Even if you are a relative newcomer to the foodservice industry, you have heard the term “stainless steel.” But even industry veterans are often undereducated about the finer points of stainless steel and its uses. For such a common material, there is a lot of potential confusion. So let’s get started exploring the finer points of stainless steel and its associated uses.
Table of Contents
- What is Stainless Steel?
- Can Stainless Steel Rust?
- Gauges Explained
- Grades of Stainless Steel Explained
- Specific Steel Types Found in Foodservice Operations
- Is Galvanized Steel the Same as Stainless Steel?
- Cleaning Stainless Steel
What is Stainless Steel?
Stainless steel is not just one thing. It is a term used for a group of iron-based alloys (a metal made by combining two or more metallic elements) that contain a minimum of 10.5% chromium. This combination with chromium is what gives stainless steel its resistance to corrosion. The chromium forms an ultra-thin layer on the steel that is referred to as the “passive layer.” This passive layer is the key to preventing rust and other corrosion.
In addition, the alloy can only have a maximum of 1.2% carbon to be considered stainless. Beyond that, the alloy can contain a number of other elements in varying amounts including nickel, silicon, manganese, titanium, molybdenum, nitrogen, niobium, and others.
Suffice it to say that stainless steel is a combination of metals and other elements. It is the different combinations of these materials that give rise to the different properties of stainless steel.
Can Stainless Steel Rust?
There is a common misconception that stainless steel is some sort of miracle metal that never rusts. This is simply untrue. Because of its chemical make-up, stainless steel is less likely to rust. But it is possible.
You should also be aware that rust is only one type of corrosion. In a restaurant setting, there are any number of chemicals or other substances that can cause corrosion. A common type of corrosion referred to as “pitting” can occur when a stainless surface is not properly cared for or is exposed to corrosive agents for too long. Pitting is just what it sounds like. It appears as tiny pits on the surface of the steel and, left unchecked, can affect both the look and performance of the steel surface.
However, by choosing the right type of stainless steel for your application and applying basic care and maintenance, you can greatly reduce the likelihood of any type of corrosion.
Gauges of stainless steel are the thing that seems to most confuse people. With a lot of things, we think that a higher number is better. So it is natural for people to believe that a higher gauge of steel is better. Wrong!
The gauge refers to the thickness of the stainless steel. Again, you might think that higher numbers indicate thicker steel. But unlike traditional scales, lower numbers indicate thicker sheets of metal. So a 14 gauge stainless steel is vastly more durable than a 22 gauge steel.
Choosing the proper gauge of steel for your application is extremely important. For example, a lighter gauge steel may be perfectly fine for a small hand sink. But for larger, deeper sinks, a heavier gauge steel will be required.
Similarly, as we discussed in our article on equipment stands, you need to understand how you will be using your tables and stands to make the best choice for the gauge of steel required.
Grades of Stainless Explained
While gauge refers to thickness, the grade of steel is a reference to its components and the properties of the steel that arise from using various components. To begin, there are 3 terms you should be familiar with:
Austenitic Steel is the most commonly used grade of stainless. It is composed of chromium and nickel (though some grades may substitute manganese and nitrogen for most of the nickel content). Austenitic steel is non-magnetic (which may be important to you if you use a flatware retriever). It is considered easy to work with and is found in a wide variety of applications in a commercial kitchen.
Ferritic Steel is a magnetic steel that has a low carbon content. It is not as strong or corrosion resistant as austenitic grade. This is the second most commonly used grade of stainless steel.
Martensitic Steel is much less frequently seen in foodservice, this grade of steel is magnetic and is defined by its low level of nickel and moderate level of carbon.
There is a potential 4th category worth mentioning called Duplex. Duplex stainless steels are a more recent addition to the family of stainless steels. As the name might imply, the duplex grade consists of two phases: austenite and ferrite. Duplex stainless steels have not been extensively used in foodservice to date.
Specific Steel Types Found in Foodservice Operations
These different grades have been further defined by the Society of Automotive Engineers (SAE). These grading definitions indicate the composition of the steel, its properties and the standards it must follow.
