304 vs 316 Stainless Steel: The Complete UK Grade Guide
304 and 316 are the two most widely used stainless steels in the UK, and choosing between them comes down to one thing above all: how corrosive the environment is. This guide explains the real difference between 304 and 316 stainless steel - composition, corrosion and pitting resistance, cost, magnetism and the low-carbon 304L/316L welding grades - and gives a simple grade recommender so you can pick the right one for your project. Figures are to BS EN 10088, the European standard for stainless steels.
Which Grade Do I Need?
Pick the closest environment for an indicative recommendation. For critical or safety-related applications, confirm with a corrosion engineer.
What Is 304 Stainless Steel?
304 (EN designation 1.4301, or 1.4307 for the low-carbon 304L) is the most widely used austenitic stainless steel. It contains around 18% chromium and 8% nickel and no molybdenum. It offers excellent corrosion resistance in most everyday environments, is easy to form, weld and fabricate, and has a clean bright finish - which is why it dominates architectural, food, catering and general fabrication work.
What Is 316 Stainless Steel?
316 (EN designation 1.4401, or 1.4404 for the low-carbon 316L) is often called marine grade stainless. Its chemistry is similar to 304 but with 2 to 2.5% molybdenum added, plus a little more nickel. That molybdenum dramatically improves resistance to chloride-induced pitting and crevice corrosion, making 316 the grade for coastal, marine, pool and chemical environments.
304 vs 316: Composition Compared
Typical composition to BS EN 10088-1:
| Element | 304 (1.4301) | 316 (1.4401) |
| Chromium (Cr) | 17.5 - 19.5% | 16.5 - 18.5% |
| Nickel (Ni) | 8.0 - 10.5% | 10.0 - 13.0% |
| Molybdenum (Mo) | None (residual only) | 2.0 - 2.5% |
| Carbon (C) max | 0.07% (304L: 0.030%) | 0.07% (316L: 0.030%) |
| PREN (approx) | 18 - 20 | 24 - 26 |
PREN (Pitting Resistance Equivalent Number = %Cr + 3.3 x %Mo + 16 x %N) is the standard measure of resistance to chloride pitting - the higher the better. The molybdenum in 316 lifts its PREN well above 304, which is the whole reason 316 is specified near salt.
The Key Differences
Corrosion resistance
Both grades resist general corrosion excellently. The difference shows up with chlorides (salt): 304 can suffer pitting and crevice corrosion in coastal, marine and chlorinated conditions, whereas 316's molybdenum gives it much greater resistance in exactly those environments.
Cost
316 is more expensive than 304 - typically in the region of 10 to 30% more depending on product form and current nickel and molybdenum prices - because molybdenum and the extra nickel are costly alloying elements. For non-marine uses, paying the 316 premium usually isn't necessary.
Strength & workability
The two grades have very similar mechanical properties, and both are readily welded, machined and formed. There is no meaningful strength advantage in choosing one over the other - the decision is about corrosion, not load.
Magnetism
Both 304 and 316 are austenitic and are essentially non-magnetic in the annealed condition. Cold working (bending, rolling, drawing) can induce slight magnetism, especially in 304. A strong magnet test does not reliably distinguish 304 from 316.
304L and 316L: The Welding Grades
The "L" grades (304L / 1.4307 and 316L / 1.4404) are low-carbon versions. Keeping carbon below 0.030% avoids carbide precipitation (sensitisation) in the heat-affected zone during welding, which would otherwise reduce corrosion resistance at the weld - so specify the L grade for welded fabrications, particularly in thicker sections or corrosive service.
When to Choose 304 vs 316
Choose 304 for indoor and general outdoor use, architectural metalwork, balustrades and handrails inland, catering and food-prep equipment, brackets, frames and most fabrication - it is the economical workhorse and covers the majority of UK applications.
Choose 316 for coastal and marine locations, saltwater exposure, swimming pools and spas, chemical and heavy-industrial plant, and anywhere subject to road de-icing salt. When in doubt near the sea, 316 is the safe specification.
Stainless Steel vs Galvanised Steel
If you're weighing stainless against a cheaper option, galvanised steel gives good outdoor corrosion resistance at lower cost but eventually the zinc is consumed and the steel rusts. Stainless resists corrosion for the life of the part. See our galvanised steel guide for how the two compare.
Buy 304 & 316 Stainless Steel at Rackerman
Rackerman supplies UK-stock stainless steel, cut to size on request, with fast delivery:
- Stainless round tube - 304 & 316, satin & mirror (the 42.4/48.3mm handrail sizes come in 316 for marine use)
- Stainless steel sheet - 304 2B
- Stainless box & rectangle section
- 304 stainless equal angle
- 304 stainless square bar and round bar
Work out the weight of any stainless section with our metal weight calculator.
Frequently Asked Questions
What is the main difference between 304 and 316 stainless steel?
316 contains 2 to 2.5% molybdenum, which 304 does not. Molybdenum greatly improves resistance to chloride (salt) pitting corrosion, making 316 the choice for marine, coastal, pool and chemical environments. Otherwise the two grades are very similar.
Is 316 stainless steel worth the extra cost?
Only where chlorides are present. Near the sea, in pools, or in chemical plant, 316 is worth the 10 to 30% premium. For indoor and general inland use, 304 performs just as well for less.
Is 304 or 316 stainless magnetic?
Both are essentially non-magnetic in the annealed state, as both are austenitic. Cold working can induce slight magnetism, so a magnet is not a reliable way to tell the grades apart.
What does the L mean in 304L and 316L?
L stands for low carbon (maximum 0.030%). Low-carbon grades resist carbide precipitation (sensitisation) during welding, preserving corrosion resistance at the weld. Specify 304L or 316L for welded fabrications.
Which stainless steel is best for coastal or marine use?
316 (or 316L for welded parts). Its molybdenum content resists the chloride pitting caused by salt air and seawater far better than 304.
What are the EN grade numbers for 304 and 316?
Under BS EN 10088, 304 is 1.4301 (304L is 1.4307) and 316 is 1.4401 (316L is 1.4404). These are the designations you'll see on mill certificates.