Specifying Flat Washers in A2 Stainless Steel pairs the dimensional form of Flat Washers (ISO 7089 / ISO 7093) with the engineering properties of A2 Stainless Steel. This page explains when to choose the grade, how it behaves in service, and which grades to compare it against.
Why Choose A2 Stainless Steel for Flat Washers
The most common stainless grade for indoor and general outdoor fasteners. For flat washers, this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | A2-70 (304) |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C |
| 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 Flat Washers in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Comparable Grades
For Flat Washers, the alternative stainless grade is A4 (316). A2 (304) suits general indoor and outdoor service; A4 (316) adds molybdenum for marine and chloride environments. Where higher strength matters more than corrosion, switch to plated alloy-steel class 8.8 or 10.9.
Sizes of Flat Washers Available in A2 Stainless Steel
| For bolt size | Inner diameter d1 min (mm) | Outer diameter d2 max (mm) | Thickness h (mm) | Reference standard |
|---|---|---|---|---|
| M1.6 | 1.7 | 4.0 | 0.3 | ISO 7089 |
| M2 | 2.2 | 5.0 | 0.3 | ISO 7089 |
| M2.5 | 2.7 | 6.0 | 0.5 | ISO 7089 |
| M3 | 3.2 | 7.0 | 0.5 | ISO 7089 |
| M3.5 | 3.7 | 8.0 | 0.5 | ISO 7089 |
| M4 | 4.3 | 9.0 | 0.8 | ISO 7089 |
| M5 | 5.3 | 10.0 | 1.0 | ISO 7089 |
| M6 | 6.4 | 12.0 | 1.6 | ISO 7089 |
| M7 | 7.4 | 14.0 | 1.6 | ISO 7089 |
| M8 | 8.4 | 16.0 | 1.6 | ISO 7089 |
| M10 | 10.5 | 20.0 | 2.0 | ISO 7089 |
| M12 | 13.0 | 24.0 | 2.5 | ISO 7089 |
| M14 | 15.0 | 28.0 | 2.5 | ISO 7089 |
| M16 | 17.0 | 30.0 | 3.0 | ISO 7089 |
| M18 | 19.0 | 34.0 | 3.0 | ISO 7089 |
| M20 | 21.0 | 37.0 | 3.0 | ISO 7089 |
| M22 | 23.0 | 39.0 | 3.0 | ISO 7089 |
| M24 | 25.0 | 44.0 | 4.0 | ISO 7089 |
| M27 | 28.0 | 50.0 | 4.0 | ISO 7089 |
| M30 | 31.0 | 56.0 | 4.0 | ISO 7089 |
| M33 | 34.0 | 60.0 | 5.0 | ISO 7089 |
| M36 | 37.0 | 66.0 | 5.0 | ISO 7089 |
| M39 | 40.0 | 72.0 | 6.0 | ISO 7089 |
| M42 | 43.0 | 78.0 | 7.0 | ISO 7089 |
| M45 | 46.0 | 85.0 | 7.0 | ISO 7089 |
| M48 | 50.0 | 92.0 | 8.0 | ISO 7089 |
| M52 | 54.0 | 98.0 | 8.0 | ISO 7089 |
| M56 | 58.0 | 105.0 | 9.0 | ISO 7089 |
| M60 | 62.0 | 110.0 | 9.0 | ISO 7089 |
| M64 | 66.0 | 115.0 | 9.0 | ISO 7089 |