Sourcing Stainless Steel Sinks from China: 12 Checks Before You Order

China produces the majority of the world’s stainless steel kitchen sinks, and the quality range within that output is enormous. Two factories a kilometre apart can produce sinks that look identical in a photo and behave completely differently after two years of use.

This is a checklist for the point where you have shortlisted suppliers and are deciding who gets the first order. It is ordered roughly by how much damage a mistake in each area will do.

1. Confirm you are talking to a factory, not a trader

A large share of “manufacturers” on B2B platforms are trading companies. That is not automatically disqualifying — some traders add real value in logistics and quality control — but it changes what you are buying and what recourse you have.

Three cheap tests. Ask for the business licence and check whether the registered scope includes manufacturing (生产) or only trading (贸易). Ask for a video call walked through the production floor, live, not a pre-recorded clip. Ask a technical question that only a producer would answer easily — for example, what passivation method they use after welding, or what tonnage their press is rated for.

A trader will defer or generalise. A factory will answer specifically and possibly at length.

2. Get the mill certificate, and match it to the invoice

Stainless grade is the most commonly substituted specification in this product category. 201 is sold as 304 with regularity, and the price difference is significant.

Ask for the mill test certificate for the coil or sheet used in your order, and check three things: the grade matches what you ordered, the certificate is for the actual heat number used, and the chemistry is plausible (304 should show roughly 18 percent chromium and 8 percent nickel).

Then verify independently. A handheld XRF analyser will identify the grade in seconds. These are cheap to hire in most markets, and if you are placing a container order, the cost is trivial against the risk.

Note that 304 is only weakly magnetic and 201 is more magnetic, but this is not a reliable field test — cold working makes 304 magnetic too. Use XRF.

3. Verify gauge by weight, not by description

Gauge is the second most commonly substituted specification. A 1.2 mm sink sold as 1.2 mm may be 1.0 mm, and you cannot tell by looking.

Put a weight tolerance in the purchase order. Calculate the theoretical weight from the sheet area and thickness, allow 3 to 5 percent, and specify that units outside that band are rejected. Weight is the only thickness check that can be done on a loading dock in thirty seconds, and its existence in the contract changes supplier behaviour before shipping.

For a one-off verification, ask for a section cut from a production unit at the bowl wall and at the base radius, and measure with a micrometer. A supplier who refuses is telling you something.

4. Inspect welds properly on welded sinks

If you are buying handmade (welded) sinks, the weld is the product. Four checks:

Visual, under raking light. Look along the corner seam. A good weld is dressed flush with no shadow line, no pinhole, and no heat discolouration.

Fingernail test. Run a nail along the inside joint. It should transition smoothly. A catch means the weld was not dressed.

Salt test. Put a few drops of strong salt solution on the weld and leave it warm overnight. Rust staining indicates the passivation step was skipped or poorly done. This test costs nothing and catches more bad factories than any audit form.

Section a sample. Cut through a corner weld and look at penetration. Partial penetration is a pinhole waiting to open.

5. Check the passivation story, not just the polishing

Welding destroys the chromium oxide layer in the heat-affected zone. Passivation restores it. Without it, the sink will rust along the seam — not catastrophically, but visibly, which is worse because it looks like a defect rather than wear.

Ask what passivation method is used: nitric acid, citric acid, or electrochemical. Any answer is acceptable as long as there is a controlled process and a rinse step. “We polish it well” is not a passivation answer.

This is the single most common cause of the complaint that a sink “rusts at the corners after six months”.

6. Confirm the drain and overflow specification for your market

Drain diameter varies by market — 3.5 inch (90 mm) for most Western markets, 114 mm for some Asian markets. Overflow is standard in Europe and optional in North America.

Two failure modes. A wrong drain diameter cannot be adapted on site. An overflow that is present when the market does not want it is a small annoyance; an overflow that is absent when required fails inspection.

Specify both explicitly in the purchase order, with a drawing, rather than relying on “standard”.

Also check the strainer. A stainless or brass-bodied strainer with a proper gasket will last; a chrome-plated zinc one will not. Ask for the body material in writing.

7. Test the actual export carton

Packaging is where a good sink becomes a damaged sink, and the failure is invisible until the container is opened.

Ask for a drop test on the packed carton from the actual packing line — flat drop and corner drop, from about 1.2 m. Then open the carton and inspect the sink. A drop test that dents the product is a failed test regardless of whether the carton survived.

For thin gauge or mirror finish, confirm protective film and foam sheet. For drainboard sinks, confirm centre bracing, because a long flat panel with no depth is the most drop-sensitive shape in the range.

8. Check certifications against your actual channel

Certification requirements depend on where and how you sell:

• EU: food-contact material compliance, REACH.
• US: California Prop 65 labelling; NSF certification for some channels and commercial applications.
• UK: WRAS for any component connected to mains water.
• Australia: WaterMark for plumbing products in some categories.

Ask which certificates the factory holds and request the certificate numbers so you can verify them with the issuing body. A scanned certificate with no number, or one issued to a different company name, is not evidence.

Certification cannot be retrofitted cheaply after a container has shipped.

9. Assess capacity against your order size

A factory that produces 3,000 sinks a month and takes your 5,000-unit order will either deliver late or subcontract part of it. Subcontracting is where quality control disappears.

Ask: current monthly output, current order backlog, number of production lines, and whether any process is outsourced (polishing and PVD coating are often outsourced).

Then ask for two recent shipping documents for comparable orders, and check the dates against what they told you about lead time.

10. Agree lead time with a buffer, in writing

Standard repeat-order lead time for welded sinks is 25 to 40 days, plus transit. First orders with new sizes or new packaging take longer.

Put the ship date in the contract with a defined consequence for lateness. The most common first-order mistake is booking freight against an optimistic production date, then paying for air freight or storage.

11. Inspect before shipment, not after arrival

Third-party inspection before loading typically costs a few hundred dollars and catches problems while they are still fixable at the factory.

The inspection should cover: quantity, dimensions against drawing, gauge by weight, finish consistency, weld quality on a sample, drain and overflow specification, carton condition, and shipping marks.

If you skip this on the first order, you will pay for it on the second.

12. Define the after-sales position before you need it

Ask what happens when a unit is defective: replacement, credit, or repair. Ask what the defect rate threshold is for a claim, and what evidence they require.

A supplier who has a documented policy has dealt with this before. A supplier who says “no problem, we guarantee quality” has not thought about it.

Also confirm spare parts availability — strainers, clips, and for workstation sinks, accessories. These are the parts that generate after-sales tickets, and they are cheap to stock if you plan for them.

The one question that reveals the most

If you only ask one thing, ask this: *”Send me a section cut from a production sink at the bowl wall and at the base radius, with the thickness measured.”*

It tests whether they control gauge, whether they understand why thickness varies, and whether they are willing to show you production reality rather than a marketing sample. Factories that answer well are usually good on everything else.

Next step

We manufacture in Guangzhou and supply importers, distributors, and project buyers in 304 and 316, in welded and pressed construction. We provide mill certificates, weight-per-unit tolerance in the purchase order, and section measurements on request. If you are qualifying suppliers, send us your specification and we will quote with the technical documentation attached rather than a price alone.