When it comes to selecting materials for industrial applications, especially for components like stainless steel bag filter housings, choosing the right grade of stainless steel is critical. Among the most commonly used grades are 304 and 316 stainless steel. While both offer excellent corrosion resistance and durability, there are important differences between the two that can influence performance, particularly in harsh environments.
If you’re looking to truly understand the differences, here is our in-depth comparison of 304 and 316 stainless steel, highlighting their properties, corrosion resistance, and performance in corrosive applications, specific to bag filter housings, but relevant as general knowledge. We’ll also discuss how these differences align with various international standards and help determine which material is best for your stainless steel bag filter housings.
What Sets 304 and 316 Stainless Steel Apart?
Both 304 and 316 stainless steel belong to the austenitic family of stainless steels. Austenitic stainless steels are known for their excellent corrosion resistance, high ductility, and good weldability. However, their chemical composition differs in key ways that impact their resistance to certain types of corrosion and environmental interactions.
304 Stainless Steel
• Chromium (Cr): ~18-20%
• Nickel (Ni): ~8-10%
• Carbon (C): ≤0.08%
• Manganese (Mn): ≤2%
• Molybdenum (Mo): Not present
304 stainless steel is the most commonly used type of stainless steel worldwide due to its balance of cost and performance. It offers excellent resistance to oxidation, common chemicals, and moisture, making it ideal for a wide range of applications, including the construction of our stainless steel bag filter housings.
316 Stainless Steel
• Chromium (Cr): ~16-18%
• Nickel (Ni): ~10-14%
• Carbon (C): ≤0.08%
• Manganese (Mn): ≤2%
• Molybdenum (Mo): 2-3%
316 stainless steel contains a higher percentage of nickel and a notable addition of molybdenum. These differences in composition make 316 stainless steel significantly more resistant to certain types of corrosion, particularly in environments involving exposure to chlorides (like seawater) or harsh chemicals.
Molybdenum is a silvery-white, hard metal that is highly resistant to heat and corrosion. Molybdenum is often used as an alloying element in various steels and superalloys due to its ability to improve material strength and resistance to corrosion, with it’s high melting point of 2,623°C (4,753°F), making it very durable even under the most extreme conditions. Molybdenum is a small but essential component that dramatically enhances the performance of 316 stainless steel.
General Corrosion Resistance
In many industrial environments, including applications involving water or non-aggressive chemicals, both 304 and 316 stainless steel will perform well. For standard stainless steel bag filter housings used in these environments, 304 stainless steel may provide sufficient corrosion resistance while remaining cost-effective.
Resistance to Chlorides and Pitting Corrosion
The primary reason to select 316 stainless steel over 304 in certain applications is its superior resistance to pitting and crevice corrosion, which are common in environments rich in chlorides or salts. Chlorides, such as those found in seawater or de-icing salts, can cause localized corrosion in 304 stainless steel, forming pits that compromise the integrity of the material.
The addition of molybdenum in 316 stainless steel helps prevent this type of corrosion by forming a more stable passive layer on the surface, which resists breakdown in chloride-rich environments. For stainless steel bag filter housings exposed to seawater, salty air, or chemicals containing chlorides, 316 stainless steel is the superior choice due to its increased durability.
Acid and Chemical Resistance
316 stainless steel also offers improved resistance to acids, alkalis, and other corrosive chemicals compared to 304. This makes 316 stainless steel the preferred option for stainless steel bag filter housings used in chemical processing plants or in environments where the filter housing may come into contact with acidic or alkaline substances.
International Standards Defining 304 and 316 Stainless Steel
Various international standards organizations define the chemical composition and mechanical properties of stainless steel grades. These standards ensure consistency in manufacturing and allow industries to select materials that meet their specific requirements. Two key standards for stainless steel include:
• ASTM (American Society for Testing and Materials): The ASTM standard A240 specifies the chemical composition, mechanical properties, and other characteristics of 304 and 316 stainless steel used in plate, sheet, and strip forms, which are common in the construction of stainless steel bag filter housings.
• EN (European Norm): The European standard EN 10088-2 provides similar specifications for stainless steels, ensuring compliance with European regulations. 304 is commonly known as 1.4301 in this system, and 316 is referred to as 1.4401 or 1.4436, depending on the exact molybdenum content.
Meeting these standards guarantees that both 304 and 316 stainless steel meet strict requirements for use in a wide range of industrial applications, including filtration systems, food processing, and chemical handling.
Cost Differences and Long-Term Performance
One of the reasons 304 stainless steel is more widely used than 316 is due to its lower cost. Since 304 does not contain molybdenum, it is less expensive to produce than 316 stainless steel. For applications where exposure to harsh chemicals or chlorides is limited, 304 stainless steel is a highly cost-effective solution for stainless steel bag filter housings.
However, in environments where corrosion is a greater concern, the higher upfront cost of 316 stainless steel is justified by its longer lifespan and reduced maintenance needs. Over time, the superior corrosion resistance of 316 stainless steel can lead to fewer replacements, repairs, and downtime, resulting in lower total cost of ownership.
Mechanical Properties and Strength
While both 304 and 316 stainless steel offer similar mechanical properties, there are slight differences worth noting. Both materials exhibit excellent tensile strength, but 316 stainless steel is slightly stronger due to the presence of molybdenum. This added strength can be beneficial in applications where mechanical stress or heavy loads are factors.
For most stainless steel bag filter housing applications, 304 stainless steel will offer sufficient strength and durability. However, in more demanding environments where mechanical stress is combined with corrosive exposure, 316 stainless steel’s superior strength and resistance to stress-corrosion cracking make it the better choice.
Applications for 304 and 316 Stainless Steel Bag Filter Housings
When determining whether 304 or 316 stainless steel is the right material for bag filter housings, it’s important to consider the specific environmental factors the housings will be exposed to.
• 304 Stainless Steel: Ideal for indoor applications or outdoor environments with minimal exposure to corrosive agents. This grade is also widely used in food processing, brewing, and pharmaceutical industries, where chemicals and chlorides are not present in significant concentrations.
• 316 Stainless Steel: The better option for environments with higher exposure to corrosive agents, including saltwater, industrial chemicals, or acidic compounds. Industries such as marine, oil and gas, and chemical processing will benefit most from 316 stainless steel’s enhanced resistance to localized corrosion and harsh chemicals.
Choosing the Right Stainless Steel for Your Bag Filter Housing
When selecting materials for stainless steel bag filter housings, both 304 and 316 stainless steel offer excellent options, especially when compared to carbon steel. For general applications, 304 provides strong corrosion resistance at a lower cost, making it an ideal choice for standard industrial uses. However, in environments with exposure to chlorides, harsh chemicals, or acidic substances, 316 stainless steel’s superior corrosion resistance and strength make it the better long-term investment.
Understanding the differences between these two stainless steel grades helps ensure that your filtration systems are built to last, even in the most challenging environments. By choosing the right material for your bag filter housings, you can improve performance, reduce maintenance, and extend the life of your equipment. If you are still not sure what your process will subject your bag filter housings to, give us a call for a same day quote from one of our experts that can help to guide your decision.