Stainless Steel Vs Aluminum - What Is The Difference

Today, aluminum and stainless steel are unavoidable. Getting about one's daily activities requires contacting aluminum or stainless steel. These two metals are used to make bridges, aircraft, buildings, kitchen appliances, and many others.

Despite having a similar appearance, stainless steel and aluminum exhibit various qualities that set them apart in manufacturing. Therefore, more than choosing the best project design is needed; the metal type also significantly impacts the project's success and durability. As a result, this article compares stainless steel with aluminum using around 17 different features.

STAINLESS STEEL VS ALUMINUM – THE DIFFERENCES

Stainless steel and aluminum display a wide range of remarkable qualities that can be utilized to distinguish them from one another. In this chapter, these characteristics will set stainless steel apart from aluminum. These properties include elemental composition, electrical resistance, thermal conductivity, melting temperature, hardness, and weight.

1. COMPOSITION OF ELEMENTS

When choosing a metal for a project, it is essential to consider its elemental composition. A metal's constituent parts give it qualities like hardness, corrosion resistance, melting temperature, and many more. In contrast, stainless steel comprises various components in various ratios. Chromium makes up 11% of stainless steel, whereas the other elements range in concentration from roughly 0.03% to over 1.0%. Other components include aluminum, silicon, sulfur, nickel, selenium, molybdenum, nitrogen, titanium, copper, and niobium.

As previously said, each elemental composition influences the metal's characteristics; for instance, the chromium content controls its heat and corrosion resistance. On the other hand, aluminum comprises various components, including silicon, zinc, magnesium, manganese, copper, iron, titanium, chromium, zirconium, and many more.

2. RESISTANCE TO CORROSION

Aluminum and stainless steel have extremely corrosion-resistant qualities. However, stainless steel has an advantage over aluminum because of its elemental makeup. Chromium, iron, nickel, and other elements are found in stainless steel. Chromium is a supplement that provides stainless steel with an invisible barrier to corrosion. This protective layer bears the weight of rusting stainless steel. The stainless steel's chromium shield simply regenerates itself when any rust on its surface is washed off.

Aluminum, on the other hand, corrodes instead of rusting, like stainless steel does. It's interesting to note that aluminum has a shield, a thin layer of aluminum oxide that shields the metal from rust. However, aluminum is still susceptible to other types of corrosion, even with aluminum oxide shielding.

3. ELECTRICAL CONDUCTIVITY

Metal electrical conductivity, which measures how strongly it conducts electric current, is one of its essential properties. Copper is used as a benchmark to assess the conductivity of stainless steel and aluminum to estimate their electrical conductivity. This is due to copper's conductivity rating of 100, which is very conductive.

Aluminum is a superior conductor to steel compared to copper electrical conductivity. With only 30% of copper's weight, it exhibits around 61 percent of conductivity. This makes it an ideal material for high-voltage overhead power lines and long-distance electrical transmission. Stainless steel is a poor electricity conductor compared to aluminum and copper. Only roughly 3.5% of copper's conductivity is present.

4. THERMAL CONDUCTIVITY

When choosing a material for your project, thermal conductivity is a crucial issue to consider. Metals' capacity to conduct or transport heat is called thermal conductivity. It would help to consider the material's thermal conductivity to choose a suitable material for various applications. A material with high thermal conductivity makes for an excellent radiator, whereas a material with low thermal conductivity makes for an excellent insulator.

In contrast, aluminum has a thermal conductivity of 1460 BTU-in/hr-ft2-°F (210 W/m-K), which is significantly higher. This is why radiators and air conditioners are its main applications. Unlike aluminum, which typically softens at temperatures exceeding 400 degrees Fahrenheit, stainless steel can be used at considerably heightened temperatures.

5. MELTING TEMPERATURE

When choosing materials, melting point is also crucial. This is because metals are most easily shaped in liquid. This implies that a material's formability can be estimated from its melting point. Another factor to consider is the possibility of component failure after a material exceeds its melting point or temperature. 

