A4 Stainless Steel Metric Cap Nuts
What are A4 stainless steel cap nuts? A4 stainless steel metric cap nuts are closed-top domed nuts in metric threads that cover exposed bolt ends for a finished, safe look. Made from A4 stainless, a molybdenum-alloyed marine grade comparable to 316, they resist salt and chloride corrosion in coastal, marine, and outdoor use.
Why A4 is the marine choice for metric cap nuts
A4 is the metric designation for a marine-grade austenitic stainless, containing added molybdenum that gives it far better resistance to salt and chloride pitting than A2 (comparable to 304). That makes A4 cap nuts the right pick for boats, docks, coastal railings, and anywhere metric hardware faces saltwater or spray. The domed top hides the bolt threads for a clean, snag-free finish while the A4 grade keeps that finish rust-free where A2 would stain.
A4 vs A2 metric cap nuts
- A4: molybdenum-alloyed marine grade, comparable to 316, for salt and chloride exposure.
- A2: comparable to 304, strong general corrosion resistance for indoor and inland outdoor use.
- Both: austenitic, largely non-magnetic, and bright-finished for visible hardware.
Common applications for A4 cap nuts
- Boats, docks, and marine hardware
- Coastal railings and outdoor fixtures
- Metric assemblies exposed to salt or chlorides
- Visible bolt ends needing a finished, snag-free look
Pair these with A4 metric bolts and nuts, and browse standard, high crown, and every metric size on the main cap nuts category.
A4 Stainless Steel Metric Cap Nuts FAQ
Is A4 stainless the same as 316?
A4 is the metric grade comparable to 316. Both are molybdenum-alloyed austenitic stainless with excellent resistance to salt and chlorides.
When should I choose A4 over A2?
Choose A4 for coastal, saltwater, and chloride exposure. A2, comparable to 304, is fine for indoor and general outdoor use.
What is the difference between a cap nut and an acorn nut?
They are the same. Both describe a closed-top nut with a domed end that covers the bolt threads.