part name. A 6 kg ring gear and a 380 kg cylinder block are not the same problem.

Part type	Typical unit weight	Packing used	Stacking
Ring gears, pulleys, small gears	2–15 kg	Carton + stretch film + PP strap, on a wooden pallet	5–8 cartons high
Small and mid-size flywheels	20–60 kg	Pallet + stretch film + steel or PP strapping	1–2 layers
Large flywheels (European, high-horsepower)	60–150 kg	Plywood case with skids, one part per case or nested with separators	Single layer
Flywheel housings, timing gear housings	15–80 kg	Pallet with cartons, or plywood case	1–2 layers
Cylinder blocks and heads	80–400 kg	Plywood case, reinforced with timber, one part per case	Single layer
Very heavy items over 200 kg	>200 kg	Steel frame, or heavy-duty case, strapped to a pallet base	Single layer

Two rules sit underneath this table.

Machined faces never touch anything hard. The friction face of a flywheel, the tooth flanks of a ring gear, a cylinder bore, a seal face — these are the surfaces your customer inspects first. Every one of them needs paper, cardboard or PE foam between it and the next part.

Nothing heavy sits on a cardboard box. A 90 kg flywheel on top of a carton will crush it in a warehouse, and the damage shows up at the destination port.

For flywheels specifically, we put a support under the centre hub if the part is stored vertically, and never let the rim carry the whole weight. A flywheel that has been leaning on its rim for two months at sea can come out with a runout problem before it is ever bolted to a crankshaft.

3. Rust: cast iron is not the problem, machined surfaces are

There is a common assumption that anything made of iron will arrive rusty. In practice, the opposite is often true. As-cast grey iron surfaces carry a dense oxide skin and free graphite, and a flywheel can sit in a yard through a rainy season with nothing worse than a dull grey appearance.

The rust risk sits on the machined surfaces, where fresh metal is exposed: flywheel friction faces, ring gear tooth flanks, cylinder bores, sealing faces, bolt-hole threads, keyways.

Three levels of protection, chosen by transit time and destination climate:

Transit time	Protection	Typical destinations
Under 30 days	Rust-preventive oil, thin film, applied after cleaning and drying	Southeast Asia, Korea, Japan
30–60 days	Rust oil + VCI (vapour corrosion inhibitor) film + desiccant	Middle East, Africa, Europe, Russia
Over 60 days, or hot and humid	Paint or zinc-flake coating on exposed faces + VCI film + foil vac-bag	Latin America, equatorial regions, long-term storage

Three things go wrong most often with VCI film, and all three are avoidable:

The film has to be sealed. VCI works by saturating a closed air space with inhibitor vapour. A loosely draped sheet releases the vapour and protects almost nothing. Folded, taped, closed.

The part must be at or below ambient temperature before wrapping. Wrap a hot casting and the moisture in the air inside the film condenses on the metal overnight. You have built a humidity chamber.

Oil goes on dry metal. Cleaning fluid, coolant and rinse water all have to be gone first. Oil applied over a wet surface traps water underneath and produces rust under a perfect-looking film of grease.

If your customer’s incoming inspection includes a salt spray test, say so at the quotation stage. Neutral salt spray to ASTM B117 at 24, 48 or 72 hours is a standard request and it changes what we apply. Adding it after the parts are packed means repacking the whole order.

4. How many tons fit in a container

	20GP	40HQ
Internal dimensions (approx.)	5.90 × 2.35 × 2.39 m	12.03 × 2.35 × 2.69 m
Usable volume	about 33 m³	about 76 m³
Common maximum payload	21,000–28,000 kg	24,000–28,600 kg
Realistic castings load	about 20–24 t	about 22–26 t

The conclusion surprises most first-time buyers: the 40HQ has about 2.3 times the volume of a 20GP, but only a little more payload. Load castings into a 40HQ and you ship half a container of air.

For dense castings, the 20GP almost always wins on freight per tonne. The 40HQ makes sense when the parts are individually light — small ring gears, pulleys, timing marks — or when the order is consolidated with other cargo.

A worked example. Mid-size flywheels at 56 kg each:

Basis	Calculation	Units per 20GP
22 t payload	22,000 ÷ 56	about 390
20 t payload (inland road limits)	20,000 ÷ 56	about 350

The second row matters more than the first in some markets. Several countries limit the gross weight of a truck on public roads, and a container that is legal at the seaport can be illegal 200 km inland. If your goods move by truck after discharge — and in Africa, inland Latin America and parts of Southeast Asia they usually do — confirm the road limit before booking, not after.

The payload figures above are common carrier values. The binding number is on the booking confirmation and the bill of lading. Load estimates for castings assume roughly 45 to 60 percent solid fill inside the container, which varies with part shape; a flat flywheel stacks far denser than a hollow housing.

