For most process and architectural specs, AISI 304 cold-rolled stainless — 0.3-8 mm thickness range, 2B finish, certified to ISO and SGS — is the default workhorse grade buyers encounter on RFQs [S2].
The same RFQs almost always miss the cost-versus-corrosion trade-off: stainless carries roughly 4-6× the unit price of hot-rolled carbon steel at the same thickness, and roughly 2-3× the density-driven weight cost of aluminium — facts that govern every downstream fabrication and shipping decision. Where the brief actually calls for a stainless pipe or alloy steel alternative, those numbers shift the engineering case materially.
Corrosion resistance: the load-bearing advantage
Stainless bearings in AISI 420 do not rust under wash-down, survive exposure to many process fluids, and can run submerged in liquids that would destroy a carbon steel race — that washability is the reason food, pharmaceutical and marine OEMs default to stainless for rolling-element hardware [S3]. The mechanism is the chromium-rich passive film, typically ≥10.5% Cr by mass, which re-forms spontaneously in oxygen-bearing environments.
That same passivation does not equal immunity: chloride-rich media (seawater, road de-icing salt, many bleach chemistries) will pit austenitic 304/316 above roughly 50-60°C unless the higher-Ni 316 grade is specified. For applications where galvanic contact with dissimilar metals is unavoidable, see the geometry and isolation rules in this stainless installation guide.
Mechanical and thermal envelope: where stainless outperforms
Stainless ball bearings with a high-temperature polymer cage or full-complement geometry run continuously from 180°F up to 1000°F when paired with high-temperature grease — a range that exceeds standard grease-lubricated carbon steel bearings by several hundred degrees and is the gating spec for oven-conveyor, foundry and after-turbo bearing pockets [S3]. AISI 420 martensitic races add hardness (typically HRC 58+ after heat treat) on top of that thermal headroom.
Austenitic 300-series sheet in 2B finish carries a minimum 515 MPa tensile strength and 205 MPa 0.2% offset yield in the annealed condition, with elongation above 40% in 2 mm sheet — the ductility that lets deep-drawn sinks, elevator panels and brewing tanks form without cracking [S2]. Hot-rolled variants drop the surface finish a step but gain thickness up to 8 mm for structural architectural panels.
Failure modes: the disadvantages engineers have to plan around
Stainless bearing failures cluster into two root-cause buckets: overload fracture and defect-initiated fracture [S3]. Overload traces back to host-machine failure or improper installation (poor fits, misalignment, missing preload); defect fracture traces to micro-cracks, shrinkage cavities, inclusions, overheating or local burns left from forging and heat treatment — quality gates that the buyer's incoming-inspection procedure has to actually enforce.
For sandblasted decorative sheet, the colour drift between blasted and as-plated 304 panels comes from corundum media embedding in the surface and is a known, recurring complaint on architectural orders [S1]. On the structural side, stainless is non-magnetic in the annealed austenitic condition, which forces a rework of any spec that assumed magnetic fixturing or inductive heating — a frequent gotcha for shops that move between mild and stainless work.
Grade selection matrix: 304 vs 316 vs 420 vs 430
Buyers comparing the four most-encountered grades on a real RFQ will usually find the call comes down to four criteria: chloride exposure, required hardness, temperature ceiling, and unit cost. AISI 304 cold-rolled sheet at 0.3-8 mm is the cheapest and most available, SGS/ISO certified, with the broadest 2B and BA finish inventory [S2]. 316 trades roughly 20-30% higher cost for 2-3% Mo addition, lifting pitting-resistance equivalent number (PREN) from ~18 to ~25 and pushing the chloride-pit threshold up by 20-30°C.
For wear-loaded bearing races, AISI 420 martensitic delivers HRC 58+ hardness and the 180-1000°F grease-lubricated envelope noted above, at the price of lower general corrosion resistance than 304 — acceptable in clean, dry, high-temperature service but a poor pick for wet food-zone wash-down [S3]. AISI 430 ferritic is the budget pick for indoor appliance and architectural trim, magnetic (handy for fixtures), but with markedly lower corrosion resistance and a narrower forming window. Where the RFQ is really asking for silicon steel or a magnetic-core application, 430's ferritic behaviour reads completely differently from 304's austenitic curve.
Surface finish and fabrication: how to keep stainless from costing twice
Sandblasted 304 panels — corundum-blasted over a 2B base — are the second-most-ordered finish in colour stainless after electroplating, used in elevator interiors, architectural cladding and industrial housings, with the grain improving perceived flatness and raising decorative value over standard 2B [S1]. Buyers should price the colour-match risk separately: blasted panels almost never colour-match a sister batch of as-rolled sheet, and reorders beyond 6-12 months frequently need re-blasting on the full lot.
For volume procurement, AISI 304 cold-rolled coils ship at 25 t net weight per coil from Chinese mills, with monthly supply capability reported at 20,000 t — useful baselines for any project that needs to confirm allocation before locking a steel fiber or rebar substitution into the BOM [S2]. Hot-rolled 304 plate in 5.0-6.0 mm is the go-to for structural architectural panels, annealed and pickled, and forms the feedstock for many fabricator's polishing lines.
Cost and weight: the unavoidable disadvantages
Stainless costs more per kilogram than mild or galvanised steel and weighs roughly 3× more than aluminium at the same stiffness-limited section. The standard 304 cold-rolled RFQ ships in coils of 25 t net weight — a logistics footprint that smaller fabrication shops must plan around, since the minimum order quantity on the same listings sits at 50 t [S2].
The corrosion-resistance premium is real but not free: a properly passivated 304 surface must be kept clean of carbon-steel tooling residue (free iron) before service, and field cutting/grinding debris has to be removed with dedicated stainless wire brushes, not the shop's general-purpose bench grinder. Skip that, and the buyer pays again at the first chloride exposure event.
Where to use stainless — and where to refuse the spec
Specify stainless where the failure cost of corrosion, contamination or wash-down downtime exceeds the material premium: food-processing conveyors, pharmaceutical fluid paths, marine hardware, architectural exterior cladding and any rolling-element bearing above 180°F [S3]. For abrasive, low-corrosion structural service (concrete-embedded rebar, indoor structural framing, general sheet metal), carbon steel or galvanised alternatives deliver the duty at a fraction of the cost.
For decorative exterior architectural panels where grain uniformity and colour repeatability matter more than corrosion margin, sandblasted 304 remains the workhorse, with the colour-match discipline flagged earlier as the recurring commercial risk [S1]. Next checkpoints to track: quarterly review of 304/316 spread pricing (Ni and Mo surcharges move the curve 5-15% between quarters), and any project-side update to the mill's 25 t coil MOQ policy for Q3-Q4 2026 allocation [S2].