Corten vs Mild Steel Garden Edge – Do The Differences Matter?

Corten vs Mild Steel Garden Edge – Do The Differences Matter?

Garden edging serves a crucial function in landscaping. Creating clear boundaries between different areas and lending a finished, polished look to outdoor spaces. Whether you're separating a flower bed from a lawn, preventing soil erosion, or simply enhancing the aesthetic appeal of your garden, the material you choose for edging can make a significant impact. We are often asked, does it really matter if I use mild steel edging rather than Corten?  Both have their advantages, but do the differences between them really matter? In this blog, we’ll explore the key distinctions between Corten steel and mild steel, helping you make an informed decision based on your garden's needs.

What Is Corten Steel?

Corten steel, also known as weathering steel, is a group of steel alloys specifically designed to form a stable, rust-like appearance after exposure to the elements. It was originally developed for building railcars in the 1930s by the United States Steel Corporation and has since become popular in modern architecture and landscaping.

The key feature of Corten steel is its ability to form a protective layer of rust when exposed to air and moisture. This rust layer acts as a barrier, preventing further corrosion and giving Corten steel its unique, long-lasting finish. The steel’s rich, reddish-brown hue is highly valued for its rustic, industrial aesthetic. Corten fits seamlessly into both contemporary and natural settings.

What Is Mild Steel?

Mild steel, on the other hand, is a form of carbon steel with a relatively low carbon content, typically less than 0.25%. It’s widely used in construction, manufacturing, and everyday objects due to its affordability, malleability, and ease of welding. Unlike Corten steel, mild steel doesn’t form a protective rust layer, so when it oxidizes, it continues to rust until the steel degrades. To prevent this, mild steel must be treated with protective coatings like paint or galvanization, especially if it’s being used outdoors.

The Key Differences Between Corten and Mild Steel

1. Corrosion Resistance

The most significant difference between Corten and mild steel is how they handle corrosion. Corten steel is engineered to resist atmospheric corrosion by forming a stable rust layer on its surface. This patina acts as a shield that prevents deeper rusting, ensuring that the steel retains its structural integrity over time. Mild steel, however, lacks this self-protective ability. Without a protective coating, it will continue to corrode when exposed to moisture.  This corrosion will eventually weaken the material and compromise its appearance and functionality.

2. Appearance and Aesthetics

Corten steel is famous for its warm, earthy tones that develop as the steel weathers. This makes it an ideal choice for creating a rustic or industrial look in garden settings. The weathered finish blends well with plants, stone, and other natural materials. The rich patina also changes over time, giving your garden edge a dynamic, evolving appearance.

Mild steel and Corten are hard to tell apart before they weather and develop the rusty patina.   The striking visual differences become more apparent over time. Mild steel will take longer to develop the rusty patina and will be much more patchy where inconsistent weathering occurs. If used on a small groundline edge, the difference may not be so noticeable.

3. Durability and Longevity

Corten steel’s weathering properties give it a significant advantage in terms of durability, particularly in outdoor environments. Once the protective rust layer forms, it halts further corrosion, enabling us to offer a lifetime warranty on Corten steel edging. This makes it an excellent choice for garden edging, which is continually exposed to moisture, soil, and changing weather conditions.

Mild steel falls when it comes to longevity because it doesn’t self-seal; the steel will continue to rust. Often if mild steel is chosen, a thicker grade steel is used to increase the life span. When comparing mild steel and Corten, mild steel is a terrible performer but if compared against a timber sleeper, a mild steel edge performs fairly well.

4. Cost

One of the most practical considerations when choosing between Corten and mild steel is cost. Corten steel is more expensive than mild steel due to its unique composition and the additional processing required to create its weather-resistant properties. If you’re working within a tight budget, mild steel may be the more attractive option, especially for smaller garden projects.

However, it’s important to factor in the long-term costs associated with maintenance. While mild steel may have a lower upfront cost, you may need to replace it in 5-10 years time because it has rusted away.

5. Maintenance Requirements

One of Corten steel’s greatest strengths is its low maintenance requirements. Once the initial rust patina forms, it doesn’t require painting, sealing, or any other type of ongoing care. The natural aging process of the steel is part of its appeal, and the weathered look continues to develop without intervention.

Mild steel, on the other hand, demands more upkeep, particularly when used in outdoor environments. To prevent rusting, mild steel needs to be regularly inspected and maintained. This could involve repainting, applying rust inhibitors, or replacing rusted sections. For garden edging, this maintenance can become a hassle. Especially in areas where the steel comes into frequent contact with water, such as near sprinklers or in rainy climates.

6. Sustainability

From a sustainability standpoint, both Corten and mild steel are recyclable, which makes them eco-friendly choices in terms of lifecycle. However, Corten steel has a slight edge in this regard due to its longevity and low maintenance. The reduced need for chemical treatments and coatings, as well as its resistance to corrosion, means fewer resources are used over its lifetime. Mild steel, depending on the protective treatments applied, may have a higher environmental impact due to the need for paints or galvanization.

7. Safety

Safety is an important consideration. While Corten offers a stable smooth finish that will last a lifetime, Mild steel will rust and could present as a safety issue.  As the steel rusts through it will create a sharp and dangerous edge if not replaced.  Sharp rusty exposed edges can cause physical injury and could lead to Tetanus.  

Which One Should You Choose for Garden Edging?

The choice between Corten and mild steel for garden edging largely depends on your specific needs and preferences. If you value durability, low maintenance, and a striking, weathered aesthetic, Corten steel is likely the best choice. It’s particularly well-suited for gardens where you want a natural, rustic look and minimal upkeep.

However, if you’re on a tighter budget or prefer the flexibility of painting and customizing your garden edge, mild steel might be a better option. Keep in mind that while it may require more maintenance over time, protective coatings can extend its lifespan and help maintain its appearance.

Conclusion

The differences between Corten steel and mild steel garden edging do matter, especially when you consider factors like appearance, durability, cost, and maintenance. Corten steel offers exceptional weather resistance and a distinctive look, making it a great choice for long-term garden projects. Mild steel, while more affordable, requires ongoing maintenance to prevent corrosion. Ultimately, the right choice depends on your garden’s style, your budget, and how much effort you’re willing to invest in maintaining the edging over time. Either way, both materials have their place in landscaping, and the decision comes down to personal priorities and the unique needs of your outdoor space.