Stainless Steel 304 vs 316: Which Is Better? All the Differences

Twenty-eight years of building structures with stainless fasteners teaches you what textbooks never cover. We've tracked installations from Pensacola to Portland, watched coastal decks age in real time, and documented which grades survive versus which ones pit out in 36 months.

The data doesn't lie. Match your fastener grade to your environment and use proper installation technique? You'll get decades of performance. Guess wrong or drive them incorrectly? Prepare for expensive callbacks.

This breakdown gives you the chemistry, real-world performance numbers, and costly mistakes we've seen contractors make repeatedly. No fluff. Just what actually matters when you're standing at the supplier counter trying to decide which box to buy.

TL;DR (SS 304 vs SS 316 Difference)

• The difference between 304 and 316 is mainly molybdenum. 304 contains essentially zero.
• 304 is the stronger grade at 660-671 MPa. 316 maxes out at 568-645 MPa. Neither matters, your lumber splits before either grade reaches its limit.
• 304 and 316 aren't harder than each other. Both measure 70-90 Rockwell B. Manufacturing methods make screws harder, not the grade difference.
• 316 has superior corrosion resistance to 304.
• 316 is more expensive than 304.
• 316 runs 30+ years near the ocean without the protective layer breaking down. 304 in saltwater locations results in rust pits that show up in 3 years because salt blocks the metal from healing itself.
• You can't tell which is 304 and 316 just by their appearance. Find a trusted SS screw supplier that labels their boxes.

What Is the Difference Between 304 and 316 Stainless Steel?

The difference between 304 and 316 is molybdenum. That's it.

316 alloy contains 2-3% molybdenum. 304 has essentially none. That single compositional difference controls how each metal responds to chloride ions, the corrosive agent in saltwater that eats through passive films and creates pitting.

304 and 316 are in the same austenitic stainless family. Same crystal structure. Non-magnetic. Easy to form and fabricate. They rely on chromium to build that protective oxide barrier. This barrier is the invisible nanometer-thick film that forms when chromium molecules react with atmospheric oxygen.

304 vs 316 Stainless Steel Chemical Composition

Now let's break down what these compositional differences actually mean for your project.

304 vs 316 Stainless Steel Strength: Which Is Stronger?

Which grade is stronger under tension? 304. Laboratory testing puts 304 at 660-671 MPa (95,700-97,300 psi) versus 316's 568-645 MPa (82,400-93,600 psi). Yield strength runs nearly identical. 304 averages 278 MPa, 316 sits at 258 MPa.

Does this matter for wood screws? Not even slightly.

That 7% gap means nothing when you're driving screws into wood.

Carbon steel coated fasteners actually deliver higher tensile strength (1000-1170 MPa), yet contractors don't see performance advantages because the limiting factor isn't the screw. Wood fiber splits or pulls through long before any of these metals approach their failure point. You could install 304, 316, or coated steel, and the lumber gives out first every single time.

What actually determines load capacity? Screw diameter and thread engagement depth. A #8 fastener holds less than a #14 structural screw regardless of metallurgy. Get the sizing right. Strength differences don't matter when both alloys exceed what wood construction demands.

304 vs 316 Stainless Steel Hardness: Which Is Harder?

Testing reveals that we get the same hardness from both grades. Fresh from the mill, expect 70-90 on the Rockwell B scale for either alloy. The chemical similarity between them (chromium, nickel, and iron making up the bulk composition) means their baseline hardness matches closely.

Manufacturing actually makes the steel harder. When you cold-form screws and roll threads, the metal work-hardens from all that pressing and shaping. The dies force threads into the shank and form the head. The crystal structure gets compressed, and the strength goes up.

Both 304 and 316 respond the same way. Tougher surface means threads grab wood better and don't wear out when you drive them.

Will you notice a hardness difference between 316 and 304 stainless wood screws? No. The manufacturing process matters more than the grade when it comes to installed performance. 

Just make sure you’re buying deck screws that are made using the right manufacturing process. The top deck screws are made in Taiwan. GRK, DeckPlus and Eagle Claw Fasteners, the brands that are most trusted by deck builders, are all made in Taiwan.

304 vs 316 Stainless Steel Corrosion Resistance: Which Is More Corrosion Resistant?

