What Pros Use to Prevent Screws from Rusting

For 28 years building coastal structures, we've watched contractors waste money on ‘outdoor’ screws that start showing red rust within months in salt air, then scramble to fix warranty callbacks when boards start pulling loose.

The truth: you can't prevent rust by coating screws after installation. You prevent rust by choosing the right screw material before you drive the first fastener.

This guide gives you what screws you should use outdoors based on your climate, wood type, and exposure conditions.

TL;DR: How to Prevent Rust on Outdoor Screws

• The best way to prevent rust on screws is using stainless steel screws, HDG screws, or coated screws.
• The best type of screws that don’t rust outside are stainless steel screws from Eagle Claw.
• Match your location and budget to the corrosion resistant screw you’re choosing.
• Use 316 near salt, chemicals, treated lumber, and tannin‑rich woods; use 304 for dry inland softwoods.
• DIY way to make screws rust proof: Use sealants and protectants as short‑term helpers only: marine‑grade polyurethane or silicone around heads, plus products like Boeshield T‑9, Fluid Film, or paste wax on exposed heads.
• Apply EPDM rubber washers under pan or hex heads in direct rain, and use butyl behind brackets to block moisture paths.
• The coatings to stop screws from rusting need upkeep and do not change the base metal; plan refastening if about 25% of screws show rust.

What type of screws don't rust outside?

Only stainless steel and screws with thick galvanized coatings are the types of screws that don’t rust outside.

Stainless steel screws (304 and 316 grades) work best because they have a chromium oxide layer that heals itself when scratched, making them true rust‑resistant wood screws. Eagle Claw offers the best stainless steel wood screws in both grades so you can match the spec to your project and budget.

Everything else (zinc-coated, black oxide, ceramic, epoxy, or polymer coatings) relies on a barrier coating that eventually wears off, chips during installation, or breaks down from sun exposure. Once that coating fails, screws start to rust.

Best Corrosion Resistant Screws That Actually Last

1. 304 stainless steel (corrosion resistant screws).

304 SS wood screws are good for inland builds where you get rain and snow but no salt spray. These rust resistant wood screws handle normal weather fine but pit out fast if you're near the ocean, have pool chemicals splashing on it, or use road salt nearby.

2. 316 stainless steel (best rust proof screws).

316 SS is marine grade with molybdenum added, which stops salt from eating through it. If you're coastal (within 5 miles of ocean), building a pool deck, or anywhere in Florida's humidity, these are the rustproof screws you need. Lasts 25+ years in direct salt spray. 316 stainless steel wood screws are the best rust proof screws and the only screws that don't rust in salt water.

3. Ceramic, epoxy, or polymer coated screws (budget weatherproof outdoor screws).

Coated screws are carbon steel with a thick applied coating (ceramic is most common). They’re marketed as "1000 hour salt spray tested" or "advanced corrosion protection."

Treat salt‑spray hours as a lab comparison, not a calendar. The coating can chip during installation if you hit knots or overdrive the screw, exposing bare steel that rusts. These are decent corrosion‑resistant deck screws for moderate climates

4. Hot-dip galvanized (50+ micron zinc coating).

You basically never find these in deck screw sizes. They're for structural bolts, lag screws, and joist hangers. If you see "galvanized" deck screws at a big-box store, it's almost always thin electroplated zinc (5–8 microns), not hot-dip. Ask for the coating thickness spec if you're not sure.

Now that you know which screw types resist rust, here's how to match them to your specific project.

What screws should I use for outdoors?

The screw you should use for outdoors depends on three things: where you're building (climate, distance from ocean), what wood you're using (treated vs untreated, species), and how long you want it to last.

Here's how to match your exact situation to know what screws you should use outside:

Near salt, chlorine, or pollution

• If you're within 5 miles of the ocean or can see/smell/taste salt in the air, use 316 stainless. 304 stains and pits in coastal air; 316 handles chlorides better.
• If you’ve got a pool, hot tub, or de‑icing salt around, use 316. Chlorides chew up coatings and will find any nick in a coated wood screw.
• If you're in industrial areas (factory smokestacks, industrial fumes, major city smog), use 316 stainless. Pollution speeds up corrosion and burns through thin zinc/coatings faster.

