Fastener Material Comparison Chart

Material & Finish GuideMATERIALS · FINISHES
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Reference only. Material properties per ASTM, SAE and ISO standards. Corrosion ratings are general guidance. Verify critical applications with material certifications and an engineer. © Mutual Screw & Supply. Printed from mutualscrew.com/pages/fastener-material-finish-guide

How to choose the right fastener material and finish. Compare carbon steel, stainless grades, bronze, brass and nylon, see how zinc, galvanized and other coatings hold up, and find the best fastener for every environment.

Fastener Base Materials Compared

Base material determines fundamental strength, corrosion behavior, weight and cost. Coatings and finishes can extend the life of carbon steel in corrosive environments, but for severe or permanent exposure, start with the right base material. Ratings are relative on a 1 to 5 scale. For cost, more dots means more expensive.

Low Carbon Steel

SAE 1006–1022 · Grade 2 / Class 4.6
Tensile strengthTensile strength: 2 of 5
Corrosion resistanceCorrosion resistance: 1 of 5
WeldabilityWeldability: 5 of 5
CostCost: 1 of 5

General purpose. Most economical option. Requires coating for any outdoor or moisture exposure. Common for anchors, wood screws, sheet metal screws, and light machine screws.

Shop Grade 2 hex cap screws →

Medium Carbon Steel

SAE 1030–1045 · Grade 5 / Class 8.8
Tensile strengthTensile strength: 3 of 5
Corrosion resistanceCorrosion resistance: 1 of 5
WeldabilityWeldability: 3 of 5
CostCost: 2 of 5

Standard structural bolt material. Quenched and tempered for Grade 5 / 8.8 and above. Most automotive and machinery bolts. Requires coating outdoors.

Shop Grade 5 hex cap screws →

Medium Carbon Alloy Steel

SAE 4037–4340 · Grade 8 / Class 10.9–12.9
Tensile strengthTensile strength: 4 of 5
Corrosion resistanceCorrosion resistance: 1 of 5
WeldabilityWeldability: 2 of 5
CostCost: 3 of 5

High-strength bolts. Chromium, molybdenum, or nickel additions increase hardenability. Suspension bolts, drivetrain hardware, heavy equipment. Not for galvanizing at Grade 8+.

Shop Grade 8 hex cap screws →

18-8 Stainless Steel

AISI 304 · A2-70 · Most common SS
Tensile strengthTensile strength: 3 of 5
Corrosion resistanceCorrosion resistance: 4 of 5
WeldabilityWeldability: 4 of 5
CostCost: 3 of 5

Most common stainless grade. Excellent general corrosion resistance. Food service, outdoor hardware, pharmaceutical, light marine. Not for chloride-heavy environments.

Shop 18-8 stainless machine screws →

316 Stainless Steel

AISI 316 · A4-70/80 · Marine grade
Tensile strengthTensile strength: 3 of 5
Corrosion resistanceCorrosion resistance: 5 of 5
WeldabilityWeldability: 4 of 5
CostCost: 4 of 5

Adds molybdenum for superior chloride resistance. Marine hardware, coastal construction, pool equipment, chemical processing. The correct choice where 304 would pit.

Shop 316 stainless machine screws →

410 Stainless Steel

AISI 410 · Martensitic SS · Hardened
Tensile strengthTensile strength: 4 of 5
Corrosion resistanceCorrosion resistance: 3 of 5
WeldabilityWeldability: 2 of 5
CostCost: 3 of 5

Hardenable stainless. Stronger than 304/316 but less corrosion resistant. Self-drilling screws, concrete screws, wood screws. Not suitable for marine or chemical exposure.

Shop 410 stainless machine screws →

Silicon Bronze

C65100 / C65500 · Non-ferrous
Tensile strengthTensile strength: 2 of 5
Corrosion resistanceCorrosion resistance: 5 of 5
WeldabilityWeldability: 3 of 5
CostCost: 5 of 5

Traditional marine fastener. No galvanic corrosion with copper alloy fittings. Boatbuilding, marine joinery, historic restoration. Expensive. Use where 316 SS causes galvanic issues.

