Introduction
Stainless steel is resistant to corrosion, strong, and durable. There are several grades of stainless steel. 304 stainless steel and 316 stainless steel are two of the most popular ones. They are both austenitic stainless steel with many similarities. However, they also have many differences when it comes to their application, chemical composition, corrosion resistance, and cost. This article will detail these differences to help you choose the grade of stainless steel most suitable for you.
Differences between 304 and 316 Stainless Steel
1. Chemical Composition
304 and 316 Stainless Steel differ in their chemical compositions significantly. Although they both have primarily iron, chromium, and nickel, their quantities and additional elements vary. The table below highlights the chemical composition of each:
| 304 Stainless Steel | 316 Stainless Steel |
| 16-18% Chromium | 18-20% Chromium |
| 8-10.5% Nickel | 10-14% Nickel |
| 0.08% Carbon | 0.08% Carbon |
| 2% Manganese | 2% Manganese |
| 1% Silicon | 1% Silicon |
| 0.045% Phosphorus | 0.03% Sulfur |
| 0.03% Sulfur | 2-3% Molybdenum |
304 stainless steel is also called 18/8 stainless steel as it has 18% chromium and 8% nickel content. The nickel makes it tough and ductile while chromium makes it resistant to corrosion.
In contrast, the 316 stainless steel has 2-3% molybdenum which makes it more resistant to corrosion, especially against industrial solvents and chlorides. This is the major difference in the composition of both grades of stainless steel.
2. Corrosion Resistance
304 Stainless Steel has great corrosion resistance, especially against most oxidizing acids. It offers excellent resistance to staining and rusting due to which it is a preferred choice in food processing and kitchen industries. However, it is prone to rust in high chloride environments, leading to localized corrosion in the form of pitting (small holes in the metal).
In contrast, 316 stainless steel is much more resistant to corrosive agents and chloride due to its molybdenum content. This makes it the right choice for chemical industries and marine environments. It also has excellent resistance against pitting and crevice corrosion which takes place in small spaces where corrosive agents or moisture can gather. This high-quality corrosion resistance makes 316 stainless steel the best choice for tougher conditions.
3. Mechanical Properties
304 and 316 stainless steels both have great mechanical properties, differing in some aspects.
314 and 316 stainless steels both resemble in their tensile strength of around 515 megapascals. Their hardness levels are also similar with a Brinell hardness of around 201 for 304 and somewhat higher for 316. Both are durable and strong. However, 316 stainless steel works well under tougher conditions due to its excellent corrosion resistance.
When it comes to ductility, both 304 and 316 stainless steels are extremely ductile. This refers to their ability to be bent into shapes or drawn into wires without breaking. Both are also easy to form and weld which makes them versatile for several applications.
However, molybdenum in 316 stainless steel reduces its ductility to some extent as compared to 304 stainless steel.
In terms of temperature resistance, both 304 and 316 stainless steel can bear high temperatures. However, 316 stainless steel has enhanced resistance to heat as it contains molybdenum and higher nickel. This is why 316 stainless steel is better for applications where exposure to higher temperatures may be expected.
4. Applications
304 Stainless Steel is used in the food and beverage industry in food processing machinery, storage tanks, and kitchen equipment. It is also a preferred choice for household use for items such as cookware, cutlery, and sinks.
Architectural applications of 304 stainless steel include cladding and railing formation. It is also used in the automotive and aerospace industries.
In contrast, 316 stainless steel is used in marine applications, such as propeller shafts and boat fittings where there is high exposure to seawater. In the chemical processing industry, it is used in pipes, tanks, and heat exchangers in chemical plants. In the medical field, it is used in surgical instruments and implants. It is also used in the pharmaceutical industry.
5. Cost
The difference in the cost of 304 and 316 stainless steel is quite significant. 304 stainless steel is more affordable than 316 which is why it is the choice for many where improved corrosion resistance of 316 is not required. Its cost-effectiveness and quality performance make it a preferred choice.
In contrast, 316 stainless steel is more on the expensive side as it has molybdenum and improved corrosion resistance. Therefore, it is used in harsh environments with exposure to chlorides and chemicals where 304 stainless steel would not work. Its high cost justifies its longevity and improved performance.
Conclusion
304 and 316 stainless steel are both strong, durable, and resistant to corrosion. The choice between the two depends on one’s specific requirements. In harsh environments, the more expensive 316 stainless steel would be better. But for general-purpose applications, the affordable and readily available 304 stainless steel would be a suitable option.
Understanding and knowing the differences between 304 and 316 stainless steel can help you make an informed decision regarding the grade of stainless steel most suited for your required applications. This will help you spend money efficiently and ensure you invest in the right grade of stainless steel.