For push-on nuts (starlock retainers) 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 Push-On Nuts (Starlock Retainers)
Specified for marine, coastal and chemical applications. For push-on nuts (starlock retainers), 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 Push-On Nuts (Starlock Retainers) in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
For stainless push-on nuts (starlock retainers) 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
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 Push-On Nuts (Starlock Retainers) Available in A4 Stainless Steel
| For shaft diameter (mm) | Outer diameter (mm) | Thickness (mm) | Teeth | Push-off resistance (N, typical) | Material | Finish | Reusable |
|---|---|---|---|---|---|---|---|
| 3.0 | 11.0 | 0.25 | 12 | 150 | Spring steel | Bright zinc | No |
| 4.0 | 12.0 | 0.25 | 12 | 220 | Spring steel | Bright zinc | No |
| 5.0 | 15.0 | 0.30 | 12 | 320 | Spring steel | Bright zinc | No |
| 6.0 | 18.0 | 0.30 | 12 | 420 | Spring steel | Bright zinc | No |
| 8.0 | 21.0 | 0.40 | 12 | 600 | Spring steel | Bright zinc | No |
| 10.0 | 26.0 | 0.40 | 12 | 780 | Spring steel | Bright zinc | No |
