What is the difference between 304 and 316 stainless steel? It’s a common query of many people.
Stainless steel alloys contain a mixture of elements including chromium, nickel, carbon, and manganese. SS 304 and SS 316 are the two widely used grades of 300 series of stainless steel. Both of them are used in a variety of applications for their durability, appearance, and resistance to corrosion.
But what distinguishes one grade over another?
The following four facts will explain the differences between 304 and 316 and help you to learn which one is the best.
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304 and 316 Stainless Steel – 4 Interesting Facts
The following 4 facts will help you learn the difference between 304 and 316 stainless steel.
Fact 1: There’s no visible difference between grade 304 and 316
304 stainless steel– also called 18/8.
(It describes its composition of 18% chromium and 8% nickel)
316 stainless steel – also called marine grade stainless steel
Both the 304 and 316 are grains or polished the same way. So, you can’t identify them just with the naked eye.
Both the grades are austenitic, non-magnetic, and non-hardenable through heat treatment. They are capable of resisting corrosion and quite durable.
Type- 304 corrodes slowly and it eventually shows the signs of wear and tear. This grade of stainless steel is vulnerable to corrosion from chloride/ salty solutions and marine environments where grade 316 stainless steel comes in picture.
Fact 2: There are differences in the chemical composition of 304 and 316
So, where is the difference between these two grades?
The difference is in their structure and cost as well.
The addition of Molybdenum to grade 316 makes the major difference. This alloy makes a subtle but significant difference. Molybdenum increases the toughness, hardenability, hardness, strength as well as the corrosion resistance of SS 316, making it perfect for more acidic environments.
Overall, the SS316 is more resistant to oxidation and corrosive environments than 304 due to the addition of Molybdenum.
Chemical composition of 304 and 316
All types of steels have the same carbon and iron composition. So, what’s the specialty of stainless steel?
Well, stainless steel contains chromium that gives this alloy corrosion resistance. Grade 304 and 316 are the two most ordinarily utilized grades.
Chemical Composition Chart of 304 and 316
Chemical composition of 304 (% by weight)
Chemical composition of 316 (% by weight)
This composition chart shows that there are some critical differences in components and percentage of chromium and nickel.
In 304, chromium 18% while in 316 it’s 16%.
304 contain 8 % nickel, while it’s 10% in 316.
The more significant difference is- there is no Molybdenum in 304 whereas grade 316 contains 2% molybdenum. This added element turns the common 300 series stainless steel into a superpower with the ability to withstand harsh (like seawater and de-icing salts) environments.
The benefits of adding Molybdenum to 316 are:
- It boosts general corrosion resistance
- It offers increased strength at elevated temperatures
- It enhances pitting resistance from chloride ion solutions
Fact 3: Both the Grade stainless steels are the perfect choices for multitude of projects.
Both the SS 304 and 316 offer many advantages for professionals. However, 304 is the most widely-used austenitic stainless steels. Due to its malleability, grade 304 is more versatile than grade 316.
Some common applications of 304 involve:
- Kitchen equipment including kitchen sinks, pots and pans and flatware
- Dishwasher and refrigerators
- Corrosion-resistant electrical enclosures
- Stainless hardware
- Auto trim and molding
- Pressure vessels and Piping
- Liquid storage and tanks and food prep equipment
- Hose clamp
- Building facades
- Heat exchangers
- Exhaust manifolds
- Commercial food processing equipment
- Structures in environments that would corrode standard carbon steel
- Other applications involving freshwater environments
Grade 316 holds up well in severe conditions. For this reason, this type is perfect for many industrial and chemical applications.
Some common applications of 316 involve:
- Marine application, especially those with chlorides present
- Refinery equipment
- Fasteners, pulp and paper processing equipment
- Pharmaceutical processing equipment
- Medical devices/ surgical instrumentation
- Chemical processing and storage equipment
Fact 4: 316 stainless steel is more expensive than 304
304 vs. 316 stainless steel cost comparison – which is more costly?
Stainless steel is one of the least costly material options in the metal industries. But the upfront cost of 316 is a little higher than 304. 316 stainless steel costs 20 to 30 percent more than 304.
Considering the cost of replacing an entire process line plus manufacturing downtime, these costs are insignificant. The resistance to rust and corrosion of 316 steel will save a lot on the backend.
When choosing between stainless steel alloys remember to factor in what you’re processing.
Which Grade Is Perfect: 304 or 316?
Let us help you choose the right one!
There are three factors that you need to consider when choosing the right type of stainless steel for a particular job. These are:
- Tensile strength
- Corrosion resistance
- Heat exposure
Simply to say, between 304 and 316- which one you should use- depends on your application types.
Additionally, cost is also an important factor to consider when choosing between 304 and 316.
Grade 304 may be the right choice In the following circumstances:
If your application requires excellent formability, grade 304 stainless steel will be a better choice. The reason is- the presence of Molybdenum may adversely effect on the formability of stainless steel.
When cost is a concern, opt for grade 304 as this grade stainless steel is less expensive than grade 316.
Grade 316 may be the right choice In the following circumstances:
- If there is a high amount of corrosive elements in the environment, or near chlorides, salty seawater, or de-icing salts
- If the instrument be exposed to water consistently or will be placed underwater
- If the applications require higher hardness and strength, then grade 316 is the best option to use
In conclusion, both 304 and 316 are suitable for strength, corrosion & heat resistance, and welding. However, situations involving acidic materials or highly concentrated saline environments may cause corrosion and consequent failure of grade 304 stainless steel.
The SS316 gets the slight edge in all these categories. Due to the variation in alloying elements, 316 is better corrosion and pitting resistance to chlorides than 304.
Thanks for reading our article on difference between 304 and 316 stainless steel.