Steel – Mild, Galvanised, Stainless or Weathering?

Steel is the material of choice for signage and wayfinding structures due to its exceptional durability and versatility. Its strength and resistance to corrosion make it ideal for withstanding the elements and ensuring longevity, even in harsh outdoor environments.

Choosing the right type of steel can be confusing, but making the right choice ensures your stainless steel signage board and other wayfinding structures stand the test of time. This article explores the different types of steel, their unique characteristics, and the best use scenarios for each, empowering you to make an informed decision.

We will delve into the properties of mild steel, galvanised steel, stainless steel, and weathering steel, examining their strengths, weaknesses, and suitability for various applications. By understanding the nuances of each steel type, you can select the optimal material that aligns with your project requirements, ensuring a visually appealing and long-lasting signage solution.

What is steel?

Steel is a versatile alloy primarily composed of iron and carbon. The manufacturing process begins by heating iron ore, coal, and limestone in a furnace to produce molten iron, known as pig iron. This pig iron is then combined with scrap steel and other elements like chromium, nickel, or manganese to create different types of steel with varying properties.

The four specifications for steel signage

There are four main specifications for steel used in signage and wayfinding structures. Choosing which one is right for your project depends on factors like the intended use, environmental conditions, and budget.

Mild steel

Mild steel is an alloy composed primarily of iron and carbon, with a carbon content ranging from 0.05% to 0.25%. This low carbon content makes mild steel relatively soft and ductile, contributing to its affordability and versatility. One of the key advantages of mild steel is its suitability for machining and welding processes. Its malleability allows it to be easily cut, shaped, and joined, making it an ideal choice for fabricating various signage and wayfinding structures.

However, it’s important to note that mild steel is susceptible to corrosion, especially in outdoor environments. To ensure longevity and protect against rust, mild steel signage requires surface coatings or protective treatments when used for exterior applications.

Mild steel works best for indoor signage or structures that will be shielded from direct exposure to the elements. It can also be used for outdoor applications when combined with protective coatings such as paint, galvanisation, or powder coating. Examples of suitable applications include indoor directional signs, interior wayfinding systems, and outdoor signage with proper protective finishes.

Galvanised steel

Galvanised steel is produced through a process called hot-dip galvanisation, where mild steel is immersed in a molten bath of zinc. This creates a protective coating that shields the underlying steel from corrosion. The zinc layer forms a tight metallurgical bond with the steel, providing superior corrosion resistance compared to bare mild steel.

One of the distinctive features of galvanised steel is its spangled or mottled appearance, which is attributed to the zinc coating. This finish enhances the visual appeal and contributes to the material’s durability. Galvanised steel offers excellent corrosion resistance, making it suitable for outdoor applications where exposure to moisture, rain, and other environmental factors is expected.

While galvanised steel is highly durable, it’s important to note that over time, the zinc coating can gradually degrade, leading to potential corrosion. However, this process is significantly slower than the corrosion rate of uncoated mild steel, extending the material’s lifespan and reducing maintenance requirements.

Galvanised steel is an ideal choice for outdoor signage and wayfinding structures in environments with moderate exposure to the elements, such as parks, urban areas, or coastal regions with moderate humidity and salt levels. Its corrosion resistance and durability make it a cost-effective solution for applications that require long-term performance without extensive maintenance.

Stainless steel (Grades 304 & 316)

Stainless steel is widely chosen for signage and wayfinding structures due to its exceptional corrosion resistance and sleek, modern appearance. Its durability makes it ideal for high-traffic areas, public spaces, and environments exposed to moisture, pollution, or coastal air. Two common grades used in signage applications are 304 and 316 stainless steel, each offering unique benefits based on their composition.

Grade 304 stainless steel contains 18% chromium and 8% nickel, providing excellent resistance to rust and staining. This makes it a reliable choice for urban settings, indoor signage, and outdoor installations in non-marine environments. Its combination of strength and aesthetic appeal ensures longevity while maintaining a polished, professional look.

Grade 316 stainless steel includes 16% chromium, 10% nickel, and 2% molybdenum, enhancing its resistance to corrosion, especially in marine and industrial environments. The added molybdenum helps protect against saltwater damage and harsh weather conditions, making 316 stainless steel the preferred choice for coastal areas or locations with high humidity.

