Material specification page for low-profile captive pins 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 (captive tack pins).
Why Choose A4 Stainless Steel for Low-Profile Captive Pins
Specified for marine, coastal and chemical applications. For low-profile captive pins, 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 Low-Profile Captive Pins in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Comparable Grades
For Low-Profile Captive Pins, the alternative stainless grade is A2 (304). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.
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 Low-Profile Captive Pins Available in A4 Stainless Steel
| Part form | Pin diameter (in) | Pin length (in) | Head diameter (in) | Head height (in) | Panel thickness (in) | Installation hole (in) | Material |
|---|---|---|---|---|---|---|---|
| T4-10-025 | 0.051 | 0.040 | 0.079 | 0.008 | 0.008~0.011; minimum 0.035 | 0.051 | 400-series stainless steel |
| TA-10-025 | 0.051 | 0.040 | 0.079 | 0.008 | 0.008~0.011; minimum 0.035 | 0.051 | aluminum |