Wood, composites, and treatments

• If you're building with pressure-treated lumber (ACQ, CA-B, or Micro CA stamps), use stainless steel wood screws.
• If you're using cedar, redwood, white oak, red oak, ipe, or garapa, use 316. 304 can tea‑stain in wet, salty air, and 316 cuts the staining risk.
• If you're building composite or PVC decks (Trex, TimberTech, Azek), use 316 stainless even inland. Rust stains are permanent on composite and destroy $4-$8/sq ft material.
• If you're building raised garden beds with screws in soil, use 316 stainless. Soil moisture stays at 100% humidity, plus fertilizers speed up corrosion on carbon steel.
• If your wood is fire-retardant treated (FR or FRTW stamps), use stainless steel wood screws. Treatment plus wetting can corrode zinc/coated fasteners faster than you expect.

Design, metals, and drainage

• If you see big temperature swings (hot days/cold nights or freeze–thaw), use 316 stainless fasteners and keep water moving with slope and gaps. Temperature swings and freeze–thaw can stress coatings and joints when moisture gets in, so don’t rely on a thin barrier to stop rust on screws.
• If you’re fastening steel into aluminum (railings, trims), use 316 SS wood screws and isolate with nylon/plastic washers or bushings so the metals don’t touch. Stainless against aluminum will galvanically attack the aluminum in wet/salty air if you don’t isolate it.
• If you’ve got poor drainage (flat surfaces, tight board gaps, enclosed bases), use 316 SS wood screws and fix the detailing. Trapped water around heads and in joints drives crevice corrosion even on stainless.

Safety, traffic, and public spaces

• If you're building outdoor stairs or railings where failure means injury, use 316 stainless near salwater. Rusted screws create safety hazards when screws lose grip over time.
• If you see heavy foot traffic (decks, walkways, docks, patios), use 304 or 316 SS wood screws. Sand and furniture scrape coatings off carbon‑steel screws, SS wood screws keep its protection after scuffs.
• If it’s for public use (playgrounds, park benches, picnic tables), spec 316 stainless in salty or harsh air so inspectors aren’t flagging rusted hardware later.

Compliance and warranties

• If you're doing commercial decks with warranty requirements, use 316 stainless and document it. Many warranties require corrosion-resistant fasteners with specific ASTM ratings.

Water exposure and marine builds

• If you're building docks or piers in freshwater, run 316 for parts that stay wet or submerged and 304 SS screws for hardware above the splash zone. For saltwater docks and piers, only use 316 SS wood fasteners.

Furniture, storage, and budget inland

• If you're building high‑end furniture (teak, ipe, white oak), use stainless steel wood screws.
• If you store furniture indoors for winter, 304 stainless is fine. Drying breaks the wet–dry cycles that speed up corrosion outside.
• If you’re 10+ miles inland with dry seasons and using pine/fir/spruce, go 304 to save money. 316 typically costs around 40% more, so 304 is the value pick away from chlorides.

Choosing the right screw is 90% of rust prevention. The other 10%? How you install them and design your structure.

How to keep outdoor screws from rusting?

Choose the right material before installation. If you already installed zinc or black screws, coatings buy time but don't fix the problem.

Design for drainage

Water sitting against fasteners accelerates corrosion even on the best rustproof screws. We’ve built hundreds of timber constructures, and we've seen more fastener failures from poor drainage than any other cause.

Here's how to keep water moving so it doesn't pool around your screws.

Slope and spacing to stop screws from rusting

• Slope everything 1/8" per foot. Water needs somewhere to go. Deck boards should pitch away from the house. Fence caps and pergola beams need the same slight fall so rain sheds instead of pooling.
• Space boards 1/8" apart. Boards butted tight together trap water right where your screws sit. Use a 16-penny nail as a spacer when you're installing, then pull it out. That gap lets water drain through and air circulate.

Drainage holes to prevent rust on screws

• Drill weep holes at low points. Building planter boxes or post bases? Water gets trapped at the bottom with nowhere to go. Drill 3/8" holes at the lowest spots so water escapes instead of soaking your fasteners 24/7.
• Put joist tape on your framing first. Before you drive screws, seal the tops of your joists with waterproof tape (SPAX Deck Joist Tape or Trex Protect work great). It stops water from wicking down screw holes into the wood underneath, which can add 10 years to your deck's life.

Sealing rust to stop it from spreading

• Use rubber washers under screw heads. If you're using pan-head or hex-head screws on fences, railings, or siding that see direct rain, EPDM rubber washers create a watertight seal. Don't try this with bugle-head deck screws, they'll crush the wood.
• Countersink and seal bugle-heads on exposed spots. Drive your screws slightly below the surface and add a small ring of marine-grade sealant (polyurethane or silicone) around the head. Keeps water from pooling in that little depression.
• Run butyl tape under metal brackets. Before you mount joist hangers, post bases, or metal connectors, stick a thin bead of butyl tape where the metal meets wood. Water can't creep into the joint. Just don't use butyl under deck boards, it gets messy over time.

