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Why are stainless steel and aluminum alloys used on exposed building exteriors?

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Stainless steel and aluminum alloys are frequently used on exposed building exteriors primarily because they form stable, protective oxide films when exposed to air. This natural barrier isolates the underlying metal from environmental elements, effectively preventing further corrosion.1

Stainless Steel

Stainless steel is a family of alloys that typically contains 10 to 30 percent chromium, which imparts remarkable resistance to corrosion and heat. While there are many grades, standard ferritic steels are commonly utilized in architectural applications, such as building trim, due to their durability and anticorrosion properties.2

Aluminum Alloys

Aluminum alloys are valued for their combination of strength, formability, and corrosion resistance. Specific alloys, such as those in the 3XXX series, are widely used for residential siding and industrial roofing. Additionally, 6XXX series extrusions are frequently employed for architectural elements like window frames and storm doors. To further enhance corrosion resistance and facilitate surface coloring, aluminum can undergo anodizing, a process that increases the thickness of the protective oxide layer.31