Metals in Foodservice

Food grade metal is everywhere you look in a restaurant, from the stainless flatware in the dining room to carbon steel pans and aluminum-sided equipment in the kitchen. Each metal's unique properties make it better suited for certain applications than others. Below, you'll find an explanation of the types of food-grade metals used to build foodservice equipment and how to care for them. In this food safe metals list, we'll also discuss the agency standards that govern foodservice metals, specifically NSF 61 and NSF 51.

Sanitation and Safety Standards for Foodservice Metal

The same way the NSF certifies certain types of foodservice equipment to be easy to keep clean and sanitary, it certifies certain materials used to make that equipment safe for food contact. Two NSF standards are directly concerned with the materials with which foodservice equipment is made:

NSF Standard 51 defines which types of materials, including metals and finishes, are considered safe to contact food.¹ These criteria are intended to ensure that equipment and supplies are easy to clean and sanitize, and pose no risk of transferring harmful substances to food that contacts them.

NSF Standard 61 regulates any material that holds or touches drinking water at any point.² This includes pipes, fittings, faucets and other fixtures, sink basins, and other containers. As with NSF 51, this standard is intended to prevent unsafe chemicals, particularly lead, from getting into consumers' food and drinks.

Is Stainless Steel Food Safe?

The most common food grade metal is stainless steel, which is popular owing to its rust resistance and the fact that it's easy to clean. Whereas regular steel is made primarily of iron and carbon, food-safe stainless steel is an alloy of iron and chromium. Nickel is usually thrown into the mix to increase the metal's hardness, and more exotic elements like molybdenum sometimes are used to create steels for specialty applications.³

Stainless steel is strong, sanitary, and attractive. It resists rust, scratching, and denting extremely well. It's popular in foodservice for its ability to undergo a fair amount of abuse without being damaged – a property that makes it the number one choice for building restaurant equipment. Stainless steel also can withstand moderate levels of exposure to moisture, chemicals, and food without corroding or pitting, so it's a natural choice for work tables, pots and pans, and other equipment that may interact with food.

Steel must be at least 11 percent chromium to be called stainless, and it’s the inclusion of that element that makes steel resistant to rust.⁴ Chromium allows the outer layer of steel to bind with oxygen to form what's called a passivation layer: an invisible film that prevents steel from rusting as easily. Due to the metal's composition, this passivation layer is self-repairing if the metal becomes scratched or nicked.

You'll find several types of food-safe stainless steel being used in foodservice equipment. The differences between the types come down to the elements used to make them and the ratio of each. You may encounter two different rating systems used to describe the different types of stainless steel on the food-safe metals list. When you're dealing with equipment and fabricated fixtures, you'll most likely see the SAE (Society of Automotive Engineers) ratings used to describe steel.⁵ Two SAE steel grades are common in foodservice:

300-series stainless steel is made with chromium and nickel, usually 18 percent and 8 percent by mass, respectively. Steel in this series is austenitic, which describes how the alloy's molecules are arranged into their crystal pattern. That arrangement makes most austenitic steels non-magnetic.⁶
400-series steels contain chromium, and tiny amounts of nickel and other elements. Because of that molecular makeup, 400-series steel is arranged into a ferritic or martensitic crystal pattern and will always attract a magnet.⁷

Stainless Flatware Grades

When you're shopping for flatware or similar utensils, you're likely to encounter a different steel grading system which describes how much chromium and nickel are present in each type of steel. This system can be used to determine a piece's durability and ability to hold a shine.⁸

Composed of 18 percent chromium and no nickel, 18/0 steel is used to make economy flatware. It tends to have a dull finish, especially after it's been used and washed repeatedly. Utensils made of 18/0 steel bend more readily than premium flatware.
Made with 18 percent chromium and 8 percent nickel, 18/8 steel is shiny and resistant to bending and rust, but it can lose its sheen over time. Flatware made of 18/8 steel is a good middle-of-the road balance between cost and longevity.
The highest-quality all-stainless flatware available, that made of 18/10 steel, includes 10 percent nickel, which makes it easy to keep polished and highly resistant to rust and bending. The higher level of nickel makes 18/10 steel flatware pliable during manufacturing, so flatware made with it can have more intricate patterns.

For a thorough discussion of stainless steel flatware, see our Flatware Buyers' Guide.

Taking Care of Food Safe Stainless Steel

Stainless steel equipment can last for years and even decades when it's cared for properly. Follow these maintenance tips to get the best results from your stainless steel equipment and supplies:

Make sure stainless steel is rinsed thoroughly after it's washed to remove chemicals from detergents that can prematurely wear down the metal.
A mixture of baking soda and water can be used to clean and polish food safe stainless steel gently.
When you clean and scrub a stainless steel surface, do so along the steel's polish lines, or "grain," to prevent creating scratches that can damage the equipment's surface.
Avoid using steel wool and wire brushes to clean stainless steel. Metal cleaning tools can scratch steel's surface, creating a rough exterior that can pit and degrade over time.
Avoid exposing steel to substances that contain chlorine, high levels of salt or acid, or corrosive solutions found in certain cleaners. Use non-chlorine cleaner only and rinse steel thoroughly after it makes contact with a substance containing chlorine.
Prevent hard water deposits, as they can play a role in causing rust. Take measures to clean your equipment regularly to keep deposits to a minimum. If your water supply is especially high in minerals, consider installing a treatment system that softens the water on its way to your equipment.

Is Aluminum Food Safe?