Plugs and caps to protect outdoor screws from rust

• Cover visible screws with plugs or caps. Building a nice fence or outdoor furniture? Countersink trim-head screws and cover them with matching wood plugs or plastic snap caps. Looks clean and keeps water out.
• Stop when screws are flush, don't bury them. Drive screws until heads sit even with the wood, then stop. Overdoing it cracks coatings on ceramic screws, splits wood fibers (which lets water in), and crushes sealing washers. Set your drill clutch to control depth automatically.

But what if you're standing at the hardware store staring at a box of screws? Here's how to verify they're actually rust proof.

How to tell if screws are rust proof?

You can tell if screws are rust proof by checking the box for 304 or 316, finding ASTM B117 or ISO 9227 on the spec without turning hours into years, and doing quick aisle checks like magnet pull, color, file feel, and head markings

Check certifications and ratings:

• Look for ASTM B117 salt spray ratings above 1,000 hours on the box or spec sheet. True rust proof screws hit 1,000+ hours. Ceramic and epoxy coated screws rate 500–1,000 hours. Anything under 500 hours rust in coastal or humid areas.
• Check for EN ISO 9227 certifications on European screws (UK and Australian manufacturers). Same test, same 1,000+ hour rule.
• Make sure the box says "304 stainless steel" or "316 stainless steel." Don't trust vague claims like "marine grade," "exterior grade," or "weather resistant." If "stainless steel" isn't spelled out with the grade number, assume it’s a coated carbon‑steel screw.

Run quick field tests:

• Magnet test: Most true 304/316 stainless won't stick to a magnet or has very weak attraction. Strong magnet pull = zinc‑plated steel or ferritic “stainless,” not 304/316.
• Color check: Zinc‑plated screws show a bright silver sheen with a slight blue tint. Gold/yellow screws are zinc chromate coated. True rustproof SS screws has duller, matte silver-gray appearance.
• File test: Rub the screw head with a metal file. Stainless resists filing; coated mild steel cuts easily.

When in doubt, ask for the spec sheet. Hardware store employees often can't distinguish between electroplated zinc and hot-dip galvanized, or 304 vs 316 stainless. Pull up the manufacturer's website on your phone or ask them to print the technical specs. Five minutes of research saves you from refastening your entire deck in three years.

Already installed the wrong screws and seeing rust? Here's what actually works when trying to fix it after the fact.

What can you put on screws to prevent rust?

Here's what homeowners ask about most when they've already installed the wrong screws and want to extend their life. We don't typically use these methods on projects we build because we use true corrosion resistant screws from the start.

Common DIY coatings to prevent rust on screws:

• Paste wax slows flash rust and adds a temporary moisture barrier. Expect weeks to a few months before you reapply, depending on exposure.
• Fluid Film is a lanolin‑based coating that stays wet and displaces moisture. Plan on reapplying about once a year on outdoor hardware.
• Boeshield T‑9 dries to a waxy film and is marketed for water‑resistant rust protection. Reapply as needed based on exposure and wear.
• 3‑in‑1 oil is a light mineral oil that protects short term. Rain and UV weathering break it down, so touch up often outdoors.
• Silicone sealant around screw heads can block water on small fixtures. It is not practical for decks with hundreds of screws
• Cold galvanizing spray is a zinc‑rich paint used for touch‑ups on galvanized steel. How well it prevents rust depends on surface prep and film build, and it can be messy or get chipped during installation

For screws already rusting:

• Clean with 0000-grade steel wool and WD-40, wipe clean, apply wax or Fluid Film immediately so the rust doesn’t return as fast.
• Replace any screw with deep pits or flaking around the joint to keep hardware reliable and to protect screws from future damage
• If a lot of fasteners (25%) show visible surface damage, stop doing spot fixes and schedule a full inspection and refastening plan for decks and stairs, since widespread issues are a safety warning in exposed locations.

How Pros Prevent Rusted Screws on Their Decks, Fences and Every Single Project

After installing hundreds of thousands of screws in commercial and residential projects, coating screws every year ends up costing more time and money than just using 316 stainless steel from the start.

These coatings work great if you're a homeowner buying time before replacement or maintaining small outdoor projects like furniture or gate hardware. But for decks, fences, or anything structural, we stick with proper stainless steel so we're not back fixing problems a few years later.

Stainless steel is the better move because it protects itself and does not rely on a coating that wears off. It cuts callbacks, labor, and long‑term costs. When you are ready to outfit a job, buy stainless steel deck screws in bulk from Eagle Claw with contractor pricing so crews get durable hardware without blowing the budget.