304 vs. 316 Stainless Steel
Stainless steel is one of the most popular and well recognized metals, known for its attractive appearance, low maintenance requirements, and resistance to corrosion and staining. Unlike regular carbon steel, stainless steel does not readily corrode in the presence of water. When the strength and toughness of steel are required, along with the need for corrosion resistance, stainless is often the answer.
Steel is an alloy, a combination of several metals. Steel always contains iron and carbon, along with small percentages of other elements. The amount and type of elements that are added during fabrication result in many different classes and grades of steel. So, for example, all types of stainless steel contain at least 10% chromium by weight.
When exposed to air and moisture, the iron in most steels will rust, creating an active iron oxide film that accelerates corrosion by continuously forming more iron oxide. The large amount of chromium present in stainless reacts to form a film of chromium oxide on the surface. This passive film prevents further corrosion on the surface, while also blocking its spread into the metal’s internal structure.
Different grades and surface finishes of stainless steel are made to suit different applications and environments. The most common types of stainless steel are alloys 304 and 316. Both are austenitic stainless steels, which means they are non-magnetic and easily worked.
304 Stainless Steel
The most versatile and widely used of all stainless is grade 304 stainless steel, also known as A2 or “18/8” stainless because it contains 18% chromium and 8% nickel. This stainless grade provides the best all-around performance due to its chemical composition, mechanical properties, weldability and oxidation resistance. As a result, 304 stainless is available in a wider range of products, forms and finishes than any other stainless steel.
Stainless steel 304 can be easily brake- or roll-formed into a variety of components for applications in industry, architecture, and transportation. The balanced austenitic structure of grade 304 stainless enables it to be severely deep drawn without intermediate annealing. As a result, 304 is dominant in the manufacture of drawn stainless parts such as sinks, hollow-ware and saucepans.
Other well-known uses of 304 stainless include kitchen appliances, cutlery, surgical instruments, and industrial equipment. It is also commonly used in commercial kitchens and food processing plants because it can be steam-cleaned and sterilized and does not require paint or other finishes.
304 Pros: Strong, low-cost, easily formed and welded, readily available in many forms, resists stains and corrosion.
304 Cons: Not fully resistant to corrosion & pitting in acidic chemical or marine environments.
316 Stainless Steel
Grade 316 stainless steel is the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The significant percentage of molybdenum (2-3%) gives 316 better overall corrosion resistant properties than grade 304, particularly higher resistance to pitting and crevice corrosion in acidic and salt-water environments, giving it the name “marine grade” stainless.
Grade 316 also contains a higher percentage of nickel than 304 stainless steel (10% vs. only 8%) which results in much improved corrosion resistance. This makes 316 stainless a better choice for use in chemical processing plants, oil refineries, and medical devices, as well as saltwater & marine applications, such as docks, catwalks, railings, and roofs.
316 Pros: Stronger than 304 stainless, more resistant to corrosion & pitting from saltwater and chemicals, good forming and welding characteristics.
316 Cons: More expensive and somewhat more difficult to weld and form than 304.
Industrial Metal Supply stocks a wide range of stainless steel forms, including bar, sheet & plate, tubing, pipe, angle, and perforated sheet. Drop by one of our six locations in Southern California and Arizona, or visit us online today!
