Technically reviewed by Vincent, Founder at HEXVARO
Last reviewed
A2 vs A4 comparison
| Factor | A2 | A4 |
|---|---|---|
| Similar steel grade | 304 (1.4301) | 316 (1.4401) |
| Molybdenum | No | Yes |
| Corrosion resistance | Good for general outdoor use | Better in chloride environments |
| Typical use | Building, food equipment, general outdoor work | Coastal, marine, chemical and pool areas |
| Price | Lower | Higher |
What A2-70 and A4-80 mean
A designation such as A4-80 has a steel group and corrosion number (A4), then a property class (80). Class 70 means a minimum tensile strength of 700 MPa and class 80 means 800 MPa. Classes come from ISO 3506.
Common questions on site
- Magnetism: A2 and A4 are largely non-magnetic, but cold working can add some magnetism.
- Galling: stainless threads can seize under load, so consider slower tightening or a suitable lubricant.
- Mixed metals: keep stainless fasteners away from conditions that cause bimetallic corrosion, and match them to the parent material.
- Strength: A4-80 has a similar tensile strength to 8.8 carbon steel, but always check the design values.
How to specify stainless fasteners
- Product standard and size.
- Grade and class, for example A2-70 or A4-80.
- Service environment, such as coastal or chemical.
- Certificates required, for example EN 10204 3.1.
- Quantity per size, packing and destination.
Frequently asked questions
Is A4 stronger than A2?
Not by grade alone. Strength comes from the property class, so A2-70 and A4-70 have the same minimum tensile strength.
Is A2 the same as 304?
A2 is similar to 304 stainless. A2 is the fastener grade name, and 304 is a steel grade.
When should I use A4 instead of A2?
Use A4 on coastal sites, in marine and chemical plants, and in other chloride-rich environments.
Are stainless steel bolts magnetic?
A2 and A4 are largely non-magnetic, but cold working can make them slightly magnetic.
Products to this standard
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