Selecting the Right Stainless Steel Grade for Food Processing Equipment
When it comes to food-grade fabrication, choosing the correct materials is important in ensuring safety, durability, and cost-efficiency. At Metalbook, we recognize the importance of high-quality materials, especially with food-grade applications. In this post, we have outlined a few of the reasons as to why stainless steel is the preferred material for food-grade fabrication and how it can benefit your projects.
Introduction
Stainless steels are commonly used in food and beverage manufacturing and processing applications. These applications include manufacture, bulk storage and transportation, and preparation and presentation. Stainless steel refers to a class of iron-based alloys that have a combination of, at minimum, 11% chromium. The alloy includes variations of metals, mainly nickel, and additional elements, in particular, carbon. Additionally, the baby's elemental makeup gives stainless steel the attributes that benefit many industries, particularly those that involve the finished metal being placed in aggressive or challenging environmental circumstances.
In the food industry specifically, stainless steel is subjected to heat, water, and harsh cleaning chemicals. Through those exposures, stainless steel grade used in the construction of equipment and appliances needs to endure a rust/corrosion-free state and be sanitized quite easily. Also, because it has pitting-resistant properties, it reliably has a surface that is easy to keep clean and maintained well, and the heat resistance of the metal means it is reliable in handling extremely high temperatures without risking damage.
For these reasons, many food manufacturers use stainless steel metal trays in their food-making processes. However, some may not realize that there is not one kind of stainless steel. There are hundreds of types of stainless steel, and each will have its specific mix of properties.
Which stainless steel is best depends on how the stainless steel will be used. For example, a confectionary manufacturing chocolates is going to have performance needs that are incredibly different from that of a processor who is specializing in tomato sauce.
Stainless Steel Features & Benefits for the Food Industry
Stainless steel is a material of choice for food handling applications for many reasons. The material can endure extreme temperatures, and its protective oxide layer protects against rust that could leach into food and otherwise cause contamination. One of the most important characteristics of food-grade stainless steels is that they do not contain dangerous chemicals that could be absorbed into foods.
Other features and benefits that make stainless steel a good choice for the food industry include:
- Great corrosion resistance
- Extreme strength
- Ease of cleaning
- Non-reactive surface
- Low maintenance costs
- Impermeable surface to prevent contamination
- Available in various finishes
- Chemical and bacterial neutrality
- Made to handle frequent cleanings with harsh detergents
- Does not retain or transfer food smells
Choosing the Best Stainless Steel Food Grade for Your Application
Although there are many different kinds of stainless steel, there are only a few varieties considered food-grade. The vast majority of food-grade stainless steels come from the 300 series and 400 series types, including:
- Food Grade Stainless Steel 316 is an austenitic stainless steel alloy with increased chromium and nickel content, ideal for food applications, and has great resistance to acids, alkalis, and chlorides. Its continuous-use temperature is many times higher than what most food-making processes use; it is also suitable for many more applications.
- Grade 430 stainless steel offers a level of stainless steel very similar to grade 316, but it has only a small amount of nickel, making it a low-cost alternative for some food makers. It is also a ferritic alloy, which means that it is magnetic by default, and its resistance to stress corrosion cracking is fantastic.
- 304 Grade Stainless Steel is economical and offers ease in sanitizing and great weldability and formability while used in food processing environments. Typical uses include storage tanks, fermentation vats, and dishwashers.
- 316 Grade Stainless Steel is an austenitic iron alloy containing relatively high amounts of nickel and chromium; it is well-suited for food handling processes and is capable of being used at temperatures well above the maximum temperature needed for food handling operations. 430 Grade Stainless Steel is used in food processing; it is equivalent in chromium content to grade 316 and has much less nickel content which makes it a better choice for most food processors.
- The '316' grades (1.4401/1.4404) are referred to as the 'food' grades; however, no official designation is known. The common grades 1.4301 and 1.4016 may also be suitable for food processing and handling, but due to low nickel content, they are not as resistant to some dilute reducing acids as grade 316 stainless steel.
Typical applications of the various stainless steel types
Types | Typical Applications |
420, (martensitic) | Cooks and professional knives, spatulas etc |
430, (ferritic) | Table surfaces, equipment cladding, panel, (i.e. components requiring little formability or weldability). Used for moderately corrosive environments, (e.g. vegetables, fruits, drinks, dry foods, etc). |
304, (austenitic) | Vats, bowls, pipework, machinery parts, (i.e. components requiring some formability or weldability). Corrosion resistance superior to 430. |
316, (austenitic) | Components used with more corrosive foods, (e.g. meat/blood, foods with moderate salt contents), which are frequently cleaned, with no stationary solids and not under excessive stress. |
1.4539, (austenitic) | Used with corrosive foods, (e.g. hot brine with solids that act as crevice forms, stagnant and slow moving salty foods). |
1.4462 (duplex) | Used with corrosive foods, (e.g. hot brine with solids, stagnant and slow moving salty foods). Higher strength than austenitics. Good resistance to stress corrosion cracking in salt solutions at elevated temperatures. |
6%Mo. types (austenitic) | Used with corrosive foods, (e.g. hot brine with solids, which act as crevice formers, stagnant and slow moving salty foods). Good resistance to stress corrosion cracking in salt solutions at elevated temperatures. Used in steam heating and hot work circuits, hot water boilers, etc |
Common Applications
Various applications within the food and beverage industry depend on food-grade stainless steel. Stainless steel is preferred over other materials in the following applications:
- Beer kegs
- Confectionary equipment
- Conveyor systems
- Double-wall transport containers
- Evaporator tubes
- Flour silos
- Food mixers
- Food pulverizers
- Ice cream molds
- Industrial ovens
- Peeling machines
- Syrup tanks
- Tanks holding dairy
Which is Best for Food-Safe Applications?
On balance, grade 316 is generally a better option for food-grade stainless steel containers. 316 SS is more chemically resistant in multiple applications, and especially when exposed to salt and stronger acidic items such as lemon and tomato juice.
However, 430 does serve as a good, lower-cost option for food manufacturers that only require a moderate resistance food grade steel sheet as part of their making process.
It's important to remember that the resistance properties of both alloys can be improved with electropolishing. This process enhances the oxide layer that protects the steel, but it also removes small peaks and valleys in the surface of the alloy, which makes it more difficult for food to stick to the steel and easier to clean.
However, it's also important to remember that the upkeep of a custom stainless steel tray or basket also plays a huge role in prolonging its useful life. For example, stainless steel sheet metal should never be scrubbed with a plain steel or iron brush, as this can transfer iron particles to the surface of the stainless steel and disrupt the protective oxide layer.
With the right stainless steel alloy, you will have a metal tray or basket that will enhance your productivity for years to come! Are you in need of a custom metal form for your food production process? Contact Metalbook today!
