304 vs 316 Stainless Steel: How to Choose the Right Grade

304 and 316: The Two Workhorses of Stainless Steel

Type 304 and Type 316 are austenitic stainless steels, the class defined by a face-centred cubic structure that gives excellent formability, weldability and toughness. Between them they account for the large majority of stainless steel used worldwide. Both are covered by ASTM A240 for plate, sheet and strip, and by a wide family of pipe, tube and bar specifications. The practical question for buyers and engineers is simple: when is the extra cost of 316 justified?

Chemical Composition per ASTM A240

The decisive difference is molybdenum. Type 304 contains 18.0-20.0 % chromium and 8.0-10.5 % nickel; Type 316 contains 16.0-18.0 % chromium, 10.0-14.0 % nickel and 2.0-3.0 % molybdenum. Molybdenum is the element that resists attack by chlorides, and it is the reason 316 outperforms 304 in saltwater, de-icing salt and many industrial chemicals.

Element	304 (UNS S30400)	316 (UNS S31600)
Chromium	18.0-20.0	16.0-18.0
Nickel	8.0-10.5	10.0-14.0
Molybdenum	-	2.0-3.0
Carbon	0.08 max	0.08 max
Manganese	2.00 max	2.00 max
Silicon	0.75 max	0.75 max

In addition to molybdenum, 316 carries slightly higher nickel, which adds to its toughness and stability. Low-carbon variants 304L and 316L (carbon 0.03 % maximum) are preferred for welded construction to avoid sensitisation.

Mechanical Properties and High-Temperature Limits

Per ASTM A240, both grades must meet minimum tensile strength of 515 MPa and yield strength of 205 MPa in the annealed condition, with elongation of at least 40 %. In everyday fabrication there is no meaningful strength difference; the choice is driven by corrosion and cost.

Property	304	316
Tensile strength	515 MPa min	515 MPa min
Yield strength (0.2 % offset)	205 MPa min	205 MPa min
Elongation in 50 mm	40 % min	40 % min

Both grades tolerate elevated temperatures, but 316 holds its properties longer in continuous high-heat service, remaining stable up to about 870 °C, where 304 begins to scale and lose strength more quickly. For sustained service above 800 °C, however, stabilised grades such as 321 or 347, or high-alloy grades such as 310, are better choices than either 304 or 316.

Corrosion Resistance: The Molybdenum Effect

Type 304 resists atmospheric corrosion, fresh water, foodstuffs, most organic chemicals and many mild industrial media. It is the standard material for kitchen equipment, architectural trim, indoor handrails and general process equipment in dry or mildly corrosive environments. Type 316 excels where chlorides are present: saltwater and coastal atmospheres, marine hardware, chemical processing, pulp and paper, pharmaceutical plants and food processing with aggressive cleaning chemicals. The molybdenum raises resistance to pitting and crevice corrosion, the two failure modes that chlorides cause in 304. For severe seawater duty, however, even 316 may be insufficient, and duplex or super-austenitic grades should be evaluated.

Cost and Fabrication

Because of the molybdenum addition and higher nickel content, 316 typically costs 20-30 % more than 304 at the material level. The price premium is usually worth paying where corrosion failure would be expensive, but it is wasted in benign environments where 304 performs identically. On fabrication, 304 is slightly more ductile and easier to weld and form, while 316 remains fully workable but benefits from more careful welding technique, particularly control of heat input, to preserve its corrosion resistance at the weld. Both grades are non-magnetic in the annealed condition and both can be machined, though the tougher 316 takes slightly longer.

FAQ

Q1. How do the compositions of 304 and 316 differ? 304 has 18-20 % chromium and 8-10.5 % nickel; 316 has 16-18 % chromium, 10-14 % nickel and 2-3 % molybdenum. The molybdenum is what gives 316 its chloride resistance.

Q2. When should I pay extra for 316? Choose 316 for saltwater, coastal or marine exposure, chlorides, and demanding chemical or pharmaceutical environments. Choose 304 for indoor, dry or mildly corrosive applications where its performance is identical at lower cost.

Q3. How large is the cost difference? 316 is typically 20-30 % more expensive than 304 because of molybdenum and higher nickel content.

Q4. Which grade handles high temperatures better? 316 remains stable up to about 870 °C in continuous service, outperforming 304 in prolonged high-heat industrial duty. Above 800 °C, consider stabilised or high-alloy grades instead.

Q5. Is 304 easier to fabricate than 316? Slightly. 304 is more ductile and a little easier to weld and form. 316 is fully workable but needs more controlled welding heat input to keep its corrosion resistance at the joint.