Stainless steel is a highly attractive material for use in environments where it will be exposed to chemicals, liquids or foods. All metals oxidise when exposed to air, causing materials such as regular iron and steel to rust. However, the composition of stainless steel ensures that an extremely thin passive chromium oxide layer is created on the surface which then protects the bulk metal from further oxidation. This passive layer is ‘self-healing’ in that if the surface is damaged or removed the passive layer re-forms, protecting the bulk material.
The addition of nickel to stainless steel offers valuable fabrication advantages, such as better formability and weldability, as well as improved corrosion resistance. There are several main groups of chromium-nickel stainless steels and those most commonly used within the pharmaceutical industry are known as ‘austenitic’. An 8–12% nickel content makes them ductile, meaning they can be easily fabricated while remaining tough. Additionally, their 18% chromium level gives them an excellent defence against general corrosion.
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