When selecting stainless steel that must withstand corrosive environments, austenitic stainless steel is often used. Austenitic stainless steels have excellent mechanical properties, and their high levels of nickel and chromium also provide excellent corrosion resistance. In addition, many austenitic stainless steels are weldable and formable. The two most commonly used austenitic stainless steel grades are grades 304 and 316.
304 Stainless Steel
Grade 304 stainless steel is generally considered the most common austenitic stainless steel. It contains a high nickel content, typically 8% to 10.5% by weight, and a high chromium content, approximately 18% to 20% by weight. Other major alloying elements include manganese, silicon, and carbon. The remaining chemical composition is primarily iron.
The high levels of chromium and nickel give 304 stainless steel excellent corrosion resistance. Common applications for 304 stainless steel include:
Appliances such as refrigerators and dishwashers
Commercial food processing equipment
Fasteners
Pipes
Heat exchangers
Structures in environments that would corrode standard carbon steel.
316 Stainless Steel
Similar to 304, grade 316 stainless steel contains significant amounts of chromium and nickel. 316 also contains silicon, manganese, and carbon, with the majority of the composition being iron. The main difference between 304 and 316 stainless steel is the chemical composition, with 316 containing significant amounts of molybdenum; typically 2 to 3% by weight, while 304 contains only trace amounts. The higher the molybdenum content, the more corrosion resistant grade 316 stainless steel is.
When selecting austenitic stainless steel for marine applications, 316 stainless steel is often considered one of the most suitable choices. Other common applications for 316 stainless steel include:
Chemical processing and storage equipment.
Oil refining equipment
Medical equipment
Marine environments, especially those containing chlorides
Food industry