Nut Material Guide
Most nut types are available in several materials and finishes, and the right one comes down to three things: the corrosion environment, the strength you need, and cost. This guide compares the materials Eugene Fastener stocks — from everyday zinc-plated steel to silicon bronze for salt water — and gives a quick selection table so you can match the material to the job.
In This Guide:
- Quick Selection Table
- Steel (Zinc, Plain, Galvanized)
- 18-8 vs 316 Stainless
- Silicon Bronze
- Brass, Aluminum, Nylon
- Galvanic / Mixed-Metal Notes
- FAQ
Quick Selection Table
| Material | Corrosion Resistance | Relative Strength | Best For |
|---|---|---|---|
| Steel, Zinc Plated | Low-moderate (indoor) | High (by grade) | General indoor and light outdoor — the default |
| Steel, Hot-Dip Galvanized | Good (outdoor) | High | Outdoor, structural, treated lumber |
| 18-8 Stainless | Good | Moderate | Outdoor, food, washdown |
| 316 Stainless | Excellent (chloride) | Moderate | Marine and coastal, chemical |
| Silicon Bronze | Excellent (salt water) | Moderate | Marine, architectural, with bronze hardware |
| Brass | Good (not chloride) | Low | Electrical, decorative, non-magnetic |
| Aluminum | Good | Low | Lightweight, non-magnetic |
| Nylon | Excellent (inert) | Very low | Non-conductive, light-duty, anti-corrosion |
Steel: Zinc, Plain & Galvanized
Steel is the default for strength and value, and its corrosion resistance comes from the finish, not the base metal. Zinc-plated steel is the everyday choice for indoor and light outdoor use. Plain (uncoated) is used on oiled or painted assemblies and where a coating would interfere. Hot-dip galvanized adds a thick zinc layer for real outdoor and structural service, and is required with ACQ treated lumber. Steel nuts carry a grade (2, 5, 8, 9, or metric class) — see our Nut Grade & Bolt-Matching Guide.
18-8 vs 316 Stainless
18-8 stainless (the 300-series group that includes 304) resists rust well in general outdoor, food, and washdown environments and is non-magnetic. 316 stainless adds molybdenum, which dramatically improves resistance to chlorides — salt water, pool chemicals, and coastal air. Rule of thumb: 18-8 for general corrosion resistance, 316 when salt or chemicals are in play. Both have lower tensile strength than hardened steel and can gall during installation, so go slow and lubricate large sizes.
Silicon Bronze
Silicon bronze is the premium marine and architectural choice. It offers outstanding salt-water corrosion resistance, ages to an attractive patina, and — importantly — is galvanically compatible with bronze and many marine hardware metals, avoiding the dissimilar-metal corrosion you can get pairing stainless with bronze fittings. It is a specialty item; we drop-ship the full size range. See our Marine Fastener Material Guide for silicon bronze vs 316 vs brass in marine use.
Brass, Aluminum & Nylon
- Brass: corrosion-resistant (but not in chlorides), non-magnetic, and conductive — the choice for electrical, plumbing, and decorative work. Lower strength, not for structural loads.
- Aluminum: lightweight and non-magnetic, with good general corrosion resistance. Used where weight matters; low strength.
- Nylon: fully non-conductive, non-magnetic, and chemically inert. Excellent for electrical isolation and corrosion-proof light-duty work; very low load capacity and temperature limit.
Galvanic / Mixed-Metal Notes
When two dissimilar metals contact in a wet environment, the less-noble metal corrodes faster (galvanic corrosion). Best practice is to match the nut, bolt, and washer materials where you can. Pair stainless with stainless, bronze with bronze, and avoid putting a plain-steel nut on a stainless bolt in a wet setting. In marine work, silicon bronze and 316 are the safe families. When in doubt, ask us — we can spec a compatible set.
Frequently Asked Questions
What is the best nut material for outdoor use?
For general outdoor use, hot-dip galvanized steel or 18-8 stainless. For coastal or salt-water exposure, step up to 316 stainless or silicon bronze, which resist chloride corrosion that will eventually pit 18-8.
What is the difference between 18-8 and 316 stainless nuts?
Both resist rust, but 316 contains molybdenum that makes it far more resistant to chlorides (salt water, pool chemicals, de-icing salt). Use 18-8 for general corrosion resistance and 316 for marine and chemical environments.
Are stainless nuts stronger than steel nuts?
No. Standard 18-8 and 316 stainless have lower tensile strength than hardened Grade 5 or Grade 8 steel. Choose stainless for corrosion resistance, not strength; if you need both, ask about high-strength stainless or coated alloy options.
Why use silicon bronze instead of stainless on a boat?
Silicon bronze is galvanically compatible with bronze marine hardware and ages predictably in salt water, avoiding the dissimilar-metal corrosion that can occur when stainless contacts bronze fittings. It is the traditional choice for wooden-boat and architectural work; 316 stainless is the other marine-grade option.
Can I mix a stainless nut with a galvanized bolt?
It is best avoided in wet environments. Dissimilar metals can drive galvanic corrosion, and on structural assemblies the finishes are specified to match. Pair like with like where you can, or ask us to spec a compatible assembly.
Need Nuts in a Specific Material?
Eugene Fastener stocks nuts in zinc and plain steel, 18-8 and 316 stainless, brass, aluminum, and nylon, and drop-ships silicon bronze in the full range.