Premier Stainless Steel Fasteners: Corrosion-Proof from Coil to Carton

A2 grade corresponds to SS 304 (18% chromium, 8% nickel) — good for general and indoor use. A4 grade is SS 316 (16% chromium, 10% nickel, 2% molybdenum) — molybdenum dramatically improves pitting resistance in chloride-containing environments like seawater. A4 costs 25–40% more but lasts decades longer in marine service.

The number is the minimum tensile strength in 10 MPa units. A2-70 stainless reaches 700 MPa minimum tensile strength. A4-80 reaches 800 MPa. The cold-working that produces these strengths makes the steel slightly magnetic — this is normal for cold-worked austenitic stainless.

Austenitic stainless (304, 316) is non-magnetic in fully annealed condition. Cold working — which happens during fastener forming — disrupts the austenite structure and introduces slight ferromagnetism. This is normal and does not indicate the wrong grade or quality issue.

The L stands for low carbon (max 0.03% C vs 0.08% in standard 316). Use 316L whenever the fastener will be welded — the low carbon prevents chromium carbide precipitation at grain boundaries during welding, which would otherwise cause inter-granular corrosion in service.

Yes. All finished stainless fasteners go through nitric acid or citric acid passivation per ASTM A967. The process removes free iron from the surface and restores the chromium oxide passive layer that gives stainless its corrosion resistance.

Yes — austenitic stainless (304 and 316) is prone to thread galling when stainless mates with stainless under load. We recommend using anti-seize lubricant on threads, installing at slower torque rates, and pairing different grades when possible (e.g., 316 bolt with 304 nut).