Difference between 304 and 316 Stainless Steel

The stainless steels are used in most metal applications because of their strength, corrosion resistance and cost effectiveness. There are ferritic, austenitic and duplex stainless steels. The 304 and 316 steels are austenitic stainless steels. They are both 18% chromium and 8% nickel in the composition. The 316 material has molybdenum in the composition. The 4% molybdenum allows the 316 material to have high corrosion resistance against chloride ion. Both materials have carbon, iron, manganese, phosphorus, sulfur and silicon in the composition. They both have 8grams per centimeter cube densities. The 304 material is much easier to machine than the 316 material.

The 304 vs 316 stainless steel machinability is favorable for the 304 material. It could be formed and machined. It is easy to clean for strains. While the 316 is hard to machine and hard to clean it does not catch rust and other surface corrosion easily. These reasons serves differently in different applications. The regular domestic and low cost applications use 304 due to the cost efficiency and easy to clean features. The 316 is used in sea water, marine and food grade applications because of the high corrosion resistance. However, the 316 material is more expensive than the 304 due to the molybdenum addition in the content. The 316 material is also harder to form. So the use of 316 is preferred only in applications where the 304 cannot be used. However, 304 material can replace the 316 material wherever possible. The 304 316 stainless steel magnetic properties are similar but the 316 has less magnetic properties compared to the 304 material.

The magnetic property of these materials is mostly because of the magnetic properties of nickel in the composition. Both these materials can be subject to particle separation in the face of powerful magnetic separators in the process flow systems. These cause the materials to disintegrate into small particles which could be attracted towards the magnetic field. The use of 316 material instead of the 304 material in high corrosive and food grade production systems reduce the risk of the particle attraction happening due to the magnetic fields. It is often a problem how to check ss 304 and 316 to confirm which material it is. Material check reports are the best way to check and confirm the material.

The are both similar when they are out of the factory. It is hard to visibly recognize them from each other. A clear inspection for rust can reveal the difference. The electrical resistance of 304 is higher than the 316 material. If you have some means of measuring that, you can differentiate them. For people who do not have much technical knowledge or resources, the easiest way is to have a rust test. The 304 material rusts in sea water and the 316 doesn’t. The sea water has sodium chloride. To replicate the effect, dipping the material in sodium chloride or kitchen salt solution. The 304 material will develop stain or rust while the 316 material won’t.

find out 304 vs 316 stainless steel machinability and magnetic properties