Material specification page for double-end studs (din 938 / 939 / 940) in A2 Stainless Steel. Covers the grade designation (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to DIN 938.
Why Choose A2 Stainless Steel for Double-End Studs (DIN 938 / 939 / 940)
The most common stainless group for indoor and general outdoor fasteners. For double-end studs (din 938 / 939 / 940), 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 Double-End Studs (DIN 938 / 939 / 940) 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 Double-End Studs (DIN 938 / 939 / 940), the alternative stainless grade is A4 (316). Choose A2 (304) for general use and A4 (316) wherever chlorides are present; the molybdenum in A4 is the whole difference. Remember that stainless is the corrosion answer, not the strength answer — for load, look at class 8.8 or 10.9 instead.
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 Double-End Studs (DIN 938 / 939 / 940) Available in A2 Stainless Steel
| Thread size | Metal end bm (mm) | For parent material | Nut end (mm) | Common overall length (mm) | Property class | Reference standard | Sibling standard |
|---|---|---|---|---|---|---|---|
| M8 | 8 | Steel | 8 | 30~80 | 8.8 | DIN 938 | DIN 939 = 10 mm, DIN 940 = 16 mm |
| M10 | 10 | Steel | 10 | 35~100 | 8.8 | DIN 938 | DIN 939 = 12.5 mm, DIN 940 = 20 mm |
| M12 | 12 | Steel | 12 | 40~120 | 8.8 | DIN 938 | DIN 939 = 15 mm, DIN 940 = 24 mm |
| M16 | 16 | Steel | 16 | 50~160 | 8.8 | DIN 938 | DIN 939 = 20 mm, DIN 940 = 32 mm |
| M20 | 20 | Steel | 20 | 60~200 | 8.8 | DIN 938 | DIN 939 = 25 mm, DIN 940 = 40 mm |
| M24 | 24 | Steel | 24 | 70~240 | 8.8 | DIN 938 | DIN 939 = 30 mm, DIN 940 = 48 mm |
