What is the difference between Corten A and B?
Corten steel, also known as weathering steel, is a type of steel used often in outdoor construction. It was created to avoid the need for painting when exposed to the weather. Corten A and Corten B develop a rusted look within a few months, much faster than regular steel.Â
This article explains the features of Corten steel and the differences between the Corten A and B Steel grades.
What is Weathering Steel?
The main benefit of Corten A and Corten B weathering steel is their ability to resist rust. Unlike most low alloy steels, this type of steel doesn’t rust when it gets wet.
Instead, Corten A and Corten B weathering steel develop a stable layer of rust known as a ‘patina.’ This layer acts as a protective barrier against further corrosion. Unlike standard steel, where rust can spread and cause damage, the patina on Corten steel helps keep the steel underneath strong and protected.
Key Features of Corten (or Cor-ten) Steel
All grades of Corten steel are weather-resistant and made with a copper-chromium alloy. They are very good at withstanding the effects of the weather, especially compared to regular unalloyed steel. Both Corten A weathering steel and Corten B look attractive and are used in various architectural projects like sculptures and bridges.
Corten A weathering steel contains extra phosphorus, making it ideal for decorative facades and gas flue applications. On the other hand, Corten B is more suitable for heavy-duty and load-bearing structures.
Corten A Weathering Steel
Corten A is formulated with alloying elements such as copper, nickel, and chromium, along with phosphorus. This composition makes Corten A suitable for gas flue applications and commonly used for aesthetic fascias. However, it’s not recommended for heavy load-bearing applications.
Corten B Weathering Steel
Similar in composition to Corten A, Corten B is highly corrosion-resistant and widely utilized in structures. Its strength makes it more suitable for load-bearing applications compared to Corten A, making it a preferred choice for projects requiring structural integrity.
Difference Between Corten A Chemical Composition and Corten B Chemical Composition
| Grade | C | Si | Mn | P | S | Al | V | Cu | Cr | Ni |
|---|---|---|---|---|---|---|---|---|---|---|
| Corten A | 0.12 | 0.25/0.75 | 0.20/0.50 | 0.07/0.15 | 0.030 | 0.015/0.06 | – | 0.25/0.55 | 0.50/1.25 | 0.65 |
| Grade | C | Si | Mn | P | S | Al | V | Cu | Cr | Ni |
| Corten B | 0.19 | 0.30/0.65 | 0.80/1.25 | 0.035 | 0.030 | 0.020/0.06 | 0.02/0.10 | 0.25/0.40 | 0.40/0.65 | 0.40 |
Difference Between Corten a Mechanical Properties and Corten B Mechanical Properties
| Grade | Thickness (mm) Strip Products |
Plate Products | Yield Strength Rel N/mm² Minimum |
Tensile Strength Rm N/mm² Minimum |
Elongation A50 % Minimum |
|---|---|---|---|---|---|
| Corten A | 2 – 12 | 6 – 12 | 345 | 485 | 20 |
| Grade | Thickness (mm) Strip Products |
Plate Products | Yield Strength Rel N/mm² Minimum |
Tensile Strength Rm N/mm² Minimum |
Elongation A50 % Minimum |
| Corten B | 2 – 13 | 6 – 40 | 345 | 485 | 19 |
Corten A Grades and Equivalents
| Corten | EN 10025-5:2004 |
|---|---|
| Corten A | S355 J0WP |
Corten B Grades and Equivalents
| Corten | EN 10025-5:2004 |
|---|---|
| Corten B | S355J2W |
Uses of Corten A vs Corten B
Corten steel, including Corten A and Corten B weathering steel, is known for its weather-resistant properties and attractive appearance. Although both types are durable and visually appealing, they are designed for different uses.
Corten A steel is made with copper, chromium, nickel, and phosphorus. It is often used for outdoor sculptures, bridges, and building facades. The rust-like surface it forms protects it from further corrosion, making it ideal for architectural and artistic projects that are exposed to the weather.
Corten B steel has extra alloys like vanadium, copper, and manganese, which enhance its resistance to corrosion. This makes it a good choice for marine environments, such as shipping containers and boat hulls, where it needs to withstand harsh conditions.
Advantages of Corten A and Corten B
| Advantage | Corten A Steel | Corten B Steel |
|---|---|---|
| Natural Corrosion Protection | Forms a stable rust-like surface that protects against further rusting, eliminating the need for painting and regular maintenance. | Forms a stable rust-like surface that protects against further rusting, eliminating the need for painting and regular maintenance. |
Corrosion Resistance | Good corrosion resistance in general weather conditions. | Higher corrosion resistance, especially in salty or acidic environments, suitable for marine applications. |
Enhanced Strength and Durability | Suitable for general applications with adequate strength and durability. | Contains additional alloys (vanadium, copper, manganese) that enhance strength and durability, ideal for heavy-duty applications like bridges. |
Aesthetic Appeal | Unique rust-like appearance adds to its aesthetic value, popular for artistic installations and outdoor sculptures. | Unique rust-like appearance adds to its aesthetic value, popular for artistic installations and outdoor sculptures. |
Disadvantages of Corten A and Corten B
Disadvantage | Corten A Steel | Corten B Steel |
|---|---|---|
Initial Cost | Generally more expensive than traditional carbon steel due to its unique properties and alloys. This cost may be offset by lower maintenance and painting needs over time. | Generally more expensive than traditional carbon steel due to its additional alloys. This cost may be offset by lower maintenance and painting needs over time. |
Staining or Runoff | Can cause staining or runoff during weathering, which may damage surrounding materials or structures. | Can cause staining or runoff during weathering, which may damage surrounding materials or structures. |
Aesthetic Preferences | The rust-like appearance might not fit all design styles or preferences, especially if a uniform or traditional look is desired. | The rust-like appearance might not fit all design styles or preferences, especially if a uniform or traditional look is desired. |
Application Suitability | May not be suitable for all applications. Environmental conditions, load-bearing needs, and aesthetic requirements should be considered. | May not be suitable for all applications. Environmental conditions, load-bearing needs, and aesthetic requirements should be considered. |