As a result, a material's melting point is the temperature at which it changes from a solid to a liquid state. Stainless steel, in contrast, has a melting point between 1230 °C to 1530 °C (2250 - 2790 °F). In contrast, aluminum has a lower melting point than stainless steel, at 660.37 °C (1220.7 °F). This demonstrates that stainless steel is better suited than aluminum for heat resistance applications.

6. HARDNESS

In terms of hardness, the metal's relative value specifies how it reacts to etching, deformation, denting, or scratching along its surface. An instrument known as an indenter machine is frequently used in the manufacturing sector to conduct this hardness test.

Material hardness plays a crucial role in strength. It can be assessed in various ways, but in this instance, we're using the Brinell scale to compare stainless steel hardness with aluminum. Because stainless steel has a higher Brinell hardness (80–600 HB) than aluminum (15 HB), it is harder to shape than aluminum. Stainless steel is preferred over aluminum in applications where hardness is required.

7. DENSITY

Generally speaking, stainless steel, which can be recycled without losing strength, is more robust than aluminum. It weighs roughly one-third as much as stainless steel. While stainless steel has a density of 8.0 g/cm3, aluminum has a density of only 2.7 g/cm3. These figures demonstrate that aluminum weighs less than stainless steel. Due to its lightweight, aluminum is mainly employed in skyscrapers and aircraft. Nowadays, aluminum is used to construct the vast majority of buildings around the globe. Aluminum alloys have also been developed to handle the weight of large glass panes necessary to erect tall buildings.

8. DURABILITY

When faced with everyday demands, a material is durable if it works without extensive repairs or maintenance. In their respective fields, stainless steel and aluminum are both resilient materials. However, choosing the most durable material is essential, especially if your project's requirements prioritize it.

Stainless steel is the clear winner when it comes to strength and hardness. This explains why most automobiles and trucks use more stainless steel than aluminum. Aluminum is less robust and long-lasting than stainless steel. Hence, it is used instead in automotive and other applications.

9. MACHINABILITY

The ease with which a material may be machined is called its machinability. Additionally, the material's cutting conditions and physical characteristics affect its machinability.

In this instance, aluminum is more machinable than most metals, including stainless steel. This is explained by the material's decreased hardness, which causes it to chip quickly during processing. Aluminum can be more easily shaped than stainless steel. The metal is more easily machined with easy chipping since the cutting tools put more time and effort into the workpiece than the chips they have just produced. Additionally, aluminum can be machined three or four times faster than stainless steel.

10. FORMABILITY

The ability of a material to demonstrate plastic deformation when formed without damage is known as formability. Compared to aluminum, which is relatively soft and more straightforward to form and cut, stainless steel is more rigid and more resistant to wear and abrasion. Compared to stainless steel, aluminum alloys, and tempers are more prone to dents, dings, and scratches. Despite being solid and robust, stainless steel is less prone to warp, distort, or bend when subjected to pressure, heat, or weight. Aluminum is a fantastic material choice for applications where formability is valued for a project.

11. WELDABILITY

The application determines whether to use aluminum or stainless steel for a project. Whether welding stainless steel or aluminum components, a quality joint is always necessary. Stainless steel and aluminum weld differently and have various quality variations that might be helpful in specific industrial applications. 

Compared to welding aluminum, stainless steel welding is more convenient and cost-effective. Aluminum welding demands increased proficiency and cleanliness, yet aluminum products are corrosion-resistant and lightweight. On the other hand, stainless steel is 2.5 times heavier and significantly more robust than aluminum. As a result, unlike aluminum, it does not easily split when welded but can flex and distort.

12. YIELD RESISTANCE

The highest stress at which a part or material permanently distorts is yield tensile strength. The yield point is the starting point of non-linear deformation. A portion of the deformation that occurs after a material reaches its yield point is permanent and irreversible. Low-strength aluminum has a yield strength of 7 MPa, while high-strength aluminum has a yield strength of 11 MPa.

High-strength stainless steel has a yield strength of over 2500 MPa, while low-strength stainless steel has a yield strength of only 25 MPa. Therefore, stainless steel is chosen if your project's need is related to its strength.

