Stainless Steel is an alloy containing mostly iron, and at least 10.5% chrome. Additional alloying elements of Copper, Molybdenum, Titanium and Nickel are added in varying amounts to provide strength, toughness and to provide additional corrosion resistance to salt chemicals and also cold working ability. Non-metallic elements such as Carbon and Nitrogen are also added.

As a general rule, the higher the chromium content of stainless steel the higher the corrosion resistance. When nickel is added to create the austenitic steel the oxide film is strengthened and increases the durability in more aggressive environments. If molybdenum is added to either austenitic or ferritic stainless steel the pitting and corrosion resistance is greatly improved.

Stainless Steel is divided into four main groups:

Austenetic

Typically 18% Chrome with 8-12% Nickel, these grades are non magnetic and are used extensively in the petrochemical, catering and marine industries.

Feritic

13-17% Chrome with a low carbon content, these grades are magnetic and cannot be hardened by heat treatment

Martensitic

Typically 12% Chrome with a higher carbon content than the feritic types. Also magnetic but can be hardened by normal quenching and tempering techniques. Commonly used in the production of cutlery and also in the aerospace industry.

Duplex Stainless

Used where both strength and corrosion resistance is needed. Cannot be hardened by heat treatment. The metallic structure is a combination of austenite and ferrite.