304 vs 316 Stainless Steel: Which Grade Do You Actually Need?

The Two Most Common Stainless Grades

If you're specifying stainless steel for a fabricated or machined part, chances are you're choosing between 304 and 316. They're the two most widely used grades worldwide, and between them they cover the vast majority of applications.

304 is the default — the one you get if you just say "stainless steel" without specifying a grade. 316 is the upgrade, and it costs 20-40% more depending on market conditions. The question is whether that extra cost is actually buying you anything useful for your application. Often it isn't.

What's the Actual Difference?

Both 304 and 316 are austenitic stainless steels — part of the 300 series. They're non-magnetic (or very slightly magnetic after cold working), can't be hardened by heat treatment, and have excellent corrosion resistance compared to carbon steel.

304 (also called 18/8): Contains 18% chromium and 8% nickel. The chromium forms a thin, self-repairing oxide layer on the surface that prevents rusting. This is what makes stainless steel "stainless."

316: Contains 16% chromium, 10% nickel, and — here's the key part — 2% molybdenum. That molybdenum is what you're paying the premium for. It dramatically improves resistance to pitting and crevice corrosion caused by chlorides (salt, chlorine, and chloride-containing chemicals).

The 20-40% price premium on 316 comes from the higher nickel content and the molybdenum, both of which are expensive raw materials with volatile pricing.

Properties Comparison

Notice that the mechanical properties are essentially identical. 316 is not stronger than 304. It's not harder in any meaningful way for fabrication purposes. The only real difference is chloride corrosion resistance.

When 304 Is Perfectly Fine

304 stainless is more than adequate for a huge range of applications:

• Indoor fabrication — Enclosures, brackets, panels, frames, shelving
• Kitchen and food equipment — 304 is food-grade and used in commercial kitchens everywhere
• Freshwater exposure — Tanks, fittings, and components in contact with fresh water
• Architectural trim and cladding — Interior and non-coastal exterior applications
• General-purpose brackets and structural components not exposed to salt
• Mild chemical environments — Many dilute acids and alkalis at room temperature
• Medical instruments — Many surgical instruments are 304

If your part lives indoors, doesn't see salt, and isn't exposed to aggressive chemicals, 304 will serve you well for decades. Don't spend the extra 20-40% on 316 just because it sounds better.

When You Genuinely Need 316

316 earns its premium in environments where chlorides are present:

• Coastal and marine environments — If your part is within about 15km of the coast, salt spray will attack 304 over time. This is the most common reason to specify 316 in Australia.
• Swimming pool equipment — Chlorine is a chloride. Pool fences, fittings, ladders, and equipment need 316.
• Chemical processing — Acid tanks, chemical piping, reactor vessels. The molybdenum in 316 resists pitting from chloride-containing chemicals.
• Medical devices and pharmaceutical equipment — Cleaning chemicals used in pharmaceutical and medical sterilisation are harsh. 316 handles them better.
• Brewery and dairy equipment — CIP (clean-in-place) chemicals include caustic and acidic solutions that favour 316.
• Tropical and humid climates — High humidity combined with coastal proximity accelerates corrosion on 304.
• Underground or buried components — Soil conditions vary, but chloride-containing groundwater is common enough to warrant 316.

The rule of thumb is simple: if there's salt, chlorine, or aggressive chemicals involved, use 316. Otherwise, 304 is fine.

Fabrication Notes

Laser Cutting

Both grades cut well on a fibre laser with nitrogen assist gas — see our mild steel vs stainless steel laser cutting comparison for more on cutting characteristics. 316 is marginally harder, which means slightly higher laser power or slightly slower cutting speed for the same thickness. In practice the difference is small — maybe 5-10% slower. Both produce a clean, bright cut edge with nitrogen.

Welding

Both TIG weld beautifully — stainless TIG welding is almost therapeutic when the settings are right. Use matching filler rod: 308L filler for 304, 316L filler for 316. The "L" in the filler designation is important (see below).

Machining

Both grades work harden, which is the main challenge when machining stainless. Use sharp carbide tools, maintain steady cutting feeds (don't dwell or rub), and use appropriate cutting fluid. 316 is slightly gummier than 304 — it tends to form longer chips and can be more prone to built-up edge on the tool. Rigid setups and consistent feeds solve this.

Passivation

After fabrication — especially after welding, grinding, or machining — both grades benefit from passivation. This is a chemical treatment (usually nitric or citric acid) that removes surface contamination and restores the protective chromium oxide layer. It's not always mandatory, but it's good practice, especially for parts in corrosive environments.

Surface Finishes

Both grades are available in the same range of finishes: 2B (standard mill finish), No.4 (brushed/satin — the most common architectural finish), mirror polish, bead blast, and electropolish. The finish you choose is independent of the grade.

The L Grades: 304L and 316L

You'll often see 304L and 316L specified instead of plain 304 and 316. The "L" stands for low carbon — 0.03% maximum carbon content, compared to 0.08% for the standard grades.

Why does this matter? During welding, the heat-affected zone can reach temperatures (450-850°C) where chromium combines with carbon to form chromium carbides. These precipitate at the grain boundaries, depleting the surrounding metal of chromium — a process called sensitisation. The chromium-depleted zones then lose their corrosion resistance, leading to intergranular corrosion.

The low-carbon L grades resist sensitisation because there's simply not enough carbon available to form significant carbides. For any welded fabrication, always specify L grades (304L or 316L). Most Australian suppliers stock L grades as standard now, so there's rarely a price difference.

Common Mistakes

A few things we see regularly that cost people time and money:

• Using 304 near the coast — The classic mistake. 304 develops "tea staining" — brown rust spots — within months in coastal environments. It won't fail structurally, but it looks terrible and progressively worsens. If it's near salt water, use 316.

• Specifying 316 for an indoor bracket — The opposite mistake. If the part lives in a dry, indoor environment, 316 is a waste of money. 304 will last indefinitely indoors.

• Using carbon steel fasteners on stainless — Galvanic corrosion will attack the carbon steel fastener, and the rust will stain the stainless. Always use stainless fasteners on stainless components. Match the grade where possible (304 fasteners on 304, 316 on 316).

• Grinding with contaminated wheels or tools — If you use a grinding disc or wire wheel that's previously been used on carbon steel, tiny carbon steel particles embed in the stainless surface and rust. Keep your stainless tools separate from your carbon steel tools. This is a common cause of "mysterious" rust spots on brand-new stainless fabrications.

The Bottom Line

304 and 316 are both excellent materials. The choice between them comes down to one question: will the part be exposed to chlorides (salt, chlorine, or chloride-containing chemicals)?

If yes, use 316. If no, save your money and use 304.

Get Your Stainless Parts Made

We laser cut and fabricate both 304 and 316 stainless steel. Upload your DXF or STEP file to our instant sheet metal quoting tool for immediate pricing, or contact us for custom fabrication quotes. Compare stainless with other metals in our Material Comparison Tool, or estimate part weight with our Material Weight Calculator. For a deeper dive into stainless steel properties and applications, visit our stainless steel material guide. Not sure which grade you need? Give us a call on 07 5616 4988 and we'll help you choose.