Quality control for cookware clad metal
Most clad metal disputes are specification disputes. The material behaves as it was written, and the writing was incomplete. This page sets out what a specification should contain, what inspection covers, and which documents come with a batch.
At a glance
Specification at a glance
| Check | What it covers | Stated in |
|---|---|---|
| Incoming material | Grade, thickness, surface of each layer | Mill certificate |
| Thickness | Total and per layer | Inspection record |
| Dimensions | Diameter or blank size, tolerance | Inspection record |
| Surface | Finish, pattern depth, rim width | Inspection record |
| Flatness | Measurement method and limit | Order specification |
| Bond quality | Method, sampling, acceptance criteria | Test report |
| Compliance | ROHS, REACH, food contact by grade | Test reports |
| Traceability | Batch to coil and to shipment | Batch record |
The quality system
The plant was certified by SGS in 2016 and passed ISO 9001:2015 certification in 2020. Both are management system certifications: they say a process exists and is followed, not that any particular sheet meets any particular number. The numbers come from the product specification.
Test documentation held for the material grades covers ROHS for 304, 430, 439, 1050 and 3003, REACH for 430, 439, 1050 and 3003, and food-contact testing for 304, 430, 439 and 3003. Reports are supplied against the grades in your order.
Quality starts with the agreed specification
A clad specification should define the grade of each layer, the layer order, the thickness of each layer, the total thickness with tolerance, the dimensions with tolerance, the surface finish per face, the flatness limit and the forming process the material has to survive.
If one of those is missing, the first batch becomes the specification by default, and every later batch is measured against something nobody wrote down. That is how a technically correct material ends up rejected.
Inspection items
Inspection covers incoming material verification, thickness measurement, dimensional inspection, surface inspection, flatness checks and bond quality testing. On etched and embossed products it also covers pattern depth, pattern area and the rim width, because those are what the customer sees.
Where a check is done by batch rather than by piece, say so in advance. A buyer sampling five discs from a pallet is testing the batch, not each disc, and the acceptance criteria should reflect that.
Bonding quality, and the number that is not on this page
For a clad material, the bond between layers is the technical concern that matters most, because delamination appears after forming, not before. Bond quality is assessed by shear, bend or peel tests depending on the structure, and the method and criteria are stated with the batch documents.
We do not publish a single bond strength figure. A value that applies to one structure and one test method would be read as a promise for every structure, which is how a material gets rejected for missing a number it never had.
Documents and traceability
Documents supplied with a batch can include the material certificate, the technical data sheet, the inspection record, ROHS or REACH reports and food-contact test reports. Each identifies the material, the batch, the test method, the issuing body and the date.
Traceability runs from the batch back to the raw coil and forward to the shipment. If your customer requires batch-level traceability, state it in the enquiry, because those records are generated during production and cannot be reconstructed later.
Questions
Common questions
Do you have ISO 9001?
Yes, ISO 9001:2015 since 2020, and SGS certification since 2016. Certificates are supplied on request.
Which compliance reports are available?
ROHS for 304, 430, 439, 1050 and 3003; REACH for 430, 439, 1050 and 3003; food-contact testing for 304, 430, 439 and 3003. Ask for the reports that match your grades.
What bond strength can you guarantee?
Bond requirements are set per structure and per test method, and stated with the acceptance criteria in the quotation. A single site-wide figure would not describe any specific material.
Is the material food-contact compliant?
Food-contact reports are held for the stainless and aluminium grades listed above. Compliance also depends on the destination market and on the finished cookware, so state the market in the enquiry.
How do I complain about a batch?
Send the batch reference, photographs and the measurement that fails. Claims are reviewed against the agreed specification, which is why the specification is written before the first order.