Stainless steel is often seen in public spaces where durability and aesthetics are equally important. A prime example is the wayfinding system installed in Windsor, Berkshire, where millions of visitors navigate the historic town each year. Given the location’s significance and the sheer number of pedestrians, the signage needed to be highly durable and adaptable.

Stainless steel in Windsor, Berkshire

For this project, Made by Landmark provided Barcelona monoliths, a versatile wayfinding solution that allows customisation in size, finish, and graphics. These monoliths had to withstand constant exposure to the elements while maintaining their high-end appearance. Additionally, due to Windsor’s frequent public events, the structures required a removable foundation system—allowing them to be quickly taken down and replaced with a flush covering when needed.

The monolith panels, made from toughened glass, feature easily updatable graphics, ensuring that the wayfinding system remains relevant as the town evolves. This case highlights the practical advantages of stainless signage: resilience, adaptability, and minimal maintenance, all while complementing the heritage and prestige of a world-famous location.

Weathering steel (e.g., Cor-Ten)

Weathering steel, commonly known by the trademark Cor-Ten, is a unique material that develops a protective patina over time, making it a popular choice for signage and architectural structures. This patina formation process occurs as the steel is exposed to alternating wet and dry conditions, allowing a stable rust-like coating to form. Unlike conventional steel, which deteriorates with rust, weathering steel’s patina acts as a self-sealing layer, preventing further corrosion and eliminating the need for additional coatings or maintenance.

One of the key advantages of weathering steel signage is its long-term durability with minimal upkeep, making it ideal for natural landscapes and rugged environments. However, the material requires a consistent wet/dry cycle to develop its protective layer properly. If exposed to constant moisture without drying periods, the steel may continue corroding rather than stabilising. 

Additionally, early in its weathering process, the material can stain nearby surfaces as runoff carries iron oxide particles. This makes it important to consider placement and design strategies like using standoffs, drip edges, or drainage systems to prevent staining on porous materials like concrete or stone.

Weathering steel in action

A great example of weathering steel’s impact can be seen in the signage and wayfinding system at Hutchinson’s Bank, London. This ecologically rich area, managed by the London Wildlife Trust, is home to rare butterflies and orchids, offering visitors a peaceful retreat just a short distance from New Addington tram station. To complement the natural surroundings, Landmark supplied weathering steel monoliths at the site’s three main entrances. Over time, these structures have transformed from their original dull steel finish to a striking orange-red patina, standing out beautifully against the lush green backdrop.

Beyond the monoliths, the wayfinding project also included lamppost finger arms guiding visitors from the tram station and timber fingerposts marking trails throughout the site. The use of weathering steel here was a strategic choice—not just for its durability but for its ability to blend harmoniously with the environment while offering a bold, visually appealing contrast. A year after installation, a revisit confirmed the success of the material, with the monoliths ageing gracefully and continuing to enhance the site’s natural beauty.

Key considerations

When selecting the appropriate steel specification for signage, it’s crucial to consider several key factors:

Corrosion resistance: Different steel types offer varying levels of corrosion resistance. Mild steel is prone to rusting and requires protective coatings, while galvanised steel provides better resistance through its zinc coating.

Aesthetic preferences: The desired aesthetic plays a significant role in the decision. Mild steel can be painted in various colours, while galvanised steel has a distinctive silvery-grey appearance. Stainless steel offers a sleek, modern look, and weathering steel develops a striking orange-red patina over time, blending harmoniously with natural surroundings.

Budget constraints: Cost is often a deciding factor. Mild steel is generally the most economical option, followed by galvanised steel. Stainless steel and weathering steel tend to be more expensive but offer long-term durability and lower maintenance costs.

Environmental factors: The installation location’s environment should be considered. Marine environments may necessitate the use of corrosion-resistant materials like stainless steel or weathering steel. Urban areas with high pollution levels may also require more robust options.

Final thoughts

Choosing the appropriate steel type for signage and wayfinding structures is crucial to ensure durability, functionality, and an appealing finish. Considering factors like corrosion resistance, aesthetics, or budget, understanding the properties of mild steel, galvanised steel, stainless steel, and weathering steel enables informed decisions. By choosing the suitable material, councils and organisations can create steel signage solutions designed to withstand environmental conditions while maintaining their intended purpose and visual appeal.

For expert guidance on selecting the best steel for your signage project, reach out to Made by Landmark. Our team can provide tailored advice and high-quality solutions to match your specific needs. Get in touch today to explore the best options for your wayfinding and signage requirements.