Stainless Steel Grades and Classification

The two most commonly produced grades of stainless steel are 304 (known as 'A2') and 316 (known as A4). Both of these grades will offer excellent corrosion resistance, cleanability, and the ability to handle extremely low (cryogenic) and high temperatures.

Grade 316 is also known as marine grade stainless steel due to its increased resistance to chloride corrosion compared to type 304.

The basic chemical compositions of these two grades are as below:

Grade 304 stainless steel (A2): chromium 18% + nickel 8% (known as '18/8')

Grade 316 stainless steel (A4): chromium 18% + nickel 8% + molybdenum 3% (known as '18/8/3')

Stainless steel can also be classified by their crystalline structure, which is determined by their chemical composition. The two grades mentioned above are Austenitic stainless steels. Other types include Ferritic, Martensitic, and Duplex.