Material Grades – Stainless Steel Fasteners
Stainless steel fasteners are widely used for their strength, durability, and excellent resistance to corrosion. They are manufactured in different material grades to suit various environmental and mechanical requirements.
Understanding these grades helps you select the right fastener for your application, ensuring safety, reliability, and long-term performance.
Common Grades of Stainless Steel Fasteners
1. AISI 304 / Grade A2
- Description: The most commonly used stainless steel grade.
- Corrosion Resistance: Good resistance to rust and corrosion in general environments.
- Applications: Indoor use, automotive, food processing, architectural work.
- Equivalent Standard: ASTM F593 Group 1
- Non-magnetic in annealed condition.
2. AISI 316 / Grade A4
- Description: Known as marine-grade stainless steel.
- Corrosion Resistance: Superior resistance to saltwater, chemicals, and harsh environments due to added molybdenum (Mo).
- Applications: Marine hardware, chemical plants, medical equipment, coastal construction.
- Equivalent Standard: ASTM F593 Group 2
- Non-magnetic, highly corrosion-resistant.
ASTM Grades for Stainless Steel Fasteners
- ASTM A193 Grade B8Equivalent to AISI 304. Commonly used for bolts, studs, and threaded rods in high-temperature or pressure applications.
- ASTM A193 Grade B8MEquivalent to AISI 316. Preferred for use in corrosive environments like offshore platforms and chemical industries.
- ASTM A194 Grade 8 / 8MThese grades apply to stainless steel nuts matching A193 B8 and B8M bolts.
Comparison Table
| Grade | AISI | ASTM Equivalent | Corrosion Resistance | Strength | Magnetic |
|---|---|---|---|---|---|
| A2 | 304 | B8 | Good | Medium | No |
| A4 | 316 | B8M | Excellent | Medium | No |
How to Choose the Right Grade
- Use AISI 304 (A2/B8) for general purpose, non-aggressive environments.
- Use AISI 316 (A4/B8M) for marine, coastal, or chemical exposure.