What is Stainless Steel?
Stainless steel is a low carbon steel which contains a minimum of 10,5% chromium by weight. It is this addition of chromium that gives the steel its unique stainless, corrosion resisting properties. The chromium content of the steel allows the formation of an invisible film of chromium oxide on the steel surface. It is this film that creates the corrosion resistant barrier and even if damaged mechanically or chemically, this film is self-healing, provided that oxygen is present. This process is known as passivating. There are numerous grades of stainless steel available and it is important to understand these grades to make an informed decision.
Grade 430 – Has a slightly higher carbon content than type 304 and more corrosion resistant than the lower forms of stainless steel due to the chromium content of 18% and small nickel content (0.75%). Good formability, but with reduced temperature and corrosion resistance. Non-magnetic in annealed form, slightly magnetic when cold formed.
Grade 304 – One of the most widely used and oldest of the stainless steels. This was originally called 18-8 which stood for its chromium (18%) and nickel (8%) content. It possesses an excellent combination of strength, corrosion resistance and formability. It is an austenite steel and is non-magnetic.
Grade 316 – This austenitic stainless steel has an added molybdenum (2%) content to increase its resistance to corrosion. This was originally called 18-10 which stood for its chromium (18%) and nickel (10%) content. This grade of stainless steel comes at a high cost and is expensive for everyday applications. This material is excellent for maritime use.
Stainless Steel Grades Explained: