Aluminum Window & Door Inspection in China: Pre-Shipment Guide for Importers
Published October 13, 2026 by muzhuo
Aluminum Window & Door Inspection in China: Pre-Shipment Guide for Importers
Why This Matters
Aluminium windows and doors fail in ways a packing photograph cannot show: a profile 0.4 mm under its specified wall thickness, an anodized coating at half the required micrometres, hardware that seizes in coastal air, or a frame that will not close squarely once the glass is installed.
For importers buying from China for Mexico, Colombia, Chile or Brazil, those defects surface thousands of kilometres away — as rejected lots, on-site rework and warranty claims. A pre-shipment inspection at the factory measures the profile, tests the coating and opens the finished unit while fixing it is still cheap.
What Actually Goes Wrong in Aluminium Shipments
From our inspection files, window and door defects cluster into five families. Most are decided long before the container is loaded:
| Failure mode | Typical cause | What it costs at destination |
|---|---|---|
| Wall thickness below spec | Worn die; alloy saved on the line | Structural rejection, failed load test |
| Alloy grade substitution | 6060 or recycled billet sold as 6063 | Weak corners, patchy anodizing |
| Coating under-thickness | Line speed too fast during anodizing | Chalking, colour shift, corrosion |
| Hardware failure | Unbranded handles, hinges, rollers | Seizing, breakage, warranty claims |
| Dimension drift | Loose cutting and mitre tolerance | Frames that will not square on site |
� The profile is the product. If wall thickness, alloy grade and coating weight are already wrong, no careful packing will rescue the order.
Step 1 — Verify Alloy Grade, Wall Thickness and Geometry
The first checks at the factory are mechanical, and they need instruments, not eyes.
Alloy grade
Ask for the mill certificate and match the heat number to the billets used for your order. Extrusions for architectural work are normally 6063-T5 or 6063-T6; 6060 is a weaker alloy that mills more easily. A handheld alloy analyser or a hardness test on a cut section settles it in minutes.
Wall thickness
Measure the visible wall with a digital calliper and the internal wall with an ultrasonic gauge. Compare every reading to the drawing tolerance — commonly ±0.15 mm for visible walls and ±0.10 mm for structural walls. Record the minimum, not the average.
Profile dimensions
Check overall width, height, camber and twist against the drawing, then measure the mitre angle and the cut length of the finished frames. A frame that is square on the bench will not stay square if the mitre is off by half a degree.
Tip: run the checks on the actual order lot, not on a "golden" sample kept in the office. Samples lie; production runs do not.
Step 2 — Surface Finish: Anodizing and Powder Coating
Finish problems are invisible in packing photos but obvious to sun and salt within months.
Anodizing
Typical architectural anodizing is 10–15 µm for interior and 15–25 µm for exterior exposure (Class 15 / Class 20). Measure with an eddy-current gauge at five or more points per profile length, on different faces. Look for burning, powdering, streak marks and colour variation between bundles of the same batch.
Powder coating
Measure the dry film thickness (commonly 60–80 µm) and run a cross-hatch adhesion test plus a 1 mm bend. Ask for the colour standard and compare against it under daylight — not under factory sodium light, which hides yellow.
| Finish | Minimum thickness | Field failure if missed |
|---|---|---|
| Anodized (interior) | 10 µm | Chalking, dull surface |
| Anodized (exterior) | 15–20 µm | Pitting, whitening, corrosion |
| Powder coated | 60 µm | Chipping, peeling at cut edges |
| PVDF coated | 25–30 µm | Fading, chalking offshore |
Step 3 — Assembly, Glass and Hardware
Hardware
Test the actual handles, hinges, friction stays and rollers fitted to the order. Open and close the unit at least ten times, confirm the locking mechanism engages fully, and check that the handles are the approved brand rather than a look-alike.
Glazing and gaskets
Confirm glass thickness and type against the drawing (tempered, laminated, low-E) and that the gaskets sit evenly without gaps. Check drainage holes, and confirm the unit does not leak when water is poured into the channel.
Overall fit
Place the finished window or door on a flat bench, check the frame for square, and confirm the sash closes without forcing. Record the diagonal measurements so any twist is documented.
� A five-minute water and fit test at the factory costs nothing. Removing a failed window from a tower costs a great deal.
Step 4 — Labelling, Packaging and Loading
- Verify that carton and profile labels match the contract: model, profile reference, colour code, quantity.
- Check for the destination marking your project requires, including importer, project or NOM-related labels.
- Confirm protection: corner guards, interleaved foam, stretch wrap and a pallet that will survive a stack of freight.
- Watch the truck or container load. Stacking aluminium too high, or resting profiles on their thin edge, bows them before they leave the yard.
For a full loading checklist, see our container loading supervision guide.
How the Inspection Is Sampled
Aluminium orders are usually inspected to ISO 2859-1 / ANSI-ASQ Z1.4 at general inspection level II. Because these are large, high-value pieces, many importers run 100 % dimensional and finish screening on frames and AQL sampling on hardware, accessories and packaging. Photographic evidence should follow a fixed set of views — carton, open carton, packed unit, installed detail and full product — as described in our inspection report photo standards.
Want the wider process? Our complete pre-shipment inspection guide covers booking, sampling and reporting end to end.
Frequently Asked Questions
Can you check aluminium windows without opening the packing?
Not fully. Dimensional and coating checks can be done on bundles, but assembly, hardware and fit must be checked on finished, unpacked units. Insist that at least a sample is opened.
What is the most common defect you find?
Wall thickness and coating thickness below specification. Both are cheap to fix at the factory and impossible to hide from a micrometer.
Do you test the alloy grade in the report?
Yes. Where the client needs it, we record hardness readings and, on request, alloy analysis results with the sample reference.
How much time should I allow before the ship date?
Book once frames are assembled and packing has started — ideally five to seven working days before the load cut-off.
Do you inspect specifically for the Mexican market?
We verify labels, importer markings and project-specific requirements against your spec, and we flag anything that will not clear at the destination.
Verify the Frame Before You Pay the Freight
Aluminium defects are invisible in a warehouse photo and obvious on a façade after one rainy season. Measure the profile, test the finish and fit the finished unit at the factory — and you load a product that behaves on site exactly as it did on the line.
→ — dimensional, coating and assembly checks in one visit Book an inspection
→ — we build the checklist around your profile spec Send us your drawing