Selecting Appropriate Cleanroom Stainless Steel: 304 vs 316 vs 304L vs 316L

Terra Universal manufactures a vast selection of stainless steel products for cleanrooms, hospitals, laboratories, and other controlled environments. Among these steel-constructed products, you'll find tables, workstations, glove boxes, pass-throughs, doors, and more.

There are several varieties of steel used to manufacture these products including 304, 304L, 316, and 316L stainless steel. So, let's unpack the differences between various stainless steel grades, finishes, and use cases.

304 vs 316 Stainless Steel Carbon and Chromium Content

Compared to 304 stainless steel, 316 stainless steel contains molybdenum, which improves corrosion resistance, especially in salt or chloride-laden environments.

By definition, stainless steels are steel alloys with a minimum chromium content of 10.5 wt% and a maximum carbon content of 1.2 wt%. The minimum chromium content of austenitic stainless steel is 16%.

316 steel is typically more expensive, due to its increased nickel content, and the presence of molybdenum. Meanwhile,

In comparison to 316L steel, 304 steel is stronger, harder, and more ductile. Thus, 304 is typically the most common choice for the construction and fabrication of structures, equipment, hardware, tooling, workstations, furniture, and end-use products.

Another factor that differentiates 304 and 316 steel is that 316 stainless steel contains more chromium than 304. Increasing chromium (Cr) content improves corrosion resistance but sacrifices some aspects of performance in hardness and tensile strength.

316L vs 304L Stainless Steel Performance

304L stainless steel is ideal when certain chemicals are present in the environment, such as sulfuric acid and phosphoric acid. While 316L stainless steel does have some resistance to these chemicals at low concentrations, 304L is less likely to deteriorate and offers better environmental resistance when certain acids are present.

316L stainless steel is best suited for improved corrosion resistance in marine and aquatic applications, especially when salt and ice are present. For pharmaceutical and laboratory environments where aggressive acids are present, 304L stainless steel is a preferable alternative.

316L-grade stainless steel contains more nickel and molybdenum than 304-grade, thus enhancing its corrosion resistance in wet environments and reducing degradation caused by harsh biocides such as bleach-based disinfectants or sterilants.

Steel Composition by Type: 304 vs 304L vs 316 vs 316L

• 304: 18% chromium, 8% nickel, max 0.08% carbon
• 304L: 18% chromium (20% max), max 0.03% carbon
• 316: 16% chromium, 10% nickel, 2% molybdenum, max 0.08% carbon
• 316L: 16% chromium, 10% nickel, 2% molybdenum, max 0.03% carbon

304 vs 304L Stainless Steel Performance

304 stainless steel is one of the world's most commonly used metals, and it's found in virtually every commercial, retail, or manufacturing environment. Besides being strong, durable, and aesthetically engaging, 304 steel accommodates most uses that require durability, and reliable tensile strength, and offers a broad range of resistance against chemicals, moisture, and high temperatures.

304L stainless steel is an alloy made up of a low-carbon version of 304 stainless steel. Lower carbon content reduces the likeliness that the carbide precipitates during welding, which can lead to

304L stainless steel is a low-carbon version of 304 stainless steel, which makes it less susceptible to carbide precipitation during welding. Carbide precipitation occurs when chrome and carbon content within the metal is drawn out from the material, which can lead to rust and oxidation. 304L steel is an excellent choice for use in corrosion-resistant structures where post-weld heat treatment is not necessary.

When Should I Choose 316 Stainless Steel Instead of 304 Steel?

In scientific and cleanroom environments, chemical characteristics and cleanliness are critical performance factors. Importantly, one must also consider the composition of integrated features such as hardware, latches, handles, and assembly components.

There are several instances where 316 steel offers greater resistance to environmental factors. Generally, 316 steel is specified for environments where 304 stainless steel lacks adequate corrosion resistance:

• Marine and aquatic applications,
• Salt and ice are present in the environment
• Environments with strict cleanliness requirements
• Equipment is exposed to harsh chemical cleaners

When Should I Select 316L Steel vs 316?

Generally, 316 steel is specified for environments with strict cleanliness requirements, or when equipment is exposed to harsh chemical cleaners and corrosive environments that 304 stainless steel cannot withstand. In food and beverage industries, 316L offers increased protection against salt, proteins, and strong acids or bases. 316L possesses enhanced resistance to chlorides and chlorinated solutions that are common in controlled environments and cleanrooms, such as Spor-Klenz® and Isopropyl Acetate.

Why Does Chlorine Cause Stainless Steel to Corrode?

The corrosion susceptibility of austenitic stainless steels increases with chloride concentrations. Here's how it works:

• In the corrosion pit or crevice, the surrounding electrolyte gains positive electrical charges.
• A positively charged pit attracts negative ions of chlorine.
• Chloride ions from the ambient environment accumulate on the surface and cause the corrosion rate to increase.
• The chloride ions attack the passive films on the surface of stainless steel and react with the metal matrix to cause the growth of stress corrosion cracking.

Corrosion cracking is an important issue for stainless steel installations that will frequently be subjected to chlorinated chemicals, saltwater, or combinations of salt and ice typical with winter conditions.

Stainless Steel Alternatives for Cleanrooms

White powder-coated steel provides a clean and attractive aesthetic. The glossy finish gives a spotless and well-maintained appearance. It also helps spot dirty surfaces more easily.

Terra’s signature white powder coat finish provides a high-quality, durable barrier to protect against corrosion, plus a clean and attractive aesthetic. The advanced heat-fused formulation exceeds ASTM and ISO paint standards to resist chipping, scratching, fading, and wearing.

Electropolished Stainless Steel

Electropolished stainless steel equipment is typically used in applications where a high degree of cleanliness and precision is required, such as in the medical, pharmaceutical, and food and beverage industries. It is also commonly used in the production of surgical devices and other medical equipment.

Electropolishing improves the corrosion resistance and durability of the stainless steel, making it more resistant to wear and tear over time.

As a result, electropolishing also increases corrosion resistance and improves the ease of cleaning via a smooth, reflective surface with a mirror-like finish.

Need Help Selecting the Right Steel for Your Application?

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