Last Updated on May 17, 2022
There are many practical applications to 316 and 308 grades of stainless steel. However, there are certain discrepancies that make both options differ from each other and more appropriate for specific purposes.
This article will explore the differences between 308 and 316 stainless steel. It can be helpful to anyone struggling to choose the right stainless steel. Later in the article, we’ll explain why choosing the appropriate stainless steel for the project at hand is important.
308 Stainless Steel
308 stainless steel is often utilized as a filler material when the project involves welding 304 stainless steel. This type of stainless steel has 20% chromium and 11% nickel. Hence, it can be considered an “austenitic grade” within the stainless-steel category.
We can also find other elements within the composition of 308 stainless steel, with iron being the highest in content at 66%. Other elements include Manganese, Silicon, Carbon, Phosphorus, and Sulfur.
316 Stainless Steel
316 stainless steel is an alloy that has molybdenum within its structure. It is characterized due to its high resistance against corrosion from different acids, like chloride. Therefore, it can be the right choice for certain applications, such as marine environments or other areas where the risk of exposure to chloride is relatively high.
It’s also worth noting that most of the composition of 316 stainless steel is iron. However, it also contains about 17% chromium and 12.5% nickel and other metals in smaller amounts, including molybdenum and silicon. Carbon and manganese can also be found within the structure of the 316-grade stainless steel.
Differences between 308 and 316 stainless steel
As we’ve mentioned, both stainless steel grades are better for certain applications. However, there are other differences that are important to note, even if they are relatively subtle.
Applications
316 Stainless steel
Firstly, 316 steel is quite common in the marine industry because the structures are constantly in contact with humidity. However, it is also present in other industries, such as the food and beverage industry or perhaps a few chemical processing methods.
Besides the marine industry, other applications may include commercial kitchens and appliances or perhaps pharmaceutical manufacturing.
308 Stainless steel
On the other hand, 308 steel is more appropriate for restaurant equipment and distillery paraphernalia. Other applications may include chemical tanks or perhaps during the fabrication of welding wire. As explained, it is also a common filler material when welding 304 stainless steel.
Properties
Another way to differentiate between 308 and 316 stainless steel is to take a look at the structure. 316 stainless steel only contains about 17% chromium and 12.5% nickel. On the other hand, we can find 20% chromium and 11% nickel within the structure of 308 stainless metal.
Additionally, 316 stainless steel possesses molybdenum, which means it is highly resistant to corrosion. On the other hand, 308 stainless steel is categorized as the second most used stainless steel type as it is utilized when welding 304 stainless steel, which happens to be the most common steel.
What to consider when choosing a stainless steel grade
While we’ve described the main differences between 308 and 316 stainless steel, here we have a few other tips you can take into account if you’re having trouble deciding what the best stainless steel grade is at the moment.
- When it comes to corrosion resistance, grade 316 is the best option you can choose due to the presence of molybdenum within its structure.
- Both grades 316 and 308 are categorized as austenitic stainless steel due to the small percentage of nickel found within their structure. However, austenitic stainless steels tend to be more expensive than ferritic steel.
- If you have a certain strength requirement for the steel you need to use, using grade 316 can be a great idea. It has excellent endurance and ductility compared to other steels, regardless if they are ferritic or martensitic.
- Grade 308 is often utilized for welding grade 304. Hence, we can say that its applications are not as extensive as those found in grade 316.
- Grade 316 is better for chemical applications.
- Both 308 and 316 are austenitic. Therefore, the iron remains as “austenite” or gamma iron while the steel is cool. In this phase, iron is non-magnetic.
Ferritic steel vs. Austenitic steel
Both terms are co-related and have importance in the topic at hand. The main difference between ferritic steels and austenitic steels like grades 308 and 316 is that austenitic stainless steel tends to have better protection against corrosion. Plus, austenitic stainless steels tend to have a “crystalline” structure, while ferritic steels have more chromium within their chemical structure.
So, which one is better? 308 or 316?
While both are more appropriate options in specific applications, it goes without saying that grade 316 has a better endurance to many chemicals than grade 308. Therefore, if the steel is destined for marine applications or other areas where the structure is going to be in constant contact with moisture, chloride, salt, or similar solutions, it’s better to use grade 316.
This article has explained the differences between grade 308 and grade 316 stainless steel. Both of these steels are better for certain applications, but the latter has more resistance than the other and can be a better option for certain structures, depending on the environment where they will be placed.
However, grade 308 is perhaps the best option when it comes to welding 304 stainless steel. Hence, it’s not correct to consider it useless.