13. TENSILE POWER

On the stress-strain curve, the ultimate tensile strength is the highest. This stress is considered the most significant a material can withstand when in tension. Fracture will occur if stress is applied and maintained. This value, typically 50 to 60% broader than the yield stress for a few metals, is higher than the yield stress in most cases.

In this instance, we tested stainless steel and aluminum, and the results showed that stainless steel had more tensile strength than aluminum. While pure aluminum has a tensile strength of 90 MPa and can reach over 690 MPa for some heat-treatable aluminum alloys, stainless steel ranges from 34.5 to 3100 MPa.

14. SHEAR FORCE

A material's resistance to shear force before the component fails in shear is known as its shear strength. This tends to occur on a plane in a direction parallel to the force acting on it. Depending on the alloy, stainless steel's shear stress ranges from 74.5 to 597 MPa. In contrast, aluminum's shear strength ranges from 85 to 435 MPa. This shows that stainless steel is superior to aluminum in applications requiring excellent shear load resistance.

15. COLOR

Users should be aware of the color of the materials to be used to prevent choosing the incorrect material for their project. Aluminum and stainless steel are two metals with striking visual resemblance but differ.

Aluminum has a silvery-white look that ranges from silver to drab gray, depending on the material's surface. For smooth surfaces, aluminum typically has a silver appearance. In contrast to aluminum, stainless steel is bright and silverier. Even when the weather has altered these appearances, stainless steel will typically appear shiny and more dazzling than aluminum.

STAINLESS STEEL: APPLICATIONS

Stainless steel is now utilized in a wide range of industrial applications. 100% recyclable, stainless steel is ubiquitous and used every day. It can be applied in the kitchen, streets, hospitals, buildings, and many other places. Stainless steel has the following principal uses:

• Culinary (cookware, cutlery, and many more kitchen accessories).
• Architecture (bridges, airport roofs, statues, and monuments).
• Surgical instruments and medical equipment (such as hemostats, implants, and temporary crowns).
• Applications related to the automotive industry (auto body, rail cars, light commuter trains).
• Applications involving aerospace (planes and spaceships).
• Water (plumbing, wastewater treatment, desalination, and ben treatment).
• Conversion of biomass into paper, pulp, and paper (digester, bleach plant).
• Petroleum and chemical processing.
• Food and drink.
• Energy (power generating, electrolyzer).
• Jewelry.
• Ejector pins are made of stainless steel in a plastic mold.
• Firearms.
• 3D modeling.

ALUMINUM: APPLICATIONS

Since aluminum has high corrosion resistance, it is typically employed in many sectors. It is available in various alloys and shapes that significantly enhance aluminum's mechanical properties, especially when tempered. For instance, the most popular aluminum alloy is found in beverage cans and foils, which contain 92% to 99% aluminum. The primary uses of aluminum are as follows:

• Transportation (spacecraft, bicycles, trains, vehicles, trucks, ships, airplanes, and more).
• Packaging (frames, cans, foils).
• Building and construction (including sheathing, doors, windows, roofing, building wire, and many more items).
• Applications involving electricity (transformers, motors, generators, conductor alloys, and Others).
• Household products, including furniture and culinary items.
• Tools, pipelines, processing equipment, and other equipment and machinery.

STAINLESS STEEL VS ALUMINUM – COST

Compared to stainless steel, aluminum is more expensive. Aluminum, on the other hand, weighs around one-third of stainless steel. As a result, when stainless steel and aluminum are placed side-by-side in the same volume, stainless steel typically costs 30% more. This indicates that aluminum is the least expensive material and is preferred to stainless steel if the cost of the material is a significant consideration for all other factors.

CONCLUSION

Aluminum and stainless steel are the most widely used metals in the manufacturing industry. Their uses span various industries, including aircraft, medicine, food, architecture, construction, etc. Aluminum and stainless steel are similar, but they also possess distinctive qualities. However, choosing the ideal metal for your project involves more than just price; you must carefully consider the elements or properties discussed in this article. Your project will succeed if the guidelines are followed.