5. Inside the container: securing the load

Wrap film alone does not hold 22 tonnes in place during a sea crossing. What holds it is timber and strapping.

Pallets or cases are bedded on timber dunnage so the load does not sit directly on the container floor. Strapping runs to timber battens wedged against the container walls, never to the wall itself. On heavy cases we use steel strapping; on palletised cartons, heavy PP.

Ring gears need their own rule. A nicked tooth flank becomes a noise source once the gear is pressed onto a flywheel and the engine is running. Gears travel with cardboard or foam separators between every layer and every row.

The last two rows at the door end get dunnage bags or timber blocking. A gap of 30 to 50 cm at the door lets the load shift forward on the first heavy swell, and 22 tonnes of castings arriving in a heap is a claim waiting to happen.

6. Wood packaging and ISPM 15

Solid wood packaging — pallets, battens, timber-reinforced cases — must comply with ISPM 15 for most destination countries. Untreated solid wood can be held, fumigated at the consignee’s expense, or refused entry.

The simple way around it is to avoid solid wood as the primary packaging material. We build the majority of export cases from plywood, which is processed and therefore exempt from fumigation. Solid wood, where used for battens or skids, is heat treated and marked under IPPC.

A plywood case saves a process step and a couple of days, and removes one entire category of destination-port problem.

Documents that normally travel with a castings shipment: commercial invoice, packing list, contract, certificate of origin, and the material certificate. For castings we issue an EN 10204 3.1 certificate covering heat number, grade, chemical composition and mechanical properties, plus dimensional and hardness reports where the drawing calls for them.

7. FOB Qingdao: from finished goods to sailing

Step	Typical time
Final inspection (dimensions, hardness, visual, runout)	1–3 days
Booking	3–5 days off-peak, 7–10 days in peak season
Packing and delivery to port	1–2 days, plus 2–3 days before vessel closing
Customs clearance	1–2 days
Sailing to bill of lading	3–7 days after departure

Indicative transit times from Qingdao:

Destination region	Transit time
Southeast Asia	5–10 days
Korea, Japan	3–7 days
Middle East	15–22 days
Africa	25–40 days
Europe	30–40 days
Latin America	30–45 days

Transit times move with carrier, route and season. Treat the table as a planning range, not a commitment.

8. Six packing mistakes that cost buyers money

Mistake	What it costs
Solid wood packaging with no IPPC mark	Hold at destination, fumigation charge, storage days
Stretch film only, no VCI on machined faces	White rust on opening, claim and rework argument
Pallet or case over the weight or dimension limit	Rejected at the loading dock, manual handling surcharge
Shipping marks missing carton or case numbers	Packing list cannot be reconciled at receiving
Heavy parts stacked on cartons	Crushed bottom layers, damaged machined faces
Mixed part numbers in one case with no separation	Sorting by eye, wrong parts fitted

9. FAQ

Q: Will cast iron parts rust during sea freight?

As-cast surfaces normally will not. Machined surfaces will if they are unprotected, especially in a container that crosses climate zones. We apply rust oil plus VCI film for longer routes, and will add salt spray testing if your incoming inspection requires it.

Q: How many tons of flywheels fit in a 20GP?

Between about 20 and 24 tonnes, depending on the carrier’s payload limit and the road weight limit at destination. For a 56 kg flywheel that is roughly 350 to 390 pieces.

Q: Do the wooden cases need fumigation?

Plywood cases do not. If solid wood is used, it is heat treated and marked to ISPM 15. Ask before the order ships if your country has additional requirements beyond ISPM 15.

Q: Can you pack to our specification?

Yes. Customer marks, carton printing, case dimensions, pallet type, layer separators and rust protection level can all be specified. Send the packing requirement with the inquiry so it goes into the quotation.

Q: Does the packaging affect MOQ?

It can. Custom carton printing and custom case sizes have their own minimums. Standard export packing on castings has no MOQ beyond the order quantity itself.

Q: What quality documents come with the shipment?

An EN 10204 3.1 material certificate with heat number, chemical composition and mechanical properties. Dimensional, hardness and runout reports where the drawing specifies them. IATF 16949 process documentation is available for automotive programs.

10. Getting a shipping estimate

Tell us the part numbers, the quantity, and the destination port. We will come back with unit weight, packing method, total gross weight and the container configuration that gives the lowest freight per tonne — usually a 20GP, occasionally two 40HQs, sometimes a mix with the customer’s other cargo.

Factory: Changyi Wangke Industrial Zone, Weifang, Shandong, China
Port of loading: Qingdao
Email: [email protected]
Phone / WeChat / WhatsApp: +86 19953662121

Related reading:
– Cast iron grade conversion: HT250 and QT500-7 against ASTM, EN, JIS and GOST
– Ring gear manufacturing process and quality control
– Flywheel dynamic balancing: why it matters

Request a quote at https://www.changweiintl.com/en/inquiry