A4 stainless steel screws are fasteners made from A4 stainless steel, which is also known as Type 316 stainless steel. This material is an austenitic stainless steel alloy that includes chromium, nickel, molybdenum, carbon, silicon, manganese, phosphorus, and sulfur. The addition of molybdenum (2-3%) distinguishes A4 from the more common A2 (304) stainless steel and provides enhanced resistance to corrosion, especially pitting and crevice corrosion, making A4 screws highly resistant to saltwater, salt spray, and harsh chemical environments. This quality makes them known as "marine grade" stainless steel fasteners.
Compared to A2 stainless steel screws, A4 screws have superior durability in marine, chemical, and extreme temperature environments, and they are less reactive with other materials. They are often used in applications requiring high corrosion resistance, such as marine engineering, chemical processing, medical instruments, and outdoor installations subject to corrosive elements. A4 stainless steel screws are typically more expensive than A2, but their enhanced resistance often results in lower maintenance and longer service life in harsh environments.
A4 stainless steel screws come in various strength grades such as A4-70 and A4-80, denoting their tensile strength (700 MPa and 800 MPa respectively). These screws can be easier to fabricate, clean, finish, and weld compared to A2 due to their chemical composition.
In summary, A4 stainless steel screws are corrosion-resistant, durable fasteners made from Type 316 stainless steel, ideal for marine, chemical, and high-corrosion environments where long-term performance and resistance to rust and pitting are critical
