Aluminum Vs. Steel.
There is a lot of debate in the sign industry about what metal is best for sign manufacturing. Aluminum is the preferred metal for the majority but there is still a large group that prefers steel for sign fabrication.
Aluminum or Al atomic number 13 in the periodic table is a fairly soft metal only when compared to steel. Its atomic mass is 26.981539 u and has a melting point of 1,221°F.
A great aspect about aluminum is the valence electrons of the element can be +2 or +3. This means oxygen, which is +6 combines with aluminum creating aluminum oxide Al2O3. Aluminum oxide which is a compound is stronger and more durable than aluminum by itself. The longer aluminum is exposed to the air (Oxygen) the stronger it becomes. Even in weather, you can place aluminum outside in the rain and it will never become anything but Aluminum Oxide. Then it is technically an ageless material.
Most people would consider the fact that aluminum is such a light weight material a downside to this product. However, aluminum is still extremely strong material despite its low mass. Meaning if you use a thick grade aluminum to fabricate a sign you will have the durability of the sign you need and a very light weight sign. A light weight pole sign, blade sign, or even a wall sign is actually a positive aspect of this material. The less the sign weighs the less stress it puts on the integrity of the wall surface to which it is mounted. Most of the time the walls where the signs are mounted are merely stucco and wood. Engineers commonly call out simple leg bolts to hold the signs in place which can take a limited amount of weight. During a strong guest of wind, if the sign is large and heavy putting a lot of stress on the leg bolts or wall the sign is more likely to fall off then a sign that is lighter such as an aluminum structure.
Steel is mainly iron and carbon. It is often mixed with a few other elements depending on the manufacture but the elements they are combined with are negligible and we won’t address them here. Iron in its raw state is about twice as massive as aluminum. The atomic mass is 55.845 u and that directly correlates with the melting point which is about twice that of aluminum 2,800°F. Carbon which is the second element that makes up steel has an atomic mass that is 12.0107 u which is much less than aluminum. Carbon may be what makes life and diamonds possible but it should not be assumed that if it is part of a compound that it will not break down or will be a stronger compound in some way. The fact of the matter is once the iron is exposed to the elements it reacts with the oxygen and the carbon just becomes a byproduct. The equation for rust is (Iron = Fe, Oxygen = O) 4Fe + 3O2 = 2Fe2O3. Ferric Oxide (Fe2O3) also known as common rust is an extremely undesirable sign product in most cases. Eventually the rust will take over the entire steel structure, stain the surrounding area, and eventually the sign will just fall apart.
Antique signs with a certain amount of rust can sometimes be a desirable collector’s item so in some applications when restoring a sign or creating a sign you intend to look old steel is defiantly the material of choice.
Stainless steel contains about 12-30% chromium. Chromium binds with the oxygen much like Aluminum Oxide and can protect the steel from rusting. Often, the surface area of stainless can be scratched revealing a small area of exposed steel and that can rust but in properly configured stainless steel there would be enough chromium to prevent the steel underneath from further rusting. Stainless steel is about as massive, strong, and durable as steel or iron but since it contains Chromium the effects of rust are often negligible.
Standard steel is not an optimal product unless you’re restoring an antique sign or creating a sign you would like to have the antique look. Aluminum is lighter weight, becomes a stronger material when it oxidizes, but it dents much more easily if a thick material is not used. Stainless steel is extremely heavy, doesn’t’’ dent as easily, but is more costly and harder to use. In the end, the material used truly depends upon the application but in most cases sign manufacturing in Aluminum is a desirable use of the element.
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