Stainless Steel Fastener Grades: 18-8 vs 304 vs 316 vs 410

Choosing the right stainless steel grade is simple when you know the basics. This guide explains 18-8, 304, 316, and 410 stainless steel fasteners in plain language.

Quick Comparison Chart

18-8 Stainless Steel
Best For: Indoor use, general hardware
Strength: 75,000 PSI
Corrosion Resistance: Good
Cost: Lowest stainless option

304 Stainless Steel
Best For: Food service, indoor/outdoor
Strength: 75,000 PSI
Corrosion Resistance: Excellent
Cost: Moderate

316 Stainless Steel
Best For: Marine, coastal, salt water
Strength: 75,000 PSI
Corrosion Resistance: Superior
Cost: 40-70% more than 304

410 Stainless Steel
Best For: High strength applications
Strength: 110,000-150,000 PSI
Corrosion Resistance: Good
Cost: Moderate

18-8 Stainless Steel

18-8 contains 18% chromium and 8% nickel. This is the most affordable stainless steel option for basic corrosion resistance.

When to Use 18-8

✓ Indoor applications
✓ Restaurant equipment
✓ General hardware
✓ Dry environments
✓ Budget projects

When NOT to Use 18-8

✗ Salt water exposure
✗ Coastal areas
✗ Road salt environments
✗ When certifications required

304 Stainless Steel

304 is the most common stainless steel grade. It performs similar to 18-8 but meets strict standards and comes with certifications.

What Makes 304 Different

304 follows ASTM standards with documented quality. This makes it required for food service, medical, and pharmaceutical applications.

Common Uses for 304

✓ Food processing equipment
✓ Commercial kitchens
✓ Pharmaceutical equipment
✓ Brewing equipment
✓ Medical devices
✓ Architectural hardware (inland)

304 vs 18-8: What’s the Difference?

They perform almost the same. Use 304 when you need certifications or work in regulated industries. Use 18-8 to save money on general hardware.

316 Stainless Steel (Marine Grade)

316 is called “marine grade” because it resists salt water. It contains 2-3% molybdenum that prevents pitting from chlorides.

When to Use 316

✓ Boats and docks
✓ Coastal buildings (within 10 miles of ocean)
✓ Direct salt water contact
✓ Swimming pools
✓ Road salt exposure
✓ Chemical plants
✓ Bridge construction

Is 316 Worth the Extra Cost?

Yes, if you’re near salt water. 316 costs 40-70% more than 304, but prevents corrosion failures. Within 10 miles of the ocean or anywhere road salt is used, always choose 316.

316 vs 304: When to Upgrade

Choose 316 if:
– Near salt water
– Coastal location
– Road salt exposure
– Replacement would be expensive

Choose 304 if:
– Inland location
– No salt exposure
– Indoor application
– Budget is limited

410 Stainless Steel

410 is different from other grades. It can be hardened for much higher strength but has less corrosion resistance.

Key Features of 410

• Much stronger than 304/316
• Magnetic (304 and 316 are not)
• Can be heat treated
• Lower corrosion resistance
• No nickel content

When to Use 410

✓ High-strength applications
✓ Pump components
✓ Valve trim
✓ Turbine fasteners
✓ Mild corrosive environments

When NOT to Use 410

✗ Marine environments
✗ Food processing
✗ Pharmaceutical use
✗ Maximum corrosion resistance needed

Strength Comparison

Important: Stainless steel is weaker than carbon steel.

Tensile strength for 1/2″ bolt:
Grade 5 Carbon Steel: 11,000 lbs
Grade 8 Carbon Steel: 14,000 lbs
18-8/304/316 Stainless: 7,000 lbs
410 Stainless: 10,500 lbs

What this means: Stainless steel (304/316) is about 35-40% weaker than Grade 5 carbon steel. When replacing carbon steel with stainless, you may need larger bolts or more fasteners.

How to Choose the Right Grade

By Environment

Indoor: Use 18-8 or 304
Outdoor (inland): Use 304
Outdoor (coastal): Use 316
Marine/salt water: Use 316
Road salt areas: Use 316

By Industry

Food Service: Use 304
Pharmaceutical: Use 304 or 316L
Marine: Use 316 only
Construction (inland): Use 304
Construction (coastal): Use 316

Common Mistakes to Avoid

Mistake 1: Using 304 in Salt Water

304 will corrode in marine environments. Always use 316 for boats, docks, and coastal construction.

Mistake 2: Direct Substitution

Don’t replace a Grade 5 bolt with the same size in stainless. Stainless is weaker. Use larger sizes or consult an engineer.

Mistake 3: No Anti-Seize

Stainless steel can gall (cold weld) during installation. Always use anti-seize compound on threads.

Mistake 4: Stainless with Aluminum

Stainless fasteners corrode aluminum through galvanic corrosion. Use isolating washers or aluminum fasteners.

Mistake 5: Assuming Rust-Proof

All stainless steel can corrode. “Stainless” means stain-resistant, not rust-proof. Choose the right grade for your environment.

Frequently Asked Questions

Is 316 stronger than 304?

No. Both have the same strength (75,000 PSI). 316 has better corrosion resistance, not more strength.

Can I use 304 on a boat?

No. Always use 316 for marine applications. 304 will pit and corrode in salt water.

Why is 316 more expensive?

The molybdenum content (2-3%) makes it costlier but dramatically improves salt water resistance.

Are stainless bolts magnetic?

304 and 316 are non-magnetic. 410 is magnetic.

What does “L” mean in 304L?

“L” means low-carbon. Low-carbon grades resist corrosion better after welding or high-temperature exposure.

Can stainless steel rust?

Yes, under certain conditions. All stainless can corrode in aggressive environments. Choose the appropriate grade.

Cost Comparison

Relative costs compared to carbon steel:

Carbon Steel (zinc plated): 1x (baseline)
18-8 Stainless: 3-4x
304 Stainless: 3-5x
316 Stainless: 5-7x
410 Stainless: 2.5-4x

Simple Selection Guide

Use 304 For:

✓ Most general applications
✓ Food service
✓ Indoor and outdoor (inland)
✓ When certifications needed

Use 316 For:

✓ Marine and coastal
✓ Salt water contact
✓ Swimming pools
✓ Road salt areas

Use 410 For:

✓ High strength needs
✓ Mild corrosion environment
✓ Pump/valve components

Conclusion

Choosing stainless steel grades is straightforward:

For most projects: Use 304 stainless steel. It offers excellent corrosion resistance at a reasonable price.

Near salt water: Use 316 stainless steel. The extra cost prevents expensive corrosion failures.

Need high strength: Use 410 if the environment is mild, or use larger 304/316 fasteners.

Remember: Stainless steel is weaker than carbon steel. Don’t directly substitute without checking load requirements.

When in doubt, contact your fastener distributor. They can help select the right grade for your specific application.