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The Hard Facts on Stainless Steel - From Penton Media

Issue: April, 2001

Here's what you need to know when buying and caring for stainless steel equipment:

One of the staples of all noncommercial and commercial kitchens is stainless steel equipment. From ovens and mobile heating equipment to mixers and flatware, shiny stainless steel is in abundant supply in today's foodservice operations.

The following is a basic primer on stainless steel as it pertains to the foodservice industry.

Grades, Alloys and Gauges

Stainless steels fall into five classifications according to chemical composition and other properties. The three types most commonly used in foodservice are auestenitic, femitic and martensitic.

Stainless steel is a low carbon steel which contains the alloy chromium at 10% or more by weight This alloy gives the steel its unique corrosion-resisting properties by creating a rough, invisible, oxide film on the steel surface. This film helps increase stainless steel products' longevity and durability because it covers the steel and acts as a shield against corrosion. When nicked, scratched or otherwise penetrated, fresh "passivity" film forms immediately to preserve the steel's surface.

The American Iron and Steel institute designates standard grades of stainless steel by three digit numbers. The austenitic grades employ an 18% chromium/8% nickel alloy. These are the most corrosion resistant, and include both a 200 and 300 series (each series has several grades, such as 310,340, etc.) This steel is most appropriate in severe environments (high humidity, heavy usage). Examples of equipment that typically fall into this category are pots and pans, baking equipment and mixing bowls.

Ferritic and martensitic grades, which contain between 11 and 29% chromium, no nickel and very little carbon, are appropriate in milder environments. These steels generally include numbers in the 400 series (410,420, etc.) Typical products using this grade include cutlery, cooking utensils and some cookware.
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For manufacturers to meet National Sanitation Federation Int'l standards, any stainless steel equipment that comes into direct contact with food must contain a minimum chromium content of 16%. The most commonly used grades that meet this specification are 304 and 430.

The grade of the stainless steel equipment you purchase depends on the price/value relationship given its intended usage. Some high-volume operations may opt for a lower grade product if shrinkage is a big problem.

For the most corrosion resistance, experts advise buying steel that is made from 18/8 alloy; that is, 18% chromium and 8% nickel (some manufacturers offer an 18/10 product). The added nickel (available in grades 304 and higher) helps minimize the possibility of staining, pitting, corrosion, rusting and other forms of discoloration and aids in smoothing out the microscopic grain structure of the metal. That is why 18/8 alloy is used for kitchen counter tops, warewashing equipment and other uses where service is most severe.

Finally, stainless steel products come in a wide range of gauges. The gauge of steel indicates how thick or thin the steel is (the lower the number of gauge, the heavier the steel). The gauge necessary for the equipment you are buying depends on the product's usage. For example, most saucepans are made from 18-20 gauge steel (heavier gauges do not conduct heat as well.)

Cleaning and Care
The best way to extend the life of your stainless steel equipment is to properly clean and care for it. Flatware, for example, should be rinsed, washed and completely dried as soon after usage as possible. However, it is not uncommon for tableware to be left to soak under water for an extended period. Such treatment can easily discolor low-grade stainless over time, especially if the food leftovers contain high levels of salt or acid.

The biggest enemies of stainless steel equipment are mechanical abrasion (steel pads, scrapers, wire brushes), water (especially hard water) and chlorides (in salt and industrial cleaners). Of course, you can't avoid these enemies in your operations, but you can follow these useful cleaning and care tips from the North American Association of Food Equipment Manufacturers (NAFEM).

Always clean stainless steel products with non-abrasive tools. For difficult-to-clean items, use stainless steel pads in the direction of the manufacturers' polishing marks or "the grain."

Use alkaline, alkaline-chlorinated or non-chloride containing cleaners at recommended strength. If you choose to use chlorinated cleaners, be sure to rinse the equipment thoroughly and wipe dry immediately. After wiping equipment down, allow it to air dry. This step will help maintain the stainless steel's passivity film.

Clean stainless steel equipment regularly to avoid build-up of stubborn stains. Be sure to descale equipment regularly with a deliming agent Scaling appears as a white film on steel.

Soften hard water if possible, to help remove corrosive elements that are naturally present in harder-type waters.

Bacteria-free Steel?
While bacteria growth on equipment can't be completely eliminated in a foodservice environment, at least one manufacturer has introduced a special compound that can be applied to stainless steel surfaces to retard the growth of bacteria, mold and mildew. AK Steel recently debuted a FDA- and NSF-approved, natural silver-based product called AgION, an antimicrobial compound that can used in the manufacturing process or can be applied to existing stainless steel surfaces.

©COPYRIGHT 2001 Penton Media, Inc.
©COPYRIGHT 2001 Gale Group