Metal signs speak volumes. Their sturdiness, malleability, and sleek finish add a level of finesse to business signs. Making the best decisions about the design of your business’ sign shouldn’t be your sole consideration. The type of metal used also plays a major role in how long it will last in external weather conditions. Aluminum and stainless steel are two of the best metals to use in metal signs. The table below compares both types of metals so that you can make an informed decision about the best metal to use for your sign.
Aluminum vs Stainless Steel
weight
Aluminum is about 1/3rd the weight of stainless steel (and steel for that matter). Aluminum is much much lighter! A 4ft by 4ft sign in our multiple layer format could weigh 40lbs. This is without a doubt light enough to hang directly on drywall with standard wall anchors. If the same sign were made out of all stainless steel, the weight would be 120lbs and would require reinforcement behind the drywall.
Strength
The strength of metals can be measured in a few different ways and they are all related to how different loads can be applied to an item. Two of the most common ways are tensile strength and shear strength.
Tensile strength - Tensile strength is the amount of load or stress that can be handled by a material before it stretches and breaks. Think about having a hole in the material and then hanging weight from it. This is often represented with PSI. Your standard alloy of aluminum would be rated at 40,000 PSI. Stainless Steel would be 70,000 PSI.
Shear strength - Shear strength is its ability to resist forces that cause the material's internal structure to slide against itself. Think about having a bolt fixed in a horizontal position, and a weight hanging from that bolt immediately after the fixed position. At a certain weight, the bolt is going to fail and the weight is going to move. For aluminum this is 30,000 PSI and stainless it is around 50,000 PSI.
What does this mean for signage? Well, aluminum is plenty strong to be used for signage, particularly if it is layered. If the sign was a single layer and strength was a major concern, then stainless steel could be the better option.
Strength to weight ratio
(Force per unit area divided by density)
Aluminum has a tensile strength of 276 MPa and a density of 2.81gcm-3. Therefore it’s strength to weight ratio is ~99.
Stainless steel has a tensile strength of 505 MPa and a density of 8 gcm-3. Therefore it’s strength to weight ratio is ~63.
From a strength to weight perspective, aluminum is stronger than stainless steel. That is to say for the increase in weight from aluminum to stainless steel, you get less than a corresponding increase in strength.
Corrosion
Aluminum creates a passivation layer that helps it resist oxidation and corrosion. Aluminum comes in multiple different alloys with the bulk of all aluminum being 5052 and 6061. 5052 is considered marine grade and is more resistant to corrosion than 6061. Most of your “extrusions” are made of 6061. If aluminum is left outside it will begin to get a milky oxidation on the face of it quickly. If it is powder coated, the aluminum is protected from the atmosphere and won’t corrode which will leave the powder coat in tack for decades. Brushed aluminum on the interior of a building will retain its shiny look.
Stainless steel contains chromium which has corrosion resistance properties. Stainless also comes in different alloys, with the bulk of all stainless being 304 and 316. 304 is the most common type of stainless steel. 316 has a greater resistance to corrosion. 316 costs costs more than 304, but it will last longer and rust less.
Typically if you are making something out of stainless it is because you want the look of shiny metal and therefore you don’t typically powder coat stainless steel unless you are extremely concerned over corrosion, then 316 stainless steel powder coated is going to be your absolute best bet.
Cost
Aluminum is more expensive than stainless steel, when you compare it by weight. However, aluminum is about 1/3rd the weight of stainless steel, and when you compare the cost of the same volume of material, stainless steel is much more expensive, usually by about 30%
Malleability
5052 aluminum is very malleable. 6061 is likely to crack if bent. Aluminum has a lower tensile and shear strength than stainless steel and therefore is more likely to bend.
Stainless steel is more likely to keep it’s shape than aluminum,
Electrical Conductivity
Aluminum conducts electricity well. You can often find large scale electrical wires made of aluminum as aluminum is much cheaper than copper and the conductivity is similar (but less).
Stainless Steel is one of the poorest conductors of electricity amongst all the metals.
Welding
Aluminum is more difficult to weld than stainless steel, but with the advent of welding machines that can MIG weld aluminum, welding aluminum has become much easier. However, since the material is “soft” (when compared to stainless steel) you must be very careful when welding thin aluminum to not burn through it. When choosing an aluminum to weld, choose 5052, it is easier to weld than 6061. Use 100% argon shielding gas when welding aluminum.
Stainless steel is less difficult to weld than aluminum and you can also use a 100% argon shielding gas. However many welders will also use a mixed gas of 75% argon and 25% carbon dioxide.
How can we help you? Click the button below to get started on a free quote and we will help you however we can!
What does this mean for you?
Aluminum is a better metal to use for outdoor signs because it has better weather resistance than stainless steel. Stainless steel, however, has superior strength. Both metals can be used for indoor signs.
Essentially, the choice you make depends on what you’re willing to live with. Both metals will give you the refined look you desire. Their strength and weather resistance are the ultimate decision factors.
Our recommendation is always for aluminum since the weight is so much lower it make handling much easier!
