For hex standoffs, male-female in A4 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) is summarized below together with every size supplied.
Why Choose A4 Stainless Steel for Hex Standoffs, Male-Female
Specified for marine, coastal and chemical applications. For hex standoffs, male-female, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Hex Standoffs, Male-Female in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless hex standoffs, male-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
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Hex Standoffs, Male-Female Available in A4 Stainless Steel
| Thread size | Across flats s (mm) | Body length L (mm) | Male stud length (mm) | Material | Finish | Length convention |
|---|---|---|---|---|---|---|
| M3 | 5.5 | 10 | 6 | Brass | Nickel plated | Body only, stud extra |
| M3 | 5.5 | 20 | 6 | Brass | Nickel plated | Body only, stud extra |
| M3 | 5.5 | 30 | 6 | Brass | Nickel plated | Body only, stud extra |
| M4 | 7.0 | 15 | 8 | Brass | Nickel plated | Body only, stud extra |
| M4 | 7.0 | 25 | 8 | Stainless (A2) | Passivated | Body only, stud extra |
| M5 | 8.0 | 25 | 10 | Stainless (A2) | Passivated | Body only, stud extra |