Shop silicon bronze machine screws →

Brass

C36000 · Free-machining
Tensile strengthTensile strength: 2 of 5
Corrosion resistanceCorrosion resistance: 4 of 5
WeldabilityWeldability: 1 of 5
CostCost: 4 of 5

Decorative and electrical applications. Non-magnetic, non-sparking, good conductivity. Electrical panels, plumbing, decorative hardware. Not for structural or high-load use.

Shop brass machine screws →

Nylon / Plastic

Nylon 6/6 · HDPE · PEEK
Tensile strengthTensile strength: 1 of 5
Corrosion resistanceCorrosion resistance: 5 of 5
WeldabilityWeldability: 0 of 5
CostCost: 2 of 5

Non-conductive, non-magnetic, chemically inert. Electronics, chemical processing, food service. Light loads only. PEEK for high-temp environments.

Shop nylon machine screws →

Stainless Steel Grades: 304 vs 316, 410 and More

Stainless steel fasteners are not all alike. The grade determines corrosion resistance, strength and magnetic properties. "Stainless" on a product label tells you almost nothing, so always ask for the alloy designation.

Grade Series Key Alloys Magnetic? Tensile (psi) Corrosion Resistance Best Application
Austenitic (most common): non-hardenable, generally non-magnetic
304 / 18-8 300 18% Cr, 8% Ni No (slight after cold work) 70,000–100,000 Excellent general; not chlorides Food service, outdoor, pharmaceutical
304L 300 18% Cr, 8% Ni, low C No 70,000 Same as 304 + better weld zones Welded assemblies in 304 environments
316 300 16% Cr, 10% Ni, 2% Mo No 70,000–100,000 Superior; resists chlorides & acids Marine, coastal, chemical, pool
316L 300 16% Cr, 10% Ni, 2% Mo, low C No 70,000 Same as 316 + better weld zones Welded marine or chemical assemblies
321 300 18% Cr, 9% Ni, Ti stabilized No 75,000 Good general; resists sensitization High-temperature (up to 1,500°F)
Martensitic: hardenable, magnetic
410 400 12% Cr Yes 70,000–190,000 Moderate; not for wet/chemical Self-drilling screws, concrete screws
416 400 12–14% Cr, S or Se Yes 75,000–150,000 Moderate; slightly less than 410 Machined fasteners where 410 applies
431 400 16% Cr, 2% Ni Yes 125,000–200,000 Good; better than 410 High-strength bolts in mild marine
Ferritic: non-hardenable, magnetic
430 400 17% Cr Yes 65,000 Good atmospheric; not for acids Decorative trim, appliances
Precipitation hardening
17-4 PH 600 17% Cr, 4% Ni, Cu Yes 150,000–200,000 Similar to 304 Aerospace, high-strength stainless
Galling warning: Austenitic stainless (304, 316) is prone to galling (thread seizing) when tightening stainless nuts on stainless bolts. Use an anti-seize lubricant and never torque dry. This is one of the most common stainless fastener installation errors.

Fastener Coatings & Finishes: Zinc, Galvanized, Black Oxide and More

Coating selection should match the environment and structural requirements. Some coatings add significant thickness and affect thread fit, so always specify coated fasteners when critical tolerances are involved.

