304 VS 316 Stainless Steel
There are over 60 different grades of stainless steel, each with unique properties. The 300 series of stainless contains the two grades most often used in the electrical and mechanical industries: 304 SS and 316 SS. Grades in the 300 series have the addition of nickel and are able to maintain their austenitic microstrucre at low temperatures. This structural charateristic allows the steelto retain its tensile strength, corrosion resistance, toughness, and aesthetic features in virtually any working enviroment.
Aesthetically, there is no difference between Type 304 and Type 316 SS; in fact, the only way to differentiate between the two is to test them chemically. Their differing chemical makeup, however, has an effect on how they perform in certain environments. Requirements for one grade of stainless over the other are often dependent on the application or environment; therefore, it is important to understand the differences between the two.
Type 304 Stainless Steel
Type 304 SS is the most widely used grade of stainless steel and is considered the standard “18/8” stainless. Offering mechanical strength, corrosion, and oxidation resistance at a more economical price point, 304 SS is used in a wide range of components to provide basic resistance to corrosion.
TYPE 316 STAINLESS STEEL
The second most common grade, 316 SS is more corrosion resistant than 304 SS. Type 316 SS has a higher nickel content and benefits from the addition of molybdenum (2-3%) as an alloying element. The addition of molybdenum enhances the metal’s resistance to crevice corrosion and pitting from chloride solutions. The overall combination of increased nickel, molybdenum and other minor alloying tweaks improve the resistance of 316 SS to stress corrosion cracking, creeping, chemicals, solvents, sulfuric acids, and extreme temperatures. This makes 316 SS an ideal choice for electrical products subjected to industrial processing chemicals, ocean spray, or high-chloride environments. These chemistry changes result in an increase in the cost of 316 SS as compared to 304 SS.
304 vs 316 Stainless Steel Applications
Selection of a stainless steel alloy for a job is dependent on optimizing cost vs. performance based on the service environment and application. Below are a few examples of preferential alloys based on general service environments in the given industry.
Food & Beverage Processing Facilities – dairy and vegetable processing environments are generally milder and 304 SS is often sufficient; breweries and facilities processing meats, sauces, pickle liquors, etc. are often better served by the use of 316 SS;
Pharmaceutical Industry – generally 316 SS is the best choice in these uses;
Oil & Gas – 304 SS may be sufficient for use in oil and gas drilling and processing, but if the facility is located in a coastal or marine environment, 316 SS is recommended;
Pulp & Paper Mills – 316 SS is recommended for these severe environments;
Water & Sewage Treatment –316 SS is commonly used in these environments;
Marine & Coastal Applications – 316 SS would be preferred for use in or near salt water;
Heavy Industrial & Chemical Processing – 304 or 316 SS could be used depending on the chemicals present in the environment; please contact the factory for assistance specifying an alloy, if necessary.
At Gibson Stainless & Specialty Inc., we offer stainless steel rigid (heavywall) conduit and complementary stainless steel fittings. Our products are stocked in the higher grade of Type 316 SS and, in some products, Type 304 SS as well. For additional questions regarding grades of stainless steel or the use of Type 304 SS versus Type 316 SS in a specific application, please contact us today.