Skip to main content

Types of Stainless Steel – 304, 316 and 430

Oct 29th 2020

Check out our huge selection of stainless steel equipment for cleanrooms and labs.

316 stainless steel table for cleanroom

Stainless steel isn't a single alloy but rather a group of iron-based alloys containing a minimum of 10.5% chromium. Other elements are added and the chromium content is increased to improve corrosion resistance, heat-resistance, mechanical properties, and/or fabricating characteristics. 

There are more than 50 stainless-steel grades that are recognized by the American Iron and Steel Institute (AISI.) Three general classifications are used to identify stainless steel. 

Stainless Steel Classifications

Type 304 is the basic chromium-nickel austenitic stainless steel and has been found suitable for a wide range of applications. It is the most readily available in a variety of product forms. This grade is easy to form and fabricate with excellent resistance to corrosion. It is a nonmagnetic steel.

The stainless alloy resists most oxidizing acids and can withstand all ordinary rusting. However, it will tarnish. It is immune to sterilizing solutions, most of the organic chemicals and a wide variety of inorganic chemicals. Check out our Type 304 tables, cabinets, sinks and more!

stainless steel gowning bench for cleanroomsOther types of stainless steel are used for critical environments that require a higher level of resistance to corrosion than Type 304 can offer. 

Type 316 is also austenitic, non-magnetic, and thermally non-hardenable stainless steel like Type 304. The carbon content is held to 0.08% maximum, while the nickel content is increased slightly. What distinguishes Type 316 from Type 304 is the addition of molybdenum up to a maximum of 3%. Molybdenum increases the corrosion resistance of this chromium-nickel alloy, withstanding attack by many industrial chemicals and solvents, and inhibiting chloride pitting. Molybdenum is one of the most useful alloying additives to fight corrosion.

By virtue of the molybdenum addition, Type 316 can withstand corrosive attack by sodium and calcium brines, hypochlorite solutions, phosphoric acid; and sulfurous acids used in the paper pulp industry. Therefore, this alloy is specified for equipment in the medical industry, pharmaceutical manufacturing, and sterile area. Type 316 is also used extensively for surgical implants. Need Type 316? We have a wide selection of tables, sinks, and lifts in our store.

stainless steel cabinet for cleanrooms

Type 430 is a low-carbon, plain chromium ferritic stainless steel, often used for kitchen-grade tables and utensils, along with other applications with less anti-corrosion demand. However, the stainless steel has good corrosion resistance in mildly corrosive environments and good resistance to oxidation at elevated temperatures. The steel has limited weldability and should not be used in it's welded condition for dynamic or impact loaded structures. Being a ferritic material, 430 is liable to brittle fracture at sub-zero temperatures, and cannot be used in cryogenic applications. As the steel does not contain nickel or molybdenum, it is less expensive than any of the 300 series steel.

430 is a simple corrosion and heat resistant grade and can be used in mildly corrosive conditions or where scaling resistance is required at moderate temperatures. Typical applications include: Automotive trim, kitchen utensils, sinks, washing machine parts and industrial pipe and tube. Heat resisting applications up to 759oC. Visit our store for Type 430 tables and sinks.

Type 430 vs. Type 304:

 - 430 grade stainless steel is magnetic,
 - 304 is non-magnetic
 - 430 is somewhat difficult to form, 304 is easier to form and weld
 - 430 contains 17% chromium and 0.12% carbon, 304 contains 18% chromium and         0.08% carbon

Type 304 vs. Type 316:

 - Both type 304 and 316 are easily welded and formed
 - Both types are non magnetic
 - 304 is made up of 18% chromium, 316 contains 17% chromium
 - 304 contains no trace of molybdenum, 316 contains 2.1% molybdenum
 - Largest difference: molybdenum is added to Type 316 to increase corrosion and pitting resistance

Resistance to Corrosion

stainless steel shoe racks for cleanrooms

It is important to choose the correct stainless steel type or grade based on its resistance to corrosion. Since stainless steel is an alloy of iron, the metal can corrode, forming rust. 

Acid chloride can cause “Pitting Corrosion” when chloride reacts with chromium to form chromium chloride. When this occurs, the stainless steel loses its chromium, leaving only iron. As the chromium is dissolved, chlorides bore into the steel, creating a smooth wall pit. 

The probability of pitting increases with higher temperatures, higher chloride content, and lower pH. Under these conditions, a type 304 stainless steel bucket could pit through in less than 8 hours. 

The pitting corrosion resistance improves when molybdenum is added to the stainless steel.

Another type of corrosion is “Crevice Corrosion”. The passive film on stainless steel can break down in sharp corners or overlapping surfaces. Therefore, the crevice needs to be large enough for the corrosive solution to penetrate and small enough for the solution to remain stagnant.

Stainless steel equipment can be composed of all three types of stainless steel: 316, 304 and/or 430. It's vital to choose the correct grade of stainless steel to meet your unique environment and application.

Check out our complete selection of 316 stainless steel tables (including fully welded construction, in custom sizes).

About Cleanroom World:

Cleanroom World is a cleanroom specialist in Centennial Colorado