The second most commonly used metal on our food-safe metals list is aluminum. Aluminum is less expensive than stainless steel, but it's also softer and able to withstand less abuse. Food grade aluminum is used for its light weight, low cost, and rust resistance, and is prized in cookware for the speed with which it heats.⁹ As with steel, the aluminum used to build restaurant equipment is alloyed with other elements to give it strength and durability. There are three main types of food grade aluminum used to build restaurant equipment and kitchen supplies, each of which includes the addition of manganese, silicon, iron, and/or copper. The percentages present in each of those elements determine a grade's physical properties.¹⁰

The softest type you'll find in foodservice is 1100 aluminum. Its softness makes it easy to form into a variety of shapes, but leaves the material prone to scratching, warping, and denting.
The higher concentration of manganese in 3003 aluminum makes it harder, more durable, and ideal for medium-duty cookware. This formulation produces aluminum with moderately increased strength and hardness, but undiminished ductility, so it can be used in many applications.
The heaviest-duty aluminum used in foodservice is 3004 aluminum, which is made with at least 1 percent manganese and about as much magnesium. The addition of magnesium increases the metal's solid solution strengthening and strain hardening ability, making this type of aluminum extremely hard and not very flexible or ductile.

Applications for Food Grade Aluminum

Aluminum often is used for exterior parts of equipment that aren't exposed to abuse, such as the sides and backs. It can be finished to match surrounding stainless steel for a uniform look. Another advantage to aluminum is that, if the passivation layer ever is damaged, it gradually rebuilds itself.

Economy cookware is made from aluminum for its low cost, light weight, and ability to heat quickly and evenly. See our article on cookware materials for a deeper discussion of aluminum and other types of cookware.

Aluminum-containing substances also may be added to ceramic to make china. Feldspar, also known as aluminum silicate, is added to the clay body to make china stronger, enabling pieces to be made very thin without becoming fragile.¹¹

Anodized aluminum is finished with a process that thickens and strengthens its passivation layer, making it extremely hard and scratch resistant, as well as more resistant to corrosion. That process often coincides with dyeing the metal's surface to add a decorative sheen.

Caring for Food Grade Aluminum

Aluminum may be softer than steel, but with a little effort, it can last for many years. Follow these care and cleaning tips to extend the lifespan of your aluminum equipment and kitchen supplies:

Mildly acidic substances, such as vinegar, lemon juice, and cream of tartar, work to remove stains from aluminum surfaces.
Avoid using steel wool and metal brushes that can scratch the soft metal and create a rough surface that food is prone to stick to.
Avoid exposing aluminum to salt and chemicals that contain chlorine, which can cause the metal to pit.

Manufacturing Methods

Manufacturers employ a few methods to form metals into the final components used to build restaurant equipment. Like the different materials on this food safe metals list, each one of these manufacturing methods has benefits and drawbacks.

Casting is the process of pouring molten metal into a mold and allowing it to cool to form the desired shape.¹² This is the process that gives cast iron its name. Cast pieces tend to be dense and heavy, so casting is the ideal process for creating heavy-duty components such as burners, grates, and handles for charbroilers and ranges.

Bending involves folding sheet metal along straight edges to form it into simple shapes.¹³ This process is widely used to form panels for cooking equipment, dish cabinets, and fixtures such as tables.

Deep drawing is the process of using a punch to push a piece of sheet metal through a die to form a shape.¹⁴ This is a popular method for forming containers like steam tables pans and sink bowls, and is especially beneficial when sanitation is a priority because

Stamping involves cleanly cutting two-dimensional shapes out of sheet metal.¹⁵ This process is used to press out components like brackets for fixtures and sometimes is used to form the blades of economy knives.

Other Food Grade Metals

While stainless steel and aluminum are by far the most popular FDA food safe metals used in foodservice, a few other materials play important roles in the industry.

Cast iron is a simple alloy of iron and carbon that's used to form rugged, heavy components including gas burners, grates, and radiants. Cookware is the most well-known application for cast iron outside the commercial kitchen, but restaurants do occasionally employ cast iron servingware to provide a rustic tabletop presentation.
Copper is a metal that's prized for its superior ability to conduct both heat and electricity. All electric equipment includes copper wire circuits, and copper cookware is common in high-end restaurants, especially where kitchens are open and customers can see the attractive metal.
Galvanized steel is a type of economy steel that that has been treated with a coating of zinc to make it impervious to rust. Galvanized steel often is used to build the bottom panels of cooking equipment, legs and support components of economy work tables, restaurant dining tables and chairs, and to form utility containers, such as serving baskets and pails and trash cans.

References

Food Equipment Materials: American National Standard/NSF International Standard 51. NSF. Accessed October 2021.
NSF Standard 61: Drinking Water System Components. NSF. Accessed October 2021.
Metallurgy of Mo in Stainless Steel. International Molybdenum Association. Accessed October 2021.
5 Common Alloying Elements. Metal Supermarkets. Accessed October 2021.
AISI/SAE Steel and Alloy - Designation System. The Engineering Toolbox. Accessed October 2021.
Difference Between 300 Series And 400 Series of Stainless Steel. Ambica Steels LTD. Accessed October 2021.
Metal Spinning Stainless Steels (300 and 400 Series). Helander Metal. Accessed October 2021.
Different Types of Stainless Steel. TFG USA. Accessed October 2021.
Characteristics, Applications, and Properties of Aluminum. Dielectric Manufacturing. Accessed October 2021.
Aluminum Alloys and their Classification. Mississippi State University. Accessed December 2022.
How Products are Made: Porcelain. How Products Are Made. Accessed October 2021.
The Metal Casting Process Explained. General Kinematics. Accessed October 2021.
What is Metal Bending. Salamander Fabrications, LTD. Accessed October 2021.
What is Deep Drawing and How Does the Process Work. Stamping Simulation. Accessed October 2021.
Understanding Metal Stamping. Thomas Net. Accessed October 2021.