Material specification page for automotive push-type retainers in A4 Stainless Steel. Covers the grade designation (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to Trade series (automotive push-type retainers).
Why Choose A4 Stainless Steel for Automotive Push-Type Retainers
Specified for marine, coastal and chemical applications. For automotive push-type 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 Automotive Push-Type Retainers in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Automotive Push-Type Retainers, the alternative stainless grade is A2 (304). A2 (304) covers general indoor and outdoor service. A4 (316) adds molybdenum, which is what buys the chloride resistance for marine and de-icing-salt exposure. Where strength matters more than corrosion, plated alloy steel in class 8.8 or 10.9 is the swap to make.
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 Automotive Push-Type Retainers Available in A4 Stainless Steel
| Installation | Rear access | Fit governed by | Reusable |
|---|---|---|---|
| pushed in by hand | not required | panel hole, panel thickness, head diameter | usually not |
| pushed in, screw-expanded centre | not required | panel hole, panel thickness, head diameter | yes, with care |
| pushed in, fir-tree stem | not required | panel hole and panel thickness | usually not |
