Ask for paperwork on bulk orders
A mill test certificate states the actual composition and grade of a batch — the single most reliable way to confirm what you're getting on any sizeable order.
The magnet check (limited but useful)
Austenitic grades like 304 and 316 (the most common architectural grades) are only weakly magnetic or non-magnetic, while lower-grade or fake "stainless" material is often strongly magnetic. This isn't conclusive on its own — some genuine stainless can show slight magnetism after forming — but a strongly magnetic piece sold as 304/316 is a red flag worth questioning.
Visual and tactile checks
- Consistent finish across the whole piece, no dull or patchy sections.
- Weight feels appropriate for the stated thickness — noticeably light can indicate thinner material than specified.
- Edges are clean-cut, not rough or burred, which reflects fabrication quality more than the steel itself but is a reasonable proxy for supplier care.
The most reliable signal
Buy from a supplier that also fabricates with the material it sells (see our supplier guide) — they have their own reputation riding on the material performing, which is a stronger incentive than a pure reseller has.