Any layman with limited industry knowledge may fail to distinguish between a particular stainless steel grade and another. But for manufacturers and industry experts, the distinguishing features of different stainless steel alloys are evident. The two most popular stainless steel grades - grade 304 and 316 alloys - can bring this confusion.
At a glance, the two may seem identical. However, each has unique features that distinguish it from the other, and these could really impact your product's lifespan depending on how you intend to use the material.
All stainless steel alloys comprise different levels of chromium and iron mixes. The mixing ratios and other additional components are what determine the various features of each grade.
Grade 304 Versus 316 Stainless Steel
The 304 versus 316 is a timeless comparison that can be attributed to their striking similarities. Both alloys are part of the austenitic stainless steel family, one of the five groups of stainless steel. These include austenitic, martensitic, and ferritic stainless steel, as well as the PH Grades and Duplex Grades of stainless steel. These steel categories offer unique features used to meet different physical and environmental demands.
Grade 304 and 316 are comparable in chemical composition, attributes, and appearance. Both alternatives are famous for their durability and offer excellent rust and corrosion resistance.
The primary distinguishing feature between the two alloys is that stainless 316 contains molybdenum. This chemical element is useful for hardening and strengthening of steel. The alloy also contains more nickel than 304 but less chromium.
Among the two, 304 is the most popular and versatile austenitic stainless steel. The primary reason for this is its exceptional corrosion resistance. You'll also pay fewer dollars for the material than 316 stainless steel, another factor that contributes to its widespread use.
Grade 316 Stainless Steel
This is a popular grade of stainless steel alloy with a melting range of 2,500 – 2,550 °F or 1,371 – 1,399 °C. Considering it falls under the austenitic stainless steel alloy category, it possesses qualities like corrosion resistance, high nickel and chromium concentration, and lots of strength. The alloy's tensile strength stands at 579 MPa or 84 KSI (kilopound per square inch). Its maximum use temperature is about 800˚C or 1,472˚F.
As already stated, the alloy's formulation contains additional molybdenum. This is what contributes to grade 316's resistance to chloride pitting, alkalis, and acids.
Properties and Applications
This stainless steel grade comes in a close second to its grade 304 counterpart with regard to commonality. It portrays the same mechanical and physical properties, and it's almost impossible to identify without specialized equipment or tests.
The primary differentiator of 316 stainless steel is the material composition. It comprises:
- 16% chromium
- 10% nickel
- 2% molybdenum
Compared to 304, this alloy is more expensive per ounce of material. This is due to the inclusion of molybdenum and additional nickel content. However, you'll find it a superior alternative thanks to the increased resistance to corrosion resistance–particularly against chlorinated solutions and chlorides.
The above features make Alloy 316 an appropriate material in environments with powerful corrosives or where there's exposure to salt. Here are the typical applications of 316 stainless steel alloy:
- Marine parts
- Stainless steel baskets
- Medical/surgical equipment
- Chemical equipment
- Pharmaceutical equipment
- Outdoor electrical enclosures
Grade 304 Stainless Steel
This is another widely-used austenitic stainless steel alloy, and it is famous thanks to its durability, tensile strength, and resistance to oxidation and corrosion. The melting point of 304 stainless steel is higher than its 316 stainless steel counterpart, ranging between 2,550 – 2,650 °F or 1399 – 1454 °C. But as the material draws closer to these temperatures, it continues to lose its tensile strength gradually.
The stainless steel alloy material stands out with its incredible tensile strength of approximately 621 MPa or 90 KSI. Grade 304 also has a higher operating temperature of up to 870 °C.
Properties and Application
This member of the stainless steel family is the most popular. It has excellent resistance to corrosion thanks to the higher chromium percentage. The partial chemical makeup of grade 304 stainless steel below highlights the difference in chemistry between itself and 316 stainless steel:
- 18% chromium
- 8% nickel
Apart from the two major components, this stainless steel grade may also contain limited amounts of manganese and carbon. These components make it oxidation-resistant, hence the ideal material for sanitization and cleaning.
Other typical applications of this steel alloy include:
- Wheel covers
- Storage tanks
- Auto moldings and trim
- Kitchen appliances and equipment
- Electric enclosures
The numerous benefits of grade 304 stainless steel alloy make it a widely used material, but it has its unique setbacks. For instance, the material is highly susceptible to pitting and corrosion based on its current location. Exposure to saline environments and chloride solutions is not recommended. Only 25 ppm of chlorides is enough to catalyze pitting corrosion.
Is Grade 316 Stainless Worth the Extra Cost?
If your application contains chlorides or relies on potent corrosives, it is definitely worth it if you pay the extra dollars for grade 316 stainless steel materials. In such environments, this alternative will be more durable than the grade 304 alternative. This means many more years of useful life.
But if you have an application that uses milder acids or environments with zero concerns of salt exposure, then alloy 304 will work just fine, and at a lower cost.
When choosing between the two almost similar alloy materials, one must ensure they account for every environmental factor and process. For instance, if you're in the coastal region, you must avoid any material that's unable to beat chloride corrosion.
Overall, grade 316 will give you value if you seek the ultimate corrosion resistance.
Get Excellent Material from Global Leaders
Both the 316 and 304 stainless steel alloys are exceptional alternatives. They offer their unique strengths, which depend on end-use and the physical and mechanical properties you need.
Ulbrich Stainless Steels & Special Metals, Inc. is the industry leader in precision metals. We offer a wide variety of stainless steel solutions and products across multiple sectors. Our 304 and 316 alloy products are of excellent quality, and our solutions can turn your simple ideas into a reality.
Still stuck and wondering which stainless steel grade to choose for your project? You are not alone. Both alloy grades are excellent, and you may likely not know which one is the most appropriate. Contact us today and speak to a knowledgeable specialist who will guide you make the right choice.