This is where molybdenum earns its keep. Adding 2-3% measurably improves pitting resistance in salt environments, validated through decades of field observations and controlled laboratory testing.

Building in coastal Florida, California, along UK shorelines, or Australian beaches? This chemical difference determines whether your fasteners survive 30 years or fail in three.

Salt destroys stainless steel in a specific way. Here's the breakdown.

Chromium bonds with oxygen and forms a super-thin protective film across the metal surface. This film fixes itself automatically if you scratch it. Fresh chromium atoms rush to the damaged spot and grab oxygen molecules. No film? The steel rusts fast.

Salt spray changes everything. Chloride ions punch holes through that protection and stop the chromium from rebuilding, and then tiny pits form. Those pits create their own little corrosive environments that eat deeper into the metal while the rest of the surface looks fine. Once pitting starts, it accelerates until the fastener fails.

So how do these grades handle salt attack differently?

304 can't rebuild its protective film once chlorides break it down. The chromium keeps trying to form new oxide, but salt blocks it faster than the metal heals. Pitting takes over. Structural failure follows.

316's has molybdenum as an added defense. That element creates molybdate ions that keep the protective film stable even when salt is present. The layer stays intact and keeps healing itself. The film never fully breaks down, so pitting never gets started.

That's why 316 survives coastal environments and 304 doesn't.

304 vs 316 Stainless Steel Cost: Which Is More Expensive?

Expect marine grade 316 to run 20-30% more than 304 for equivalent fasteners and raw material. There are three reasons why 316 SS costs more:

Molybdenum content adds direct material expense tied to commodity markets. That 2-3% alloying element costs significantly more per pound than base iron or chromium.

Extra nickel increases the price tag. 316 contains 2-4% more nickel than 304, and when nickel markets spike (which happens cyclically), that gap widens.

Tougher manufacturing pushes production costs higher. 316 work-hardens more aggressively during cold heading and thread rolling, requiring more force, slower speeds, and faster tool wear. Manufacturers pass these costs through to end users.

Commodity market fluctuations mean the exact premium varies month to month, but 316 consistently costs more.

304 And 316 Stainless Steel Price Comparison

Our 316 runs about 30% more than 304, yet still prices 40-50% below premium brands for comparable quality.

Stainless Steel 304 vs 316: Which Holds Up Better?

Wondering if 304 stainless is good enough for saltwater, or if you really need to spend extra for 316? Let me save you from an expensive mistake: buy marine grade for coastal work.

316 survives coastal environments for decades. 304 screws develop rust pitting within 36 months near saltwater. We've watched this pattern repeat across hundreds of installations, and the timeline never changes.

Your distance from the ocean makes all the difference.

Will 304 Stainless Steel Rust in Salt Water?

Yes. 304 will rust in saltwater and coastal environments. Salt air doesn't stop at the beach. The Galvanizers Association tracked atmospheric corrosion rates to map exactly where damage occurs.

0-5 miles from coast (0-8km): Danger zone. Every onshore wind event carries salt particles directly into your structure. You're working in a constant corrosive mist. Use 316 exclusively.

5-10 miles inland (8-16km): Still classified as coastal per the International Molybdenum Association. Salt particles travel farther than most people expect, maintaining high enough concentrations to attack 304's passive film. Use 316 SS through this range.

30-50 miles inland (48-80km): Corrosion rates drop significantly. Atmospheric salt concentration decreases enough that 304 becomes viable. You're dealing with normal atmospheric conditions rather than marine attack. Save the money and run standard grade.

Between 10-30 miles? Use your judgment based on prevailing wind patterns, elevation, and local geography. When in doubt, go marine grade.

304 vs 316 Stainless Steel Appearance: How to Check SS 304 and 316?

You cannot tell 304 from 316 by looking at them. Identical finish. Same shine. Matching surface characteristics. The only difference lives in the chemical composition, and you need testing to verify that.

How to Tell 304 From 316 Stainless Steel

Contractors have limited options for distinguishing these grades. Most methods require specialized equipment or professional testing. Here's what works without a full lab:

Check manufacturer markings first (most reliable method):

Look for stamped grades on screw heads or shanks. Ask your supplier for mill test reports and certifications. Verify packaging labels match what's actually inside the box.

