What is the difference between aluminum and stainless steel

Mosi Li
Mosi Li

Director Project Engineer at 3Q Machining - China top CNC Machining Custom Part Manufacturer

What is the difference between aluminum and stainless steel

What is the difference between aluminum and stainless steel?

The stainless steel and aluminum is the most popular metal material for machining and the most widely use metal material for medical, industrial, electronic, computer, marine, aerospace applications

The general differences between stainless steel and aluminum are: 

Aluminum is much “cheaper,lighter, easier machining” than stainless steel, while stainless steel is generally much stronger than aluminum. The machinability of aluminum is much better that save machining timing and cost, and the aluminum 6061 can be heat treated to have high strength similar with stainless steel , but its overall lower strength, comes from the fact that it is a much softer metal for machining.

10 Differences Between Aluminum and Stainless Steel

Aluminum and Stainless Steel might look similar, but they are actually quite different. Keep these 10 differences in mind when deciding which type of metal to use in your next machined custom part project:

1. Strength to weight ratio.

The weight of Aluminum is almost only one third of stainless steel, that’s why aluminum is light weight metal material, and the most popular aluminum 6061 can be heat treated to get similar strength of stainless steel.

This is the main reason why aluminum is widely use for aircraft and  aerospace application.

2. Corrosion.

Stainless steel 304 and 316, it has good corrosion resistance without any surface treatment.

After do surface treatment such as electrolysis or spray, plating, stainless steel has excellent corrosion resistance.

Aluminum 1100, 5052, 6061 has good corrosion resistance, which is mainly attributed to its passivation layer.

When aluminum is oxidized, its surface will turn white and sometimes pits will appear.

But after Anodizing, the aluminum can have excellent corrosion resistance.

3. Thermal conductivity.

Aluminum has better thermal conductivity than stainless steel.

This is also one of the main reasons why it is used in car radiators and air-conditioning devices.

4. Material and Machining Cost.

Aluminum is generally cheaper than stainless steel, due to its raw material cost is only 1/2 or 1/3 of stainless steel, also aluminum its machining cost is only 1/3 of stainless steel.

5. Machinability.

Aluminum is relatively soft and easy to cut and shape, which means aluminum is good for cnc machining and other machining.

Due to its wear resistance, stainless steel is more difficulty to be machined by tools.

Compared with aluminum, stainless steel is more difficult to shape and machined.

6. Welding.

Stainless steel is relatively easy to weld, while some aluminum is difficult, for example, aluminum 7075 is poor welding, but aluminum 3003 has excellent welding.

7. Thermal performance.

Aluminum becomes very soft at temperatures above 400 degrees.

Stainless steel can be used at much higher temperatures than aluminum.

8. Conductivity.

Compared with most metals, stainless steel is a very poor conductor.

And aluminum is a good electrical conductor.

Due to its high conductivity, light weight and corrosion resistance, high-voltage overhead power lines are usually made of aluminum.

9. Strength.

Regardless of weight, stainless steel is stronger than aluminum.

But after heat treating, aluminum 7075 has high strength which is similar with stainless steel but lightweight, that’s why it is widely use for  aerospace application.

10. The impact on food contact safety.

The reaction of stainless steel 304 and 316 to food is none, hence SUS 304 and SUS 316 is completely food contact grade material and widely use for kitchenware, tableware, medical equipments.

Aluminum will react with food, thereby affecting the safety and taste of food, which is not food grade material.

In general, aluminum is easy to be machined by CNC, and is only 1/3 cost to be machined with similar strength and high corrosion resistance plus lightweight, that is why is aluminum is the most popular and good metal material for cnc machining, although steel is the widely and most use metal material in the world.

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