A4 fasteners are made from marine-grade stainless steel (typically AISI 316). They’re chosen when strength must be combined with excellent corrosion resistance.

Key Benefits

1. Superior corrosion resistance

   • Excellent performance in saltwater, coastal, and marine environments

   • Highly resistant to chlorides, acids, and industrial chemicals

2. Ideal for harsh conditions

   • Suitable for outdoor, chemical, and high-humidity applications

   • Performs well where A2 (304) fasteners may corrode

3. Good mechanical strength

   • Common strength class: A4-70 (≈700 MPa tensile strength)

   • Reliable for structural and load-bearing assemblies

4. High temperature resistance

   • Maintains properties at elevated temperatures better than carbon steel

5. Low maintenance & long service life

   • No need for protective coatings or frequent replacement

   • Reduces lifecycle cost despite higher initial price

6. Non-magnetic (generally)

   • Useful in electrical, electronic, and sensitive equipment installations

7. Clean & aesthetic finish

   • Preferred in food processing, pharmaceutical, and architectural uses

Typical Applications

• Marine & offshore equipment

• Chemical plants and refineries

• Coastal buildings and infrastructure

• Food & dairy processing machinery

• Medical and pharmaceutical equipment

A4-80

 

Acceptable PPM Levels

If a customer assembles 20 000 screws per day
and the batch has a PPM value of 500 it means that there
is 10 defect parts in the batch. This causes 10 stops in
the automatic assemblage. If each stop takes 5 minutes
to correct it will take 50 minutes each day to rectify. The
cost will be enormous.

Marking on SS screws.

Hexagon and Hex Socket Screws from nominal diameter M5 must be marked.The marking must show the steel group, the property class and the manufacturer's mark.

SS-A2

Stainless Steel of Type A2 is most frequently used. They are, however, unsuitable for use in non-oxidizing acids and media containing chlorides (like swimming pools, salt water etc.)