A4 acid-resistant hex screws in accordance with DIN 931/933 (ISO 4014/4017). Made of A4 acid-resistant stainless steel (AISI 316) to ISO 3506-1, they offer excellent corrosion resistance and are suitable for both indoor and outdoor use, including maritime and corrosive environments. The screws come in two variants, partially threaded and fully threaded. They are ideal for a range of construction and assembly projects where durability and corrosion resistance are essential, particularly in offshore fastener applications with chloride exposure where A2 is not sufficient. Specification Standard: DIN 931 / ISO 4014 (partially threaded) and DIN 933 / ISO 4017 (fully threaded) Material: A4 acid-resistant stainless steel, AISI 316, molybdenum content 2 to 3 percent Material standard: ISO 3506-1 Strength level: Class 70 (700 MPa) and class 80 (800 MPa) Corrosion resistance: Seawater, chlorides, chemical process environments Available finish: Partially threaded (DIN 931) and fully threaded (DIN 933) Key properties A4 acid-resistant hex screw DIN 931/933 in AISI 316 is the mandatory specification for offshore, marine and chloride-exposed installation. A2 does not give sufficient protection in these environments. ISO 3506-1 class 70 and 80 have lower strength than carbon steel 8.8/10.9. Preload and dimensions are calculated separately. For subsea and highly aggressive environments where A4 is not sufficient, Super Duplex to ASTM A182 F55 is a good alternative.