A4 stainless steel is a grade of stainless steel that contains at least 16% chromium, 10% nickel, and 2% molybdenum. It is also known as 316 stainless steel. A4 stainless steel has even better corrosion resistance than A2 stainless steel, especially in environments with high chloride levels. It is often used in marine applications, as well as in the chemical and pharmaceutical industries. Some common uses for A4 stainless steel include fasteners, surgical instruments, and architectural elements.