A4 Stainless Steel Fully-Threaded Standoff Caps combine the dimensional form of Trade series (fully threaded standoff caps) with the material properties of grade ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80: superior, including marine and chloride environments, largely non-magnetic, service range approx. -200 °C to +400 °C, subject to the property class and the joint. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose A4 Stainless Steel for Fully-Threaded Standoff Caps
Specified for marine, coastal and chemical applications. For fully-threaded standoff caps, 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 |
Galvanic & Galling Considerations
Two important notes for stainless fully-threaded standoff caps: (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.
Comparable Grades
For Fully-Threaded Standoff Caps, the alternative stainless grade is A2 (304). 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 Fully-Threaded Standoff Caps Available in A4 Stainless Steel
| Thread size | Outside diameter (in) | Cap height (in) | Thread length (in) | Material | Form |
|---|---|---|---|---|---|
| 4-40 | 1/4 | 1/4 | 3/8 | zinc-plated brass | fully threaded cap |
| 6-32 | 1/4 | 1/4 | 3/8 | zinc-plated brass | fully threaded cap |
| 8-32 | 1/4 | 1/4 | 3/8 | zinc-plated brass | fully threaded cap |
| 10-32 | 1/4 | 1/4 | 3/8 | zinc-plated brass | fully threaded cap |
