A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is the most common stainless group for indoor and general outdoor fasteners. Specified on insulating fibre washers it determines the corrosion behaviour (good general corrosion resistance) and the service temperature range (approx. -200 °C to +400 °C, subject to the property class and the joint); the dimensions are ours rather than a standard's, and are listed in full below.
Why Choose A2 Stainless Steel for Insulating Fibre Washers
The most common stainless group for indoor and general outdoor fasteners. For insulating fibre washers, this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Good general corrosion resistance |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for Insulating Fibre Washers in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Galvanic & Galling Considerations
For stainless insulating fibre washers the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.
Using Stainless Fasteners in Aluminum
The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.
Sizes of Insulating Fibre Washers Available in A2 Stainless Steel
| For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Dielectric strength (kV/mm) | Max temperature (°C) | Moisture |
|---|---|---|---|---|---|---|
| M3 | 3.2 | 7.0 | 0.5 | 10 | 105 | Hygroscopic — indoor use |
| M4 | 4.3 | 9.0 | 0.5 | 10 | 105 | Hygroscopic — indoor use |
| M5 | 5.3 | 10.0 | 0.8 | 10 | 105 | Hygroscopic — indoor use |
| M6 | 6.4 | 12.0 | 0.8 | 10 | 105 | Hygroscopic — indoor use |
| M8 | 8.4 | 16.0 | 1.0 | 10 | 105 | Hygroscopic — indoor use |
| M10 | 10.5 | 20.0 | 1.0 | 10 | 105 | Hygroscopic — indoor use |
Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in A2 Stainless Steel. The catalogue's default material column has been omitted here so it cannot be read as contradicting that.
Custom manufacturing · Made to drawing
Need this washer in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Bore, outside diameter, thickness, temper and finish are the variables here — there is no thread to specify, so the fit and the bearing area are what the drawing has to pin down. Made by stamping or punching.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
