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Stainless steel is all the same, right?

Stainless steel is all the same, right? Wrong. There are many different types of stainless steel and at least three different types are used to construct commercial refrigeration equipment. Make the wrong choice and your gleaming new unit could become a rusting hulk, unfit for your kitchen. We give you the knowledge you need to make an informed choice.

Three types of stainless steel are generally used in commercial refrigeration i.e. 200-series, 300-series and 400-series.

For steel alloy to be classified as ‘stainless steel’ it must contain a minimum of 10.5% chromium. Chromium reacts with oxygen and moisture in the environment to form a protective, adherent and coherent, oxide film that envelops the entire surface of the material. This oxide film (known as the passive or boundary layer) on stainless steels exhibits a truly remarkable property: when damaged (e.g. abraded), it repairs itself as the chromium in the steel reacts rapidly with oxygen and moisture in the environment to reform the oxide layer.

What does that mean? It means it protects the metal against corrosion. Increasing the chromium content gives it more protection and corrosion resistance may be improved even further by adding 8% or more nickel. As you can see, in a commercial kitchen you will want your equipment to be constructed from stainless steel containing more than 10.5% chromium and 8% nickel to resist corrosion in that humid environment. The solution, generally only available from the best manufacturers, is '18/8', a high-grade stainless steel. It is used in the construction of only the highest quality commercial refrigeration equipment. It gets its name because it contains 18% chromium and 8% nickel. It is widely known as '304' (in the American AISI grade designation system) or 1.4301 in the European BS EN 10088 standard. It is identifiable by the fact that it is not (or only very weakly) attracted by a magnet.

A cheaper alternative, increasingly used because it is antimagnetic like ‘304’ and so much more difficult to detect is ‘200’-series which contains 16%-18% chromium and some nickel, but in significantly lower proportions.

'18/0' stainless steel, known as '430' in the AISI system or 1.4016 in the European standard, is used as another cheaper alternative. It is only really suitable in instances where corrosion resistance is less essential, like ‘front of house’ display refrigeration. It is distinguishable because it is attracted by a magnet (like pure iron).

Are you getting value for money? We suggest you take a long hard look at the specification of the commercial refrigeration equipment currently available. As a rule, if it doesn’t say it’s made from ‘304’ stainless steel then it probably isn’t. At least one well-known and well-established brand offers the option of ‘304’ stainless steel as the interior and exterior material on some of its models but they cost more than twice the price of the standard, lower quality, model and almost three times as much as the cost of the AXIS equivalent model. All AXIS commercial refrigeration is constructed from high-grade ‘304’ stainless steel as standard. Make your own comparisons and draw your own conclusions.

Source: Includes extracts and content adapted from the ‘Stainless Steel Family’ by the International Stainless Steel Forum.