Protective coatings are fundamental to steel corrosion prevention. There are two types of coatings that provide a barrier between valuable metal and the elements: galvanized metal and aluminum-zinc alloy.
Galvanized
Offering some protection against corrosion-causing elements, galvanized metal is a sheet of steel that has been coated with a thin layer of zinc oxide (99.8% zinc). Initially, galvanized metal maintains its appearance; however, once exposed to the elements, the zinc coating begins to corrode at the cut edge, eventually spreading across the entire surface, quickly deteriorating the original façade while weakening the steel. In fact, galvanized metal may begin to break down within 10 to 15 years of element exposure.
Aluminum-Zinc
In 1972, Bethlehem Steel developed GALVALUME® sheet steel consisting of 55% aluminum, 43.5% zinc and 1.5% silicon. It is applied via a continuous hot dip process over the base metal. The generic process of applying an aluminum-zinc alloy in a hot dip delivers superior oxidation-resistance, granting two to four times the life span of traditional galvanized metal. It offers the corrosion resistance and heat reflectivity of aluminum coatings, along with the formability and galvanic protection of cut edges of zinc coatings.
Silicon enhances the adhesion of the coating, keeping it in place when the steel is rolled, stamped or bent, while the aluminum additive and zinc fusion create microscopic particle areas within the coating. The aluminum-rich areas, which corrode very slowly, provide long-term durability, while the zinc-rich areas, which corrode preferentially, provide galvanic protection.
The Differences
There is a visible difference between the two as an aluminum-zinc alloy metal appears to almost have a matte finish.
Galvanized metal corrodes linearly, and eventually, the zinc coating is completely depleted, whereas an aluminum-zinc alloy experiences some corrosion, but on a smaller and less significant scale.
An aluminum-zinc alloy metal is less prone to rusting than normal galvanized steel, and less likely to completely break down, even after a few decades.
The Advantages
An aluminum-zinc alloy offers many advantages when compared to galvanized metal.
Aluminum-zinc acts as a sturdy, defensive barrier that resists rust, the elements and fire. It provides exceptional heat and corrosion resistance, typically four to six times greater than galvanized metal. And, unlike galvanized finishes, aluminum-zinc alloy features a resin coating that not only protects against corrosion and fingerprints, but also presents a better surface for paint application, making it ideal for both interior and exterior finishes.
KPS Global®: Dedicated to Exceeding Expectations Through Innovation
KPS Global® has a long history of designing, manufacturing and installing custom, insulated panel systems. As industry experts, KPSG not only recognizes the customer’s need to protect their product, equipment or work, but is dedicated to providing durable solutions that offer sustainable investment performance as well.
As such, in May of 2019, KPS Global transitioned to an aluminum-zinc finish, adding robust protective capabilities to enhance the longevity and appearance of their innovative solutions. To learn more, contact KPS Global today.
1 GALVALUME is a registered trademark of BIEC International, Inc.
