For sheet metal work, pick 316 for coastal and chemical exposure, 304 for food and general indoor-to-outdoor use, and 430 for dry indoor parts where cost matters more than corrosion resistance. The three grades look almost identical on a cut blank, but they behave very differently once bent, welded, and put into service. At Layer X we cut and press-brake all three from our Ahmedabad facility, and the wrong grade is one of the most expensive specification mistakes we see — because it rarely fails at inspection, it fails eighteen months later in the field.
This is the narrow version of the decision. If you are still choosing between mild steel, stainless, and aluminium as material families, start with our broader sheet metal material selection guide. This article assumes you have already settled on stainless and now need to choose the grade.
The three grades in one paragraph each
304 is the austenitic workhorse — the grade most people mean when they say "stainless". It contains chromium and nickel, resists most atmospheric and food-contact corrosion, welds cleanly, and forms without cracking. If a drawing simply says "stainless steel, food grade", it almost always means 304 (or its low-carbon variant 304L for welded assemblies).
316 is 304 with molybdenum added. That single addition dramatically improves resistance to chlorides — salt spray, coastal air, swimming-pool chemistry, de-icing salt, and many process fluids. It is often called "marine grade". It forms and welds much like 304 but costs noticeably more, so you specify it where the environment actually demands it, not as a blanket upgrade.
430 is a ferritic grade with chromium but effectively no nickel. Removing the nickel makes it cheaper and less prone to the wild price swings of the austenitic grades, and it is magnetic where 304 and 316 are largely non-magnetic. The trade-off: lower corrosion resistance, a tighter forming window, and poorer weldability. It is a decorative and dry-environment grade, not a structural marine one.
The chemistry behind these grades is codified in ASTM A240 (the standard specification for chromium and chromium-nickel stainless steel plate, sheet, and strip) and the European equivalent EN 10088-2. When you quote a job with us, name the grade against one of those standards and there is no ambiguity about what arrives.
Grade-by-environment picker
The fastest way to choose is to start from where the part lives, not from a datasheet. Here is how we route the three grades by service environment:
| Environment | Recommended grade | Why |
|---|---|---|
| Coastal / marine / salt exposure | 316 (316L if welded) | Molybdenum resists chloride pitting; 304 will show tea-staining and eventually pit within sight of the sea. |
| Chemical, pharma, high-chloride process fluids | 316 | Better resistance to aggressive cleaning agents and process media; the default for wash-down chemical plant. |
| Food processing, dairy, commercial kitchen | 304 (316 if brine/salt is involved) | 304 handles food contact and routine sanitising; upgrade to 316 only where salt, brine, or acidic products sit against the metal. |
| General outdoor, urban, non-coastal | 304 | Copes with rain and humidity in inland Gujarat conditions without the 316 cost premium. |
| Dry indoor — trim, panels, appliance skins | 430 | Corrosion resistance is not the driver; you are paying for a bright stainless look at the lowest grade cost. |
| Interior with condensation or occasional wet | 304 | 430 can rust in persistent damp or where the passive layer is scratched and never re-forms cleanly. |
Cost: what you actually pay for
The price ladder runs 430 (cheapest) then 304 then 316. The gap between 304 and 316 is driven almost entirely by molybdenum and higher nickel content; the gap between 430 and the austenitic grades is driven by 430 carrying essentially no nickel at all. Nickel is the volatile ingredient, so 430's price is also steadier over time — a real consideration on long production runs quoted months ahead.
The lazy cost mistake is to default every stainless part to 316 "to be safe". On an indoor electrical enclosure that never sees salt, that decision can add a meaningful percentage to material cost across a batch for zero service benefit. Equally, saving money with 430 on a coastal handrail is a false economy — you pay once in material and again in warranty replacement. Match the grade to the environment and the cost takes care of itself.
Formability: what happens at the press brake
This is where the grades diverge most on the shop floor, and it is the part datasheets under-explain.
- 304 and 316 are austenitic — ductile, tolerant of tight inside radii, and forgiving on multi-bend enclosures. They work-harden as you form them, so they spring back more than mild steel and need slightly more press force, but they bend reliably without cracking. Both suit the complex, multi-step bend sequences typical of chassis and cabinetry.
