Stainless steel is a popular material for sinks due to its corrosion and oxidation resistant properties. Steels are a combination of iron and a minimum of 10.5 percent chromium. When the chromium is exposed to oxygen and moisture, such as when a stainless steel object is nicked or dinged, it produces a thin oxide film that coats the product. This self-repairing benefit of stainless steel means that it always looks smooth and shiny and is therefore an ideal material for a kitchen sink. Several European and American metallurgists  make claim to having produced the first stainless steel. Krupp Iron Works in Germany first produced an acid-resistant steel in 1908 and Germans P. Monnartz and W. Borchers discovered the relationship between the chromium content of stainless steel and corrosion resistance. However, one type of stainless steel precursor was patented by American Elwood Haynes in 1911 and a similar material was also developed by English researcher Harry Brearley  at the same time. This resulted in a four-year legal battle during which Haynes successfully blocked Brearley's attempt to patent his version of the steel. Eventually, the pair joined together to form the American Stainless Steel Company. The rest is history and we now can all benefit from the many properties of this versatile material. It is worth bearing in mind that not all versions of stainless steel are the same. Stainless steel can be categorised into four types, which each classified by structure and composition.

Austenitic

The most common variety of stainless steel is austenitic. Items such as cutlery and cookware to automotive trim and industrial applications are generally manufactured from this type, which contains at least 16 percent chromium, no more than 0.15 percent carbon and usually includes nickel or manganese for added durability.

Ferritic

Ferritic stainless steels contain up to 27 percent chromium, as well as aluminum or titanium, although they but have little or no nickel.  The result is that, this type, whilst resistant to corrosion, is not so durable as austenitic stainless steel. Ferritic steels are less expensive than austenitic varieties and are commonly used for kitchen sinks.

Martensitic

This variety is less corrosion resistant than austenitic and ferritic but extremely strong and durable. It comprises 12 to 14 percent chromium, along with small amounts of molybdenum (0.2 to 1 percent) and carbon (0.1 to 1 percent). It has little or no nickel (less than 2 percent). Martensitic stainless steels are magnetic and  therefore very useful for products such as kitchen backsplashes or spice racks as they can be attached easily.

Duplex

Duplex stainless steels combine the benefits of austenite and ferrite to form a durable stainless steel with enhanced decay resistance. Metallurgists often like to create a mix that is half austenitic and half ferritic to form a material that features more chromium and less nickel than is found in pure austenitic steels.These steels are primarily used in chemical plants and pipework.

How stainless is stainless?

Whilst stainless steel is highly resistant to discoloration and blemishes, it is not entirely impenetrable. Although stainless steel is extremely durable, it is still possible for the protective layer of film covering a stainless steel item to break down over time, resulting in corrosion and pitting. Chemicals such as chloride and hydrogen can also cause the film to crack. The level of rust resistance of a particular steel depends on its composition. More chromium means more corrosion protection. The strongest stainless steels also contain at least 8 percent nickel. When investing in stainless steel items, it is important to understand that some metals advertised as stainless steel are actually stainless steel plated.  This means that the plate is corrosion-resistant but susceptible to damage if it receives scratches deep enough to reach the underlying material. The plate can also wear off over time. Stainless steel also needs to be cleaned regularly. Generally, soap and water will be sufficient but, for tougher stains, a variety of household remedies can be used. A couple  of drops of olive oil or window cleaner will get rid of most fingerprints and smudges, whilst white or cider vinegar will bring back shine. Never use steel wool pads or harsh cleansing powders on stainless steel as they will scratch the surface. To remove burnt-on food from stainless steel saucepans, soak them in warm water and then clean with baking soda and a nylon scouring pad.