A Brief History
In the 1870s, sheet metals appeared in the United States being used for shingle roofing, stamped ornamental ceilings, and exterior facades. Today, aluminum and galvanized sheet metal are quite popular. Each of them has its pros and cons. To determine which of the presented materials is better, it is necessary to consider their characteristics in detail.
Galvanized sheet metal
The price of galvanized products is lower; however, the complexity of processing such elements and the difficulty in mounting them level this advantage. Zinc-coated steel is protected from aggressive external influences, but be aware that the surface layer is also subject to corrosion, only to a lesser extent. To increase the resistance to corrosive phenomena, the material is painted. Many buckets are made of galvanized steel – its appearance resembles white mud or rust. For these buckets, you can remember that once the galvanized steel is mechanically damaged, the rusting of the metal under it begins. Therefore, galvanized sheet metal is unstable to physical effects due to the high risk of damage to a thin galvanized layer. For instance, when carrying out installation works, the galvanized facade profile is cut to size right on the object. Usually, rust appears at the cut point.
The higher cost of aluminum products is compensated for by the simplicity and convenience of their installation, as well as greater safety and durability during operation. The material has a relatively low weight and high resistance to corrosion. Under the influence of oxygen, the aluminum surface is covered with a stable, dense oxide film. Aluminum oxide forms a chemically inert protective layer that protects the metal from destruction.
Another advantage of using aluminum steel is that systems made from this metal can be used in extremely corrosive environments. For example, for arranging swimming pools exposed to the aggressive effects of chlorine, or for erecting open structures that are within 50 meters from the sea or ocean. In similar conditions, the galvanized profile has a much shorter service life and quickly loses its properties.
Designs of any configurations are created from aluminum profiles – zenith lanterns, curtain walls, entrance groups, vestibules, partitions, domes, etc. The material is notable for its lightness with simultaneous strength. Similar systems made of galvanized steel will require reinforcement of the bearing parts of the building, preparation of support structures, additional protective treatment.
Aluminum is only unstable to contact corrosion, often with cathode metals. For example, if aluminum grids contact with copper, they are the first to collapse in the shortest possible time at the points of contact. Similarly, aluminum gratings are unstable to cadmium steel – it should be avoided. Aluminum sheets are not suitable when working with indium, gallium, amalgam and mercury – under their action, aluminum quickly collapses. Also aluminum doesn’t stand the contact with sea water – the constant presence in it will gradually destroy the aluminum lattice.
If we compare galvanized and aluminium steel for facade construction, steel with zinc plating and aluminum alloy sheets are the closest competitors. But, nevertheless, steel sheet has advantages:
- at the same thickness, steel is 2.5-3.0 times stronger;
- galvanized steel has better corrosion resistance;
- steel has higher strength at high temperatures which is important in case of fire, and aluminum dramatically reduces strength at T>200 ° C;
- The upper limit of the operating temperature of aluminum is 85 ° C. The temperature of thermal deformation – from 115 to 165 ° C for different aluminum alloys. For steel – above 300 ° С.
- Corrosion resistance of galvanized steel with zinc coating thickness of 275 g/sq. m is not less than 30 years, the service life – more than 50 years. Aluminum alloy: durability up to 25 years, service life up to 30 years.
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For more information, please see…
Richards, Joseph William. Aluminum: Its History, Occurrence, Properties, Metallurgy and Application, Including Its Alloys. Franklin Classics, 2018.
The featured image in this article, a photograph of a sign showing the lower portion of the sign with side cladding and chaser troughs made of galvanized sheet metal in place at the Chicago Theater, 175 North State Street, Chicago, Cook County, IL, comes from the Historic American Buildings Survey (HABS), Historic American Engineering Record (HAER) or Historic American Landscapes Survey (HALS). This image or media file contains material based on a work of a National Park Service employee, created as part of that person’s official duties. As a work of the U.S. federal government, such work is in the public domain in the United States. See the NPS website and NPS copyright policy for more information.