Aluminium vs steel contraction when frozen

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What is Stainless Steel?

Stainless steel is made up of iron, chromium, nickel, manganese, and copper.  This iron alloy has a minimum of 10.5 percent chromium, an agent that provides corrosion resistance.  It’s non-porous and non-corrosive with higher resistance to rust as well.

What makes stainless steel less corrosive is a “passive” layer of chromium oxide that the chromium forms.

Vollrath explained this is 12 to 30 percent chromium and too thin to be visible but protects the metal beneath.  Nickel assists in the process and restores itself with oxygen. So—as long as the passive layer or film stays intact, isn’t broken or contaminated, a product remains stainless.

But can it still stain? Yes. A scratch to the surface can lead to rust. So can heated water that leaves deposits and chlorides found in salt, water, cleaner and quaternary salts.  But even though the possibility to stain is there, Vollrath reminded us it’s called stainless because it won’t rust, corrode or rust as easily as ordinary steel.

Types of Stainless Steel

Austenitic Stainless Steel

Comprised of alloy with nickel and chromium.  There are the 200 and 300 series stainless steels and are the most specified grades in foodservice.  Austenitic stainless steels are corrosion and water resistant.  They are non-magnetic as well.

200 series: In general, this type of stainless steel is commonly used for wheel covers and door hardware.  Being more specific to the foodservice industry, these are commonly found in counters, oven parts, covers and tray slides.

300 series: These are typically found in steam table pans, sinks, food processing equipment, and Bains Marie.  The 300 series contains 301 and 304 stainless steel.

• 301 stainless steel is 17 percent chromium and 6 percent nickel (otherwise known as 17/6).  As there is less nickel, it isn’t as corrosion resistant as 304, however, Vollrath said it is more difficult to form and is stronger because it has less nickel.
• 304 stainless steel is 18 percent chromium and 8 percent nickel (otherwise known as 18/8). It resists most oxidizing acids and is very corrosion resistant.

Ferritic Stainless Steel

This type of stainless steel does not contain nickel and does not have the same corrosion resistance found in the 200 and 300 stainless steel. It’s also magnetic.

400 series: In general, type 430 stainless steel (explained more in detail below) is found in automotive trim, architecture, and mufflers.  Specific to the foodservice industry, this type is common in flatware, carts, structural parts, and steam tables.

• 430 stainless steel is 16 to 18 percent chromium and contains no nickel (otherwise known as 16/18-0).  Despite not having any nickel, it is quite corrosion-resistant but not as much as the 300 series.

What Is the Difference Between Stainless Steel Gauges?

In addition to series, stainless steel gauge is another factor that will determine the durability of your stainless steel equipment. Common gauges include 14, 16, 18, 20, and 22 gauge. The lower the gauge, the thicker the stainless steel, which means it’ll be much more durable – and also more expensive. Therefore, a 16 gauge stainless steel equipment will be able to put up with more of the crazy demands of high volume rushes, and typically last longer, than a 20 gauge piece.

Is Stainless Steel Magnetic?

Some stainless steel is, while others are not. So, which types of stainless steel are magnetic? Ferritic stainless steel is traditionally magnetic while austenitic stainless steel is not, given ferritic’s much higher concentration of iron in its construction process. Therefore, magnets won’t work on all types of stainless steel.