Stainless steel is used in a variety of applications. It is highly durable, aesthetically appealing, hygienic and easy to clean and maintain. These qualities make it a valuable asset in industries such as transportation, building, research, medicine and food. It also plays a significant role in the manufacturing of kitchen equipment and household appliances, medical and dental tools and instruments, major appliances and vehicle parts, architectural components, and chemical processing, storage and transport equipment.
There are many different grades of stainless steel, but they all share the same fundamental properties: excellent strength and durability, high corrosion resistance, good workability (inability to be welded, formed or machined) and good low and high temperature performance. The differences between the different grades of stainless steel are determined by the alloying elements that are added to the base metal. The grades are identified by a number system that indicates the percentage of each alloying element. Several alloying elements are used in the manufacturing of stainless steel, including chromium, nickel, molybdenum, manganese, aluminum, titanium, copper and niobium.
In order to understand the differences between the various types of stainless steel, it is helpful to know a little bit about the corrosion process that occurs when iron interacts with oxygen in wet and humid conditions. The interaction creates iron oxide, more commonly known as rust. The rust is very brittle, making it easy to remove and leaving the stainless steel behind.
The chromium in stainless steel reacts with the oxide to form a layer of passive film, which prevents further interaction between the iron and oxygen. The passive film can be further enhanced through passivation, a process where the stainless steel is submerged in nitric acid to remove any contaminants that interfere with the formation of the passive film.
When selecting stainless steel for the foodservice industry, it is important to choose a grade that will be resistant to corrosion and heat. There are several options available, including Type 304, which has 18% Chromium and 8% Nickel. It is a versatile stainless steel grade that is commonly used in cookware, cutlery and food preparation equipment. This grade can also be found in sinks, major appliances and surgical instruments, as well as construction materials in large buildings and industrial equipment such as tanks and transport vehicles for chemicals and food products.
Another common option is Type 316, which has an increased percentage of Chromium (22%), plus additional Molybdenum to improve its resistance to corrosion. This grade has outstanding oxidation and corrosion resistance, especially in sulfuric environments. It is also highly resistant to pitting and crevice attack. This grade is a very popular choice for kitchen equipment, pharmaceutical, textile and chemical processing and transport equipment. This grade is also available in a range of forms including sheet, plate, bar, wire and tubing.