Finish Process Thickness Salt Spray (hrs) Thread Impact? Temp Limit Best For
Zinc-based coatings
Zinc Plated (Clear) Electroplating 0.0002" 12–36 Minimal 250°F Indoor, light service, general hardware
Zinc Plated (Yellow) Electroplating + chromate 0.0002" 96–200 Minimal 250°F Grade 5 bolts, automotive, outdoor moderate
Hot-Dip Galvanized (HDG) Molten zinc bath 0.001"–0.004" 1,000+ Significant, use HDG nuts 392°F Structural outdoor, construction, anchors
Mechanical Galvanizing Tumbling with zinc powder 0.001"–0.002" 500–1,000 Moderate, use oversized nuts 250°F Alternative to HDG for high-strength bolts
Zinc Flake (Geomet®/Dacromet®) Dip-spin coating 0.0003"–0.0008" 500–1,000 Minimal 500°F Automotive, high-strength, no hydrogen risk
Other metallic coatings
Black Oxide Chemical conversion Negligible 3–5 (dry) / 100+ (oiled) None 300°F Appearance, mild corrosion delay, tooling
Nickel Plated Electroplating 0.0002"–0.0005" 200–500 Minimal 1,200°F Electronics, decorative, high-temp
Chrome Plated Electroplating 0.0002" 200–300 Minimal 1,200°F Decorative, automotive trim
Cadmium Plated Electroplating 0.0002" 200–400 Minimal 450°F Aerospace (restricted, toxic)
Non-metallic coatings
Phosphate + Oil Chemical + lubricant Negligible 50–200 None 300°F Lubrication, break-in, mild protection
PTFE / Teflon Coating Spray/bake 0.0005"–0.002" 200–500 Some, check fit 500°F Torque-tension control, food/chemical
Epoxy Powder Coat Electrostatic spray + bake 0.002"–0.004" 500–1,000 Significant, not for threaded shafts 300°F Structural heads, non-thread surfaces
Hydrogen embrittlement warning: Electroplating processes (zinc, cadmium, chrome) can introduce hydrogen into high-strength steel (Grade 8, Class 10.9, 12.9), causing delayed brittle fracture. Parts must be baked within 4 hours of plating. For bolts above 150,000 psi tensile, mechanical galvanizing or zinc flake coatings are preferred over electroplating.

Corrosion Resistance by Material and Environment

Ratings reflect general performance. Actual service life depends on temperature, concentration, coating integrity and galvanic coupling with adjacent materials.

ExcellentGoodMarginalAvoidAvoid = not recommended
Material / Finish Indoor Dry Outdoor / Weathering High Humidity Salt Air / Coastal Direct Marine Chemical / Acid Food / Sanitary High Temp (500°F+)
Carbon steel
Plain carbon steel Excellent Avoid Avoid Avoid Avoid Avoid Avoid Marginal
Zinc plated (clear) Excellent Marginal Marginal Avoid Avoid Avoid Avoid Avoid
Zinc plated (yellow) Excellent Good Good Marginal Avoid Avoid Avoid Avoid
Hot-dip galvanized Excellent Excellent Excellent Good Marginal Avoid Avoid Avoid
Zinc flake (Dacromet) Excellent Excellent Excellent Good Marginal Avoid Avoid Good
Black oxide (oiled) Excellent Avoid Marginal Avoid Avoid Avoid Avoid Marginal
Stainless steel
410 SS Excellent Good Good Marginal Avoid Avoid Marginal Good
304 / 18-8 SS Excellent Excellent Excellent Good Marginal Marginal Excellent Good
316 SS Excellent Excellent Excellent Excellent Good Good Excellent Good
17-4 PH SS Excellent Excellent Excellent Good Marginal Marginal Excellent Good
Non-ferrous
Silicon bronze Excellent Excellent Excellent Excellent Excellent Marginal Good Avoid
Brass Excellent Good Good Marginal Marginal Marginal Good Avoid
Nylon / plastic Excellent Good Excellent Excellent Excellent Excellent Excellent Avoid
Galvanic corrosion: When two dissimilar metals contact each other in a conductive environment (moisture), the less noble metal corrodes faster. Common problem pairs: steel bolt in aluminum structure, stainless in carbon steel, brass in steel. Use isolation washers, compatible materials, or conductive grease to mitigate.

Best Fastener Material for Every Environment

Match your application environment to the correct material and finish combination. When in doubt, upgrade rather than downgrade. The cost difference is small compared to failure or premature replacement.