Eagle Claw stamps every box with exact specifications because we've watched too many projects fail from unmarked hardware. Contractors who guess at material grades pay for it later. This remains the only reliable verification method without buying test equipment.

Magnet test (confirms stainless, won't identify the grade):

Magnets don't grab 304 or 316 in annealed form. Austenitic stainless stays non-magnetic.

Here's what the magnet actually tells you:

• Magnet grabs it: You've got ferritic steel or carbon steel. Not stainless.
• Magnet won't stick: It's austenitic stainless. Could be 304, 316, or something else entirely. Test proves nothing about grade.

IMPORTANT: Cold-worked screws grab magnets weakly. Thread rolling deforms the crystal structure enough to create trace magnetism in both 304 and 316. Doesn't tell you which grade you've got.

The test only verifies stainless but provides zero grade identification.

Tests requiring equipment or professional services:

Molybdenum spot test (requires purchasing kit):

Chemical test kits use acidic reagents that produce color reactions based on molybdenum presence:

• Red color that remains: Indicates 316 or another molybdenum-bearing grade
• Red color disappears immediately: Suggests 304 without molybdenum
• Black color that remains: Indicates inferior SS 202 grade

You'll need the kit ($50-150), must scratch or grind the material to expose fresh metal, apply reagent, then compare color changes to reference charts. Accuracy ranges 80-90% when performed correctly, but requires practice for reliable results.

XRF spectroscopy (requires hiring testing service):

X-Ray Fluorescence provides greater than 99% accuracy for stainless steel identification. Professional metal analysis services use handheld XRF analyzers that determine elemental composition in seconds:

• Measures X-ray emissions from samples to identify all major alloying elements
• Detects molybdenum presence conclusively (2-3% in 316, 0% in 304)
• Non-destructive testing that doesn't damage the material
• Results in seconds without lab delays

Can't verify the grade? Always assume the worst. If fasteners lack clear markings and you're building anywhere near the coast in Florida, California, Australia, or the UK, treat that mystery metal as 304 and order certified 316 instead.

Where To Buy TRUE 304 And 316 Stainless Steel Screws For Timber Construction?

Eagle Claw Fasteners sells verified SS 304 and SS 316 screws with clear grade labeling on every box.

We've sold tens of millions of fasteners and built our reputation on transparency. After watching contractors deal with stripped heads, unmarked grades, and rust stains appearing 24 months into coastal projects, we started manufacturing fasteners the way they should be made from day one.

Business customers (contractors, deck builders, fencers) get 10% off every order through our contractor program. We ship to the US, Canada, Australia, and the UK, with bulk pricing for large coastal projects. Never buy unmarked stainless steel fasteners. Get screws you can actually verify.

FAQs

Why Do Stainless Steel Screws Strip?

Stainless steel screws strip because of worn-out bits, improper driving technique, and using Phillips heads instead of Torx.

Worn bits lose their edge after hundreds of screws. The recess rounds out, your bit can't grab anymore, slippage happens, then the screw head gets destroyed.

Over-tightening wears down the drive recess even on fresh screws. Too much torque means the bit spins out. Damage done.

Phillips screws are designed to cam out. The angled sides push your bit upward when you apply torque. Factory assembly lines use this feature to prevent over-tightening, but it destroys fasteners during deck building.

That's why we use Torx. Vertical walls keep the bit locked in. No cam-out. No stripping. Our crews switched to Torx exclusively years ago.

Do I Need to Pre-Drill Stainless Steel Screws?

Yes, you need to pre-drill stainless steel screws to prevent stripping and board splitting.

Pre-drilling reduces resistance in dense hardwoods like Ipe or Cumaru. Without a pilot hole, your bit slips, your screw bends, or your board splits. Drill a clearance hole in the deck board and a pilot hole in the joist. Takes 30 seconds per screw. Saves you from replacing stripped fasteners and cracked boards.

What are the Best Stainless Steel Deck Screws?

Eagle Claw offers the best value stainless steel deck screws for contractors and DIYers.

Made by contractors for contractors, our fasteners feature Torx drive heads that prevent stripping. Professional-grade quality without the markup. They drive clean, hold strong, and don't strip out like cheaper Phillips head screws.