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It wasn’t until the early 20th century, after several years of experimentation, that a perfect combination of chromium and carbon produced the stainless steel product used today. An English scientist, Harry Brearley, is the one credited for creating the perfect combination of steel with 12.8 percent chromium along with 0.24 percent carbon. His discovery has been acknowledged as being the first ever evidence of stainless steel.
The popularity of stainless steel fixtures in home kitchens and commercial ones boils down to the fact that it is easily maintained and, even after years of use, keeps its shiny, clean look. The benefits of having stainless steel in commercial kitchens are extensive. Durable, nonporous and more resistant to corrosion than most other materials makes it perfect for food preparation areas. Maintaining the sparkling shine and keeping rust at bay is the key to a long-lasting appliances, countertops and sinks.
An iron alloy made up of different amounts of carbon, manganese and silicon, stainless steel includes a thin oxide layer, called the passive layer, produced by the chromium additive in different strengths giving extra resistance to corrosion. Nickel and molybdenum are also added at times resulting in different grades. There are five types of stainless steel from which to choose:
Austenitic – The most common type with nickel, nitrogen and manganese added making it stronger and more resistant to stress corrosion cracking. Non-magnetic.
Ferritic – The best choice for commercial kitchens or seaside use due to small amounts of carbon added to chromium making it perfect for high-pressure conditions. Magnetic.
Duplex – A combination of 50 percent ferritic and 50 percent austenitic for more strength and improved resistance to stress corrosion cracking than either one separately. Magnetic.
Martensitic – A higher carbon addition, yet similar to ferritic type, makes it easier to harden and temper. Moderate corrosion resistance. Magnetic.
Precipitation hardening (PH) – Greater durability and heat resistance is created by adding elements like aluminum, niobium and copper. Same resistance to corrosion as the austenitic type.
According to the British Stainless Steel Association (BSSA), the fact remains that stainless steel doesn’t mean it won’t corrode or rust. These problems usually stem from aggressive usage (like in commercial kitchens), scratches from implements or leaving tools on wet surfaces. The the thin layer that generally protects from ‘basic’ corrosion can be damaged and rust or corrosion appears. Common forms of corrosion damage are:
Pitting corrosion – Chloride ions found in salt and bleach coming in contact with the passive layer over a prolonged period of time. It can be avoided by eliminating exposure to harsh chemicals that include chloride or using a more resistant grade of stainless steel.
Crevice corrosion – Oxygen assures that the passive layer forms on the stainless steel surface. Sometimes the oxygen doesn’t reach the entire surface leaving some areas vulnerable. Sealing the crevices with sealant can keep this from happening or use a more resistant grade of stainless steel.
General corrosion – Some acids, like hydrochloric or sulphuric, may attack the passive layer causing an overall corrosion. This doesn’t usually happen with stainless steel as much as it does with simple carbon and alloy steels. It all depends on the temperature and concentration of the chemical exposure. Check with the manufacturer if unsure.
All the grades of stainless steel require the same level of care. It is easy to do but must be done regularly. Simply washing with a mild detergent using warm water and non-abrasive cleaning tools is enough for most surfaces. Helpful hints to keep in mind:
1. Removing any food and water deposits from surfaces with a soft sponge or microfibre cloth is the most important step and must be done often. Scratches from metal scrapers, abrasive brushes or steel wool pad damage the thin protective layer leaving the surface vulnerable to rust or corrosion.
2. The next step should include using a stainless steel cleaner that has an alkaline or alkaline-chlorinated solution in it as opposed to the traditional chloride. If using chlorine is the only option, check the concentration and rinse off quickly. Make sure all bits of food and food stains are removed.
3. Finally, a good quality stainless steel or metal polish should be applied with a soft cloth. A good rule to follow is wiping with the grain of the steel surface and not up and down.
If the stainless steel surface is showing discolouration, maybe from neglect or misuse, other methods need to be implemented. Some cleaning challenges and suggestions include:
In the commercial kitchens, several factors affect the choice of stainless steel for sink units. The most important is the fact that it is extremely hygienic, so preparing food safely with the knowledge that food poisoning by cross-contamination is not an issue. The most common food grade alloy choice is called 304 stainless steel. It is easy to clean and maintains its original look longer. Remaining durable with aggressive use in busy kitchens and relatively inexpensive all over the world make it easier to replace if needed. Commercially, stainless steel is the product to use and will remain in the forefront of recommendations for long-lasting satisfaction. Check with suppliers and manufacturers for more information.