- 430 is ferritic and less ductile. It tolerates a simple bend but is more prone to cracking on tight radii and along the grain direction, so bend lines ideally run across the rolling direction and inside radii are kept generous. It is fine for a folded panel or a simple bracket; it fights you on a deep-drawn or heavily formed part.
Our CNC press brake holds ±0.3° on bend angle and handles material up to 8mm thick in stainless, with a maximum bend length of 3200mm and 160 tonnes of press force. For 430, we bias inside radii larger and orient bends against the grain to stay clear of cracking; for 304 and 316 we can hold tighter radii with confidence. Springback is compensated in the tooling setup for all three, and bent parts can be checked with a digital angle gauge and certified on request.
Cutting and welding notes
All three grades cut cleanly on our 3kW fibre laser, which handles stainless up to 12mm with a kerf of roughly 0.1–0.25mm and holds ±0.1mm on profile dimensions. The important detail for stainless is the assist gas: we cut it under high-pressure nitrogen rather than oxygen, so the cut edge stays bright and oxide-free instead of scaling — which matters for both appearance and corrosion resistance, since a scaled edge is a corrosion starting point. Our full fibre laser cutting service covers the cutting side of any sheet metal order.
On welding: 304 and 316 weld readily, and for welded assemblies the low-carbon L variants (304L, 316L) resist the grain-boundary carbide precipitation ("sensitisation") that can leave a weld zone vulnerable to corrosion. 430 is the awkward one — ferritic grades can suffer grain growth and reduced toughness in the heat-affected zone, so where a stainless part must be welded and stay corrosion-resistant, we steer clients to 304L or 316L rather than 430.
Surface finish and passivation
Stainless does not resist corrosion because of what it is coated with — it resists because chromium reacts with oxygen to form an invisible, self-healing passive layer. Anything that contaminates or interrupts that layer undermines the grade you paid for. The two most common culprits on a fabricated part are embedded iron (from steel tooling, a shared grinding wheel, or carbon-steel swarf) and heavy heat scale from cutting or welding.
That is why we cut stainless under nitrogen for a bright edge, keep stainless work separated from carbon-steel handling, and can passivate finished parts on request so the chromium-oxide film reforms clean across the whole surface. For a coastal 316 part especially, passivation is not cosmetic — it is what lets the molybdenum do its job. The grade on the drawing only delivers its rated corrosion resistance if the surface is clean when it leaves the door, and that discipline is as important to the outcome as the grade choice itself.
A quick word on grain and directionality
Sheet stainless has a rolling direction, and it matters for both forming and finish. Bends made across the grain crack less readily than bends along it — decisive for 430, useful margin for 304 and 316. Brushed or grained finishes also need consistent orientation across an assembly so panels match under light. When you send us a job, marking the preferred grain direction on the drawing lets us nest and bend to keep both the mechanics and the appearance consistent.
Common specification mistakes we correct
- 316 everywhere "to be safe". Pay for molybdenum only where chlorides are present. Indoors and inland, 304 is the right answer.
- 430 for a wet or coastal part. It will rust once the passive layer is compromised. Reserve 430 for dry, decorative, indoor work.
- Standard-carbon grade on a welded assembly. Specify 304L or 316L when the part is welded, to avoid sensitisation at the weld.
- Tight radii on 430. Ferritic stainless cracks where austenitic bends. Loosen the radius or move to 304.
- Assuming all stainless is non-magnetic. 430 is magnetic; if your assembly relies on non-magnetic behaviour, that alone rules it out.
How Layer X handles a stainless sheet metal order
We run a single-source workflow from our Satellite, Ahmedabad facility: your blank is laser-cut and then press-brake-bent in the same building, so it never leaves our hands between operations. That matters for stainless specifically — every extra handling step is a chance to scratch the surface and seed corrosion. We are ISO 9001:2015 certified, ship pan-India, and hold a 99.4% first-pass yield across the 2,000+ parts we have delivered, with grade certification available against ASTM A240 or EN 10088-2 on request. Our combined CNC sheet metal bending service is where these jobs are quoted and built.
If in doubt, tell us the environment the part lives in and we will recommend the grade — that conversation costs nothing and saves a field failure later.
Ready to quote a stainless sheet metal part? Upload your CAD file for a 24-hour quote — tell us the grade and service environment, and we will confirm formability and cutting before you commit.