For snap-in pcb standoffs 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 Snap-In PCB Standoffs
Specified for marine, coastal and chemical applications. For snap-in pcb standoffs, 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 Snap-In PCB Standoffs in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
For stainless snap-in pcb standoffs the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Snap-In PCB Standoffs Available in A4 Stainless Steel
| Spacing height (mm) | Body diameter (mm) | Fits board hole (mm) | Fits chassis hole (mm) | Board thickness (mm) | Material | Flammability | Colour |
|---|---|---|---|---|---|---|---|
| 4.8 | 6.0 | 4.0 | 4.0 | 1.6 | Nylon 6/6 | UL94 V-2 | Natural |
| 6.4 | 6.0 | 4.0 | 4.0 | 1.6 | Nylon 6/6 | UL94 V-2 | Natural |
| 9.5 | 6.0 | 4.0 | 4.0 | 1.6 | Nylon 6/6 | UL94 V-2 | Natural |
| 12.7 | 6.0 | 4.0 | 4.0 | 1.6 | Nylon 6/6 | UL94 V-0 | Black |
| 15.9 | 6.0 | 4.0 | 4.0 | 1.6 | Nylon 6/6 | UL94 V-0 | Black |
| 19.1 | 6.0 | 4.0 | 4.0 | 2.0 | Nylon 6/6 | UL94 V-0 | Black |
