page contents

Stainless Steel vs Aluminum

This question is often asked of us. Both of these materials have many similarities and are often confused. They each have their strengths as well as their best uses.

Can you tell the difference? Which image is aluminum and which is stainless steel? The answer is at the bottom of the page.

How are Stainless and Aluminum similar?

1.     Both of these materials are alloys.

What is an alloy? An alloy is a metal made by combining two or more metallic elements, especially to give greater strength or resistance to corrosion.

An aluminum alloy is an alloy in which aluminum (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. They also have two classifications, those being casting alloys and wrought alloys which are then divided into heat treatable and non-heat treatable.

 

A stainless steel alloy is also known as inox steel or inox from the French word inoxydable (inoxidizable) and has a minimum of 10.5% Chromium by mass. Molybdenum can also be added to increase corrosion resistance from chloride solutions.

 

2.     Both come in different grades which defines the typical use they will have.

 

The two most common aluminum grades are 6061 and 5052. 6061 grade is comprised of aluminum, magnesium, and silicon, and is used for more mechanical functions. 5052 grade aluminum is composed of aluminum, magnesium, and chromium and is typically used for appliances or vehicles.

 

The most commonly used grades of stainless steel are 316 and 18-8. 316 grade stainless contains chromium, nickel, and molybdenum, and is used when clean environments are necessary (i.e. healthcare and food service industries). 316 stainless steel is considered marine grade stainless and is least likely to rust even in highly corrosive environments.   

 

18-8 grade, also known as 304 is comprised of only chromium and nickel. 18-8 is used for cutlery, screws, machine parts, and headers on cars. 18-8 stainless is more likely to corrode than 316 stainless.

 

3.     Neither material will rust, however they both can oxidize over time.

 

Aluminum won’t rust because it doesn’t contain any iron or steel. The oxidation of aluminum creates a thin white layer of aluminum oxide that serves to prevent further corrosion of the metal and doesn’t flake like rust would.

Oxidized Aluminum

Oxodized Aluminum.jpg

Stainless steel won’t rust as long as the oxide layer remains intact. An environment high in chlorine however can corrode the material, as can a low oxygen environment.

 

4.     These alloys can be cut, shaped, and welded into various patterns.

 

Using a laser you can cut both aluminum and stainless steel, however stainless is a little more difficult to do so. Both metals are light reflective and heat conductive however so cutting them with a laser is more difficult than cutting carbon steel would be. New advances in laser cutting technology have eliminated much of the difficulty in cutting these materials.

 

Although both metals may be welded, welding aluminum however can be a tricky process. If the aluminum oxidizes during the weld it will form an oxide on top which has a much higher melting point than the base aluminum. This can result in the base melting without you seeing a change in the top layer at all. Stainless is more likely to discolor when it is welded and if you are attempting to achieve a mirror polish finish, this can be extremely time consuming.

 Left- Aluminum Welding Right- Cutting Stainless Steel

How are Stainless and Aluminum different?

                                                             

5.     The biggest difference is of course the price of both materials.

 

Both of these materials are priced based on how much they weigh with it coming down to price per pound. Stainless steel costs about 32% more per pound than aluminum does.

 

Aluminum

12” by 12” by 1” = $60.26 (14lbs) = $4.28 per lb.

 

Stainless

12” by 12” by 1” = $232 (41lbs) = $5.65 per lb. (32% more)

 

However, the difference per square inch or square foot is even more staggering.

 

The cost for stainless steel is going to be about 4 times more than aluminum when comparing a similar size shape.

 

6.     What are the weight differences?

 

Stainless Steel weighs about three times as much as aluminum does. Therefore if you use stainless for your project, you are going to have significantly higher weight, and significantly higher cost.

 

7.     The finishes of both materials differ depending on the use.

 

There are different styles of finishes such as a mirror polish for stainless steel. This gives it a highly reflective surface by sanding the surface finely and using a buffer. This process much more difficult with aluminum as doesn’t have the hardness that steel does and will lose the polish rather quickly.

 Left- Aluminum Finishes Right- Mirror Polished Stainless Steel

8.     How resistant are these materials to corrosion?

 

Due to the oxide layers of both materials they are highly resistant to corrosion due to the chromium within the stainless steel. They are not however immune to it. An environment high in chlorides will eventually break down the oxide layer and begin to corrode the metal underneath. The same will happen in oxygen low environments.

 

Aluminum can form an oxide layer on top to prevent corrosion of the metal and will also break down in an acidic environment. It differs however in that it can also be affected by basic solutions that are low on the pH scale.

 Left- Corroded Aluminum Right- Corroded Stainless Steel

9.     Which industries use which metal?

 

Aluminum is typically used in any industry where something metal is used such as such as bicycle frames, flashlights, weapon suppressors, and food/drink cans, as well as aircraft, fuel lines/tanks, streetlights, rivets, and marine applications.

 

Stainless steel is the choice for when cleanliness is a priority such as food service or medical fields due to the fact that it won’t rust, such as in food processing, pharmaceutical equipment, wastewater treatment, and marine applications, and also being used for cutlery, screws, machine parts, and headers on cars.

 Left- Food Processing Equipment Right- Car Frame Manufacturing

 

10.             How hard are these metals?

 

The hardness of both materials is also quite different. Aluminum is soft as far as metals go and is not ideal for use in construction as it has more flexibility and can be bent much easier. Stainless steel has much more rigidity and is much more difficult to bend, but at the same time this makes it more difficult to shape.

 

Which material do you believe works best for your needs?

 

            For us aluminum is the choice and we use it for almost everything. We choose it for its strength, its high corrosion resistance, as well as the most important aspect, its weight. Due to the weight of aluminum it can be hung on any wall with the use of drywall anchors, and when necessary a french cleat.

 

(The aluminum is the first image and the stainless steel is the second image. They look very similar don’t they? Congrats to you if you guessed this one right!)

follow me on instagram