What Is The Difference Between Corten And Mild Steel?

Whether it's a residential or commercial area, using the right materials is crucial when creating the perfect outdoor space. Steel is an excellent choice for use throughout your property, offering great strength, longevity and aesthetics. However, when choosing between Corten steel and mild steel, which is the best material for you?

 

Garden bollard light

 

What is weathering steel?
Corten steel, also known as weathering steel, is a high-strength, low-alloy steel that was originally developed to eliminate the need for painting. This material is widely used to create outdoor sculptures, including the Angel of the North, and large-scale infrastructures such as bridges, due to its amazing properties and great benefits.The name COR-TEN refers to two of the steel's remarkable properties: corrosion resistance and tensile strength.
Today, this steel is widely used in the construction and landscaping industries because of the beautiful finish it produces when exposed to the natural environment.

 

Garden Corten Steel Rusty Metal Outdoor Lighting

 

What is mild steel?
Mild steel is the most commonly and widely used mild steel on the market and is usually used for projects that require a lot of use, such as structural projects. This material is strong, flexible and cost effective, making it a very economical solution.

 

So what's the difference between the two?
Both Mild Steel and Corten Steel offer tons of benefits to the user, but there are some key differences between the two:

 

Corten Steel Lights

 

Appearance
At first glance, both Corten steel and mild steel have a dark blue surface and look very similar. However, when they are exposed to the elements, the weathering process begins and their appearance changes. Corten steel develops a beautiful orange patina early on, then gradually darkens to an orange-brown color, giving it a distinctive rustic look. Mild steel, on the other hand, takes on a darker orange-brown color from the start.

Corten steel typically develops its stable, protective patina within about 6-9 months to a year, depending on climate conditions. Mild steel can develop a visually similar rust-colored surface in a comparable timeframe, but unlike Corten, this is not a stable protective layer - mild steel continues to corrode underneath, gradually losing material thickness over time. The two can look very similar to the untrained eye in the short term, which is exactly why the composition difference below matters so much for long-term performance.

 

Corrosion
Although both mild steel and Corten steel do look similar after the complete weathering process, they do have very different corrosion results.

Over time, Corten will develop its unique layer of rust on the surface, which effectively acts as a protective barrier that prevents the steel itself from corroding, this means that Corten has an extremely long life span, degrading at a significantly slower pace compared to mild steel.

Mild steel does not have that same effect, which means when exposed to the elements without a protective coating, it will begin to corrode at a much faster rate and will require replacement sooner.

 

Composition
A closer look at the composition of these materials reveals further differences. Mild steel is mainly composed of iron and a small amount of carbon. Corten steel, while also made up of iron and carbon, is an alloy steel. The additional alloying elements include chromium, nickel, copper and phosphorous, providing Corten steel with its unique self-protecting properties and giving it an edge in terms of longevity

 

Cost
Another major difference between Corten and mild steel is their price point. Corten products typically cost around 50% more on average than mild steel products. However, given Corten's longevity and lower maintenance needs, it represents a long-term investment. Mild steel is certainly a cost-effective alternative, but if a protective coating, such as powder coating or galvanising, is applied for added longevity, the cost comparison with Corten starts to level out.

 

Sustainability
In today's environmentally conscious world, it's essential to consider the sustainability factor. Both Corten and mild steel are 100% recyclable, aiding in reducing environmental footprint. Arguably, Corten Steel takes the lead in environmental friendliness. Its unique property of forming a protective layer eliminates the need for paint or a protective coating which can be harmful to the environment.

Gnee Garden is a famous Corten steel manufacturer in China, supplying Corten steel products for architectural and garden applications.if you need it, please contact us!

 

Frequently Asked Questions

Q1. Can mild steel be used outdoors without any protection?
Not for long-term use. Unprotected mild steel will continue to corrode when exposed to moisture and oxygen, eventually losing structural thickness. It requires paint, galvanizing, or another coating for lasting outdoor use.

 

Q2. Is Corten steel always the better choice for outdoor projects? Not always - for budget-constrained structural projects that will remain protected or painted, mild steel can be more cost-effective. Corten is the better choice specifically when you want a low-maintenance, uncoated, naturally weather-resistant finish.

 

Q3. How much more expensive is Corten steel than mild steel?
Corten products typically cost around 50% more than mild steel on average. However, when mild steel needs a protective coating like powder coating or galvanizing for outdoor use, the total cost gap narrows considerably.