Coating-Weight & Galvanizing Fraud
Galvanized or coated steel is sold with a stated zinc coating (e.g. Z275) but ships far thinner, failing corrosion requirements.
How the scam works
- 1.Order specifies a coating weight such as Z275 / G90 for corrosion life.
- 2.Supplier quotes the spec but produces a thinner, cheaper coating.
- 3.Certificate cites the contracted value; actual coating is never that high.
- 4.Premature rust appears within months of installation.
Red flags to watch for
- Price is well below the realistic cost of the stated coating weight.
- Supplier avoids third-party coating-thickness testing.
- Coating mass figures are identical on every certificate regardless of coil.
How to protect yourself
- Test coating mass independently (triple-spot test per ASTM / ISO).
- Benchmark the quote against realistic zinc cost for the coating class.
- Add coating tolerance and rejection terms to the contract.
In depth
Coating-weight fraud targets galvanized and coated coil sold against a stated coating class such as Z275, G90, or AZ150. The steel ships with far less zinc or aluminium-zinc than specified, but because the shortfall is invisible to the eye and the certificate reads correctly, the buyer accepts the load. The cost arrives later as premature rust and corrosion failures, long after the supplier has been paid.
Because the deception is purely in the coating mass, the only reliable defense is to measure it. Write the exact coating class and tolerance into the contract, then commission an independent coating-mass test on random coils at delivery and reconcile the result against the mill certificate. Treat vague or missing coating tolerances in a quotation as a warning sign in their own right.
Related reading
Frequently asked questions
- How do I check the zinc coating weight on galvanized steel?
- Test the coating mass independently using a triple-spot test per ASTM or ISO. Benchmark the quoted price against the realistic zinc cost for the coating class — a price well below that is a strong warning sign — and add coating tolerance and rejection terms to the contract.
- What does Z275 mean on galvanized steel?
- Z275 denotes a zinc coating mass of 275 g/m² total on both sides, which drives the corrosion life of the product. Fraudulent suppliers cite the spec on the certificate but apply a thinner, cheaper coating that rusts early.
Real cases
Coating 40% below spec
Pre-shipment inspection was approved, but independent testing on arrival showed the zinc coating 40% below specification. The MTC looked legitimate, yet its heat number belonged to a different order three months earlier.
Z275 that rusted in months
Accessible coils tested at Z260-280, but once roll-forming began the middle coils showed Z90-120 — most of the shipment was reject coil capped with spec material at both ends.
Worried this is happening to you?
Run your supplier through the structured verification checklist.