SAE 304 is the most commonly used grade of austenitic steel. It is typically composed of 18% chromium and 8% nickel (with some manganese thrown in for good measure). Because of this composition, you will sometimes see this referred to as 18/8 steel, especially in reference to flatware. It is highly resistant to corrosion, but it is non-magnetic (again, important if you are using a magnetic flatware retriever). SAE 304 is widely used in the foodservice industry for sinks, work tables, coffee urns, stoves, refrigerators, and equipment stands. It is also used in numerous other smallwares such as cooking utensils, pots, pans, and flatware.
SAE 201 is also an austenitic steel similar to 304 but is less expensive. It provides many of the same benefits as the most expensive 304 grade so it has begun to gain wider acceptance in the foodservice industry.
SAE 430 is an austenitic steel that contains no nickel yet is resistant to corrosion because of its relatively higher chromium content. It is most commonly used for goods that are to be used in lower corrosive environments and conditions. You may see it in lower end sinks and tables but is also sometimes used for panels in refrigerators and ovens.
SAE 316 is a ferritic steel that was originally specified for the medical industry. Though infrequently used in foodservice, it is magnetic and highly resistant to corrosion. Its properties make it more expensive than other steel choices and is more difficult to work with for manufacturers. Therefore it is only seen in specialize products, especially those used in highly corrosive applications.
Is Galvanized Steel the Same as Stainless Steel?
The short answer is no. Galvanized steel is just regular steel that is coated in zinc to prevent corrosion. And as we noted above, stainless steel is the blending of steel with chromium (and other metals) to create a new alloy.
Galvanized steel is weaker than stainless steel. However, it is cheaper and therefore is used in a number of ways in the foodservice industry. For example, you may find refrigerators that are stainless steel on the outside, but only galvanized steel on the inside. While this might be acceptable for some uses, a full stainless steel interior is often preferred for commercial applications as seen in professional foodservice operations.
Cleaning Stainless Steel
As we have discussed, stainless steel is resistant to rust and other corrosion due to its chromium layer. It is important to maintain your stainless pieces to avoid any breakdown of this passive layer that could lead to corrosion. Proper cleaning is essential.
If the stainless piece you need to clean came with instructions from the manufacturer, then by all means follow those instructions. But if you have no other guidance, here are a few simple tips for cleaning your stainless steel.
First, be cautious about using abrasive cleansers. The grit in some cleansers can scratch the stainless surface. This can actually make matters worse as it can lead to further breakdown and ultimately more corrosion.
If you are trying to remove fingerprints or smudges to improve the cosmetic appearance of your stainless, try simply wiping with a soft, dry cloth. You can also try simply using water or a damp cloth as well. Just be sure to dry the surface thoroughly.
If you are trying to remove dirt, grease or other contaminates, you can use a mild detergent (like the one that “takes grease out of your way”). A soft cloth, sponge or even paper towel may be effective. And again, be sure to dry the surface.
You can also try a light vinegar and water solution or a baking soda and water solution to help clean surfaces without chemicals. For more stubborn issues, you may need to use a harsher cleaning agent. You might also need to use a different implement like a scrubbing bristle brush or the scrubber side of a sponge. However, it is always best to test any of these solutions out on a small, less visible area of the piece you are trying to clean. Check for scratching or discoloration. Rinse the surface with water after you use any type of cleaner. And, as always, dry the surface when done.
Avoid metal brushes and things like steel wool as they not only have the potential to scratch the surface, but they can also leave behind embedded particles.
The Final Word on Stainless Steel
As a restaurant or foodservice worker, you will see stainless steel everywhere you look. Understanding the types of stainless steel and their appropriate uses is an important skill as you make purchase decisions. Whether it is a chafer, a sauce cup, a line of flatware or a new piece of equipment like a reach-in refrigerator or a six burner range, stainless steel is found in all aspects of a commercial kitchen.
Have any specific questions about stainless steel? Is there something we didn’t cover that you would like to learn more about? Leave us a comment below and we will try our best to assist!