For round standoffs, female-female in A2 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70) is summarized below together with every size supplied.
Why Choose A2 Stainless Steel for Round Standoffs, Female-Female
The most common stainless group for indoor and general outdoor fasteners. For round standoffs, female-female, 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 Round Standoffs, Female-Female 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
Two important notes for stainless round standoffs, female-female: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.
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 Round Standoffs, Female-Female Available in A2 Stainless Steel
| Thread size | Outer diameter (mm) | Length L (mm) | Thread depth each end (mm) | Material | Finish | Note |
|---|---|---|---|---|---|---|
| M3 | 5.0 | 10 | 6 | Brass | Nickel plated | Female both ends |
| M3 | 5.0 | 15 | 6 | Brass | Nickel plated | Female both ends |
| M3 | 5.0 | 25 | 6 | Brass | Nickel plated | Female both ends |
| M4 | 6.0 | 15 | 8 | Brass | Nickel plated | Female both ends |
| M4 | 6.0 | 30 | 8 | Stainless (A2) | Passivated | Female both ends |
| M5 | 8.0 | 20 | 10 | Stainless (A2) | Passivated | Female both ends |
| M5 | 8.0 | 40 | 10 | Stainless (A2) | Passivated | Female both ends |