Environment First Choice Second Choice Avoid Notes
Dry / indoor
Interior, climate controlled Plain or zinc-plated carbon steel Stainless (overkill) None Most economical choice; no corrosion risk
Interior, high humidity (greenhouse, laundry) Zinc yellow / HDG 304 SS Plain steel Condensation causes rust on plain steel quickly
Food processing / sanitary 316 SS (electropolished) 304 SS Any plated carbon steel Plating can contaminate; 316 preferred for washdown and chlorinated sanitizers
Outdoor / exposed
General outdoor (non-coastal) Hot-dip galvanized 304 SS or zinc flake Zinc electroplated HDG provides 20–50 year life in typical outdoor service
Pressure-treated lumber (ACQ/CA) Hot-dip galvanized (ASTM A153) or 316 SS 316 SS Zinc plated, plain, 304 SS ACQ/CA treatments are corrosive to zinc and 304 SS
Coastal / salt air (within 1 mile of ocean) 316 SS HDG with frequent inspection 304 SS, zinc plated 316 is the minimum for coastal; silicon bronze for submerged
Direct marine (submerged or splash zone) 316 SS or silicon bronze Titanium (specialty) 304 SS, any carbon steel 316 still pits in prolonged submersion; silicon bronze is traditional standard
Industrial / specialty
Chemical / acid exposure 316 SS or Hastelloy Nylon/PTFE (light loads) Carbon steel, 304 SS, brass Check specific chemical compatibility. No single answer
High temperature (300–800°F) A286 superalloy or 321 SS 316 SS to 500°F Zinc or cadmium coatings Most zinc coatings break down above about 400°F
High temperature (800–1800°F) Inconel / Hastelloy 310 SS Standard carbon or SS Specialty alloys only; standard stainless loses strength rapidly above 800°F
Cryogenic / very low temp 316L SS or A286 Inconel High-carbon steel Carbon steel becomes brittle below −40°F; austenitic SS retains toughness
Automotive / high-vibration Grade 8 / Class 10.9 with zinc flake Grade 8 yellow zinc Plain carbon steel Zinc flake preferred. No hydrogen embrittlement risk at high strength levels
Electrical / electronics Brass or stainless Nickel plated carbon Zinc plated (contact resistance) Brass for conductivity; stainless for non-magnetic; nylon for isolation
Pool / chlorinated water 316 SS Silicon bronze 304 SS, HDG, any carbon steel Chlorine attacks 304 SS; 316 is minimum standard for pool hardware

Frequently Asked Questions

What is the difference between 304 and 316 stainless steel fasteners?

316 adds about 2% molybdenum, which gives it superior resistance to chlorides and acids. Use 316 for marine, coastal, pool and chemical applications. 304 (18-8) is the most common stainless grade and works well for food service, outdoor hardware and light marine use, but it can pit in chloride-heavy environments.

Is hot-dip galvanized better than zinc plated?

For outdoor use, yes. Hot-dip galvanizing is 0.001" to 0.004" thick and rated 1,000+ hours in salt spray, compared with 12 to 36 hours for clear zinc plating. The thicker coating affects thread fit, so pair HDG bolts with HDG nuts. Zinc plating is the economical choice for indoor and light service.

What fasteners should I use with pressure-treated lumber?

Use hot-dip galvanized (ASTM A153) or 316 stainless. ACQ and CA lumber treatments are corrosive to zinc plated, plain steel and 304 stainless fasteners.

Are stainless steel fasteners magnetic?

300 series austenitic grades such as 304 and 316 are generally non-magnetic, though 304 can become slightly magnetic after cold work. 400 series grades (410, 416, 431, 430) and 17-4 PH are magnetic.

How do I prevent galling on stainless steel bolts?

Austenitic stainless (304, 316) is prone to galling, or thread seizing, when stainless nuts are tightened on stainless bolts. Use an anti-seize lubricant and never torque dry.

What is hydrogen embrittlement?

Electroplating (zinc, cadmium, chrome) can introduce hydrogen into high-strength steel such as Grade 8, Class 10.9 and 12.9, causing delayed brittle fracture. Parts must be baked within 4 hours of plating. For bolts above 150,000 psi tensile, mechanical galvanizing or zinc flake coatings are preferred.

What is galvanic corrosion and how do I prevent it?

When two dissimilar metals touch in the presence of moisture, the less noble metal corrodes faster. Common problem pairs are a steel bolt in aluminum, stainless in carbon steel, and brass in steel. Use isolation washers, compatible materials or conductive grease.

Need help choosing a material?

We stock fasteners in plain, zinc, hot-dip galvanized, 18-8 stainless, 316 stainless, and specialty materials, from standard hardware to military and aerospace specifications. Serving customers since 1947.

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Material properties per ASTM, SAE, and ISO standards. Corrosion ratings are general guidance. Actual performance varies with temperature, concentration, surface condition, and application. Consult material certifications and an engineer for critical applications.