A4 (316) STAINLESS

A4 stainless steel hexagon full nuts, also known as 316 grade or marine grade, are the premium choice for fasteners in highly corrosive environments.

he key difference from the standard A2 (304) grade is the addition of 2–3% molybdenum, which provides superior resistance to pitting and crevice corrosion. 

Core Technical Properties

  • Corrosion Resistance: Engineered specifically to withstand chlorides, salt spray, and industrial acids. They are essential for applications submerged in saltwater or exposed to coastal air.
  • Strength Classes:
    • A4-50: Soft, often for turned or soft-pressed fasteners.
    • A4-70: The most common grade, cold-worked with a minimum tensile strength of 700 MPA
    • A4-80: High-tensile stainless, providing a minimum tensile strength of 800 MPA for critical load-bearing applications.
  • Standards: Typically manufactured to DIN 934 or the newer ISO 4032. A4 nuts should ideally be paired with A4 bolts to ensure uniform corrosion resistance across the entire assembly. 

Critical Use Cases

  • Marine & Offshore: Boat fittings, rigging hardware (shackles, turnbuckles), and subsea oil and gas installations.
  • Chemical & Food Processing: Equipment exposed to aggressive cleaning agents, acids, and halogenated media.
  • Infrastructure: Coastal bridges, water treatment plants, and solar PV racking systems in salt-heavy environments. 

Maintenance Tip: Prevent Galling

Like all stainless fasteners, A4 nuts are highly susceptible to galling (cold-welding). When assembling A4 nuts with A4 bolts, always use a specialized anti-seize lubricant and avoid over-torquing to prevent the threads from seizing permanently.

A4 (316) STAINLESS
METRIC THREAD

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