Outdoor structures such as bridges, buildings, and home furniture face challenging conditions. Exposure to moisture, temperature fluctuations, and pollutants can cause corrosion and subsequent deterioration of the products.

To ensure longevity and structural integrity, the choice of metal is crucial. This article explores the best metals for outdoor use, focusing on their properties and applications.

Major Outdoor Structures and the Conditions They Face

Bridges are among the most critical structures, often exposed to harsh environmental conditions. Famous examples include the Golden Gate Bridge in San Francisco and the Brooklyn Bridge in New York.

These structures face constant exposure to moisture, especially in coastal areas, where salt can accelerate corrosion. Additionally, bridges endure significant mechanical stress from traffic loads and thermal expansion and contraction due to temperature changes.

Iconic buildings like the Empire State Building in New York and the Shard in London feature metal exteriors that enhance their aesthetic appeal and durability. These buildings must withstand various weather conditions, including rain, snow, wind, and UV exposure. Pollutants in urban environments can also contribute to the corrosion of metal surfaces, necessitating materials that offer robust resistance.

Outdoor furniture, commonly made from metals like aluminium and steel, must endure continuous exposure to the elements. Rain, sun exposure, and physical wear and tear are common challenges. Examples of outdoor furniture include patio sets, garden benches, and metal chairs. These pieces need to be lightweight yet durable, easy to maintain, and resistant to rust and corrosion to ensure longevity and usability.

Key Requirements for Outdoor Metals

Several critical factors must be considered to ensure the material’s performance and longevity in challenging environments when selecting metals for outdoor use. These key properties include:

Corrosion Resistance

Corrosion resistance is paramount for outdoor metals. Exposure to moisture and pollutants accelerates corrosion, leading to structural failure. Metals used outdoors must be corrosion-resistant metals so that they can resist rust and deterioration to maintain their appearance and functionality.

Durability and Strength

Durability and mechanical strength are essential for functional applications. Metals need to withstand physical stress, weathering, and potential impacts. The right metal choice ensures the structure remains robust and safe over time.

Maintenance and Longevity

Low maintenance is a key consideration for outdoor metals. Frequent repairs and upkeep can be costly and impractical. Choosing a metal that requires minimal maintenance extends the lifespan of the structure and reduces long-term costs.

Best Metals for Outdoor Use

When selecting rust proof metals for outdoor structures, here are some popular picks used worldwide:

Aluminium

Aluminium is a lightweight, durable, and corrosion resistant metal, it’s ideal for outdoor use. It is commonly used in outdoor furniture, window frames, and roofing. Aluminium’s natural oxide layer protects it from corrosion, ensuring low maintenance and long-lasting performance. Its aesthetic appeal and ease of fabrication add to its popularity for various outdoor applications.

An example of an outdoor structure made from aluminium (and stainless steel) is the canopy of the futuristic Louvre Abu Dhabi, which utilizes aluminium’s lightweight and corrosion-resistant properties for both aesthetic appeal and structural integrity.

Stainless Steel

Stainless steel is renowned for its high strength and excellent corrosion resistance. It is frequently used in bridges, sculptures, and outdoor fixtures. Stainless steel’s resistance to rust and staining, combined with its durability, makes it a preferred choice for outdoor structures requiring both strength and longevity. Its sleek appearance also makes it suitable for decorative elements.

The Gateway Arch in St. Louis, Missouri, is a prime example of an outdoor structure made from stainless steel (and concrete), showcasing its durability, strength, and resistance to corrosion.

Galvanised Steel

Galvanised steel, with its protective zinc coating, offers robust corrosion resistance at a cost-effective price. It is widely used in fencing, outdoor structures, and hardware. The galvanization process enhances the steel’s durability, protecting it from rust and extending its lifespan. Galvanised steel is an excellent choice for applications where cost and corrosion resistance are primary concerns.

Copper and Brass

Copper and brass are naturally corrosion-resistant and possess antimicrobial properties. They are commonly used in roofing, decorative elements, and electrical components. Over time, copper develops a patina that adds to its aesthetic appeal while providing additional protection against corrosion.

Brass, an alloy of copper and zinc, combines strength with an attractive appearance, making it suitable for various outdoor decorative applications.

The Statue of Liberty’s distinctive spire incorporates copper, which originally had a shiny reddish-brown color. Over time, it has developed a green patina, providing both aesthetic appeal and long-term protection against the elements.

Corten Steel

Corten steel, also known as weathering steel, forms a stable rust-like appearance after exposure to weather. This unique property makes it popular for building facades, sculptures, and bridges.

The rust layer acts as a protective barrier, reducing the need for maintenance. Corten steel’s high strength and distinctive appearance make it a favorite for architects and designers seeking both functionality and aesthetics.

The Angel of the North sculpture in Gateshead, England, made from Corten steel, illustrates the material’s unique rust-like appearance and high strength, making it a striking and durable landmark.

Conclusion

In summary, aluminium, stainless steel, galvanised steel, copper and brass, and Corten steel are among the best corrosion resistant metals for outdoor use. Each metal offers unique properties that make it suitable for specific applications, ensuring durability, corrosion resistance, and aesthetic appeal. Choosing the right metal for outdoor structures is crucial for maintaining their functionality and appearance over time.

Looking ahead, advancements in metal treatments and coatings promise to improve the performance of outdoor metals. Emerging technologies may offer even greater resistance to corrosion and weathering, further extending the lifespan of outdoor structures. As materials science continues to evolve, the options for durable and attractive rustproof metals will only expand, providing new possibilities for architects, builders, and designers.