The primary function of the finish on steel roofs is to shield the roof from water, but the finish must also protect against harmful elements in the environment. Today’s steel coatings are very attractive. Steel building manufacturers and buyers want a dependable finish that will not lose its luster or peel or crack for many decades. Darker coatings, such as red and blue, are more sensitive to the sun’s rays and so, especially in southern climates, a tarnish protection must be applied.

Aluminum and zinc are often chosen to protect steel roofing due to their anti-erosive features. Zinc covering is designed to “melt”� at a calculated rate while safeguarding the underlying steel. The thicker the coating of zinc, the longer the roof protection will last. Generally, re-application of the coating is necessary about every five years. Galvanizing provides an additional protective barrier against the weather.

The popularity of aluminum-zinc finish is due to the robust nature of zinc plus the barrier aspects of aluminum. One common compound is Galvalume, introduced by Bethlehem Steel Corporation more than thirty five years ago. It consists of 43.5% zinc, 1.5% silicon, and 55% aluminum. Available as a lock-forming, structural, or commercial variety, Galvalume is a favorite structural roof protection layer.

Galfan is comprised of 95% zinc and 5% aluminum while the aluminum and zinc are usually bonded to the steel by means of a continuous hot-dip coating technique. This application is ideal for field flexing combined with configuration of panels since it traditionally will not flake or crack.

Alternatively, aluminum covering is usually installed as a material guard boundary. It is a by-product of aluminum oxide. Aluminum-zinc coatings afford great protection for many years, and they have become more popular than galvanized roofing. These new coatings can protect steel roofs for up to 30 years before any major maintenance is necessary. These finishes are less reactive than galvanizing, so they can sustain their guard barrier traits for much longer periods of time.   

Galvalume transparent coated panels have replaced oil, which made the rooftop sheets waxy and difficult to maintain. These adhesive panels are designed to dissolve gradually over about 1- 1½ years without chipping or crumbling. Because the transparent panels reduce the staining and marring that can happen with installation and storage of the roof segments, the requirement for lubricating substances is removed.

Finally, be aware that rust decay of roofing is more likely to occur at field-cut corners. The use of plant milled and finished steel roofing is strongly recommended. Zinc and aluminum coatings should not be in direct contact with unprotected steel to avoid galvanic processes. Also, because contact with timber decking can also harm zinc-aluminum coatings, always install a separating layer between the two materials. With the proper installation and materials, your building’s roof should last for decades.