A4 (316) Marine Grade Stainless Steel, Screws, Nuts and Washers

A4 Stainless steel has a higher chemical composition of molybdenum which leads to greatly increased corrosion resistance making it a great choice for marine applications. A4 is Stronger than standard A2 stainless with A4 generally being as strong as medium to low carbon steel. A4 is also commonly called 316 or marine grade stainless. 

link to full article on A2 vs A4

Other common applications of 316 stainless steel include:

• Chemical processing and storage equipment.
• Refinery equipment
• Medical devices
• Marine environments, especially those with chlorides present