How to Weld Corten Steel? Strong and Solid Welds

Marcus Colson Last updated on September 18, 2023
Reading Time: 11 Minute

We often receive questions about the intricacies of welding specific materials. How to weld corten steel is a topic that stands out among them.

Corten steel, known for its weathering properties and distinctive appearance, has specific requirements when it comes to joining pieces.

Why is it different, and what should you know before starting your welding project?

Let’s uncover the essential steps and best practices to ensure a strong and durable weld with corten steel.

What is Corten Steel?

Corten steel has, over time, become a material of choice for many architectural and artistic endeavors. Its rich, rusted finish and longevity give it an edge over other types of steel.

But what really makes corten steel so unique?

Characteristics of Corten Steel

At its core, corten steel is a group of steel alloys designed to avoid the need for painting.

The lack of paint finish allows it to form a stable rust-like appearance after several years of exposure to weather.

Its specific combination of metals gives it not only a signature appearance but also particular durability. The rust layer that forms on its surface protects the inner layers from further corrosion.

Key Components

  • Carbon: Provides hardness and strength
  • Manganese: Boosts its ductility and toughness
  • Silicon: Enhances its resistance against corrosion
  • Copper: Further increases resistance to corrosive elements

Note: This unique blend of elements makes corten steel highly resilient against environmental factors, eliminating the need for additional protective coatings.

Common Uses

From bridges to sculptures, and from facades to planters, corten steel finds its place in various applications.

Architects and artists have leveraged its unique aesthetics, opting for corten in designs that require a rustic yet sophisticated look.

Furthermore, its durability and low maintenance have made it a favorite for outdoor installations and structures.

So, with an understanding of what corten steel is and its exceptional properties, one might wonder how to weld it efficiently.

Let’s delve into the specifics of welding this distinct alloy.

What Type of Welder to Weld Corten Steel?

The selection of the right welding equipment plays a pivotal role in achieving a solid bond with corten steel.

This steel alloy, with its particular composition and properties, requires a specific type of welding technique to ensure that its signature rusted appearance remains intact.

So, what tools should one opt for?

TIG Welding

Tungsten Inert Gas (TIG) welding is often a top choice when dealing with corten steel.

  • Precision: TIG welding offers remarkable control, ensuring a clean weld even on thinner materials.
  • Versatility: Suitable for a variety of metals.
  • Quality: Produces high-quality welds with minimal spatter.

MIG Welding

Metal Inert Gas (MIG) welding is another preferred method for corten steel.

  • Efficiency: MIG welding can be quicker than TIG, making it ideal for larger projects.
  • Simplicity: Easier for beginners to grasp and employ.
  • Adaptability: Works well with a range of metal thicknesses.

Stick Welding

While less commonly used for corten, stick welding or Shielded Metal Arc Welding (SMAW) can be effective in certain situations.

  • Portability: Requires less equipment, making it more portable than TIG or MIG.
  • Affordability: Generally, a cost-effective option for small projects.

Note: Regardless of the method, using the right filler material is paramount. For corten steel, a low alloy filler is ideal.

Factors to Consider

When deciding on the welder type, several considerations come into play:

  1. Thickness of the Metal: Different welding methods are suited for varied metal thicknesses.
  2. Project Size: For extensive projects, efficiency becomes vital.
  3. Skill Level: Some methods might have steeper learning curves than others.
  4. Desired Finish: Ensuring the weld does not interfere with corten’s unique patina.

In essence, while there are multiple tools at one’s disposal, the key is to select the one that aligns with the project’s demands and the welder’s expertise.

Proper equipment selection will ensure a strong, durable bond that upholds the distinctive character of corten steel.

Preparing to Weld Corten Steel

Before embarking on the actual welding process, meticulous preparation is indispensable to achieve seamless results with corten steel.

This distinctive steel, renowned for its weather-resistant capabilities and unique rusted patina, demands keen attention to detail during preparation.

What are the steps and precautions that we need to be aware of?

Cleaning the Surface

First and foremost, it’s vital to ensure the steel’s surface is impeccably clean.

  • Dirt and Debris: Use a wire brush to remove any surface contaminants.
  • Oils and Residues: Wipe down the steel with an industrial solvent or acetone.

Note: A spotless surface ensures better weld penetration and reduces the risk of inclusions or weld defects.

Selecting the Right Filler Material

An integral part of the preparatory phase is choosing the right filler.

For corten steel, a filler that matches the base material’s chemical composition is most effective. Typically, AWS classification A5.28 ER80S-G is an excellent match.

Setting Up the Welder

Depending on the chosen welding method, specific settings will optimize the process.

  • Voltage and Amperage: Adjust these based on the steel’s thickness and the chosen filler material.
  • Gas Flow Rate: Ensure a consistent and suitable rate, particularly if opting for MIG or TIG welding.

Joint Design and Fit-Up

The way the steel pieces fit together is of utmost importance.

For many projects, a simple butt joint will suffice. However, larger, more complex projects might require more intricate joints like lap or T-joints.

  1. Tack Welds: Employ these to hold the pieces together before the final weld.
  2. Gap Management: Maintain a consistent gap between the steel pieces, which can aid in achieving uniform weld beads.

Safety Measures

Safety cannot be overlooked. Corten steel, like other metals, releases fumes when welded.


  • Ventilation: Make sure the welding area is well-ventilated.
  • Safety Gear: Always wear a welding helmet, gloves, and flame-resistant clothing.

Test Weld

Before committing to the final weld, we often recommend performing a test weld on a scrap piece of corten.

This allows for adjustments to the welder settings if needed and ensures the chosen filler material works harmoniously with the base steel.

To underscore the significance of preparation, consider the adage: “Measure twice, cut once.” Similarly, for welding, especially with specialized materials like corten steel, careful and comprehensive preparation paves the way for superior results.

While the welding process itself garners much attention, it’s the preceding steps that often determine the outcome’s quality.

By giving due diligence to each preparatory stage, we set the foundation for a successful and durable weld.

Read Also : How to Weld Cast Steel? The Modern Way to a Strong Bond!

Step-by-Step Guide to Weld Corten Steel

Welding corten steel, a material distinguished by its unique weather resistance and alluring appearance, demands precise techniques and proper methodology.

The rust-like appearance of corten doesn’t merely enhance its appeal but serves as a protective layer against further corrosion. Thus, the approach to welding this steel is slightly different from others.

Here is a detailed guide to help you master the task with finesse.

1. Ensure Proper Preparation

As previously detailed, the importance of meticulous preparation cannot be overstated.

To reiterate:

  • Clean the steel surface from dirt, debris, oils, and residues.
  • Choose the right filler material.
  • Set up your welder with correct settings.

Note: Proper preparation directly influences the end result of your welding effort.

2. Secure the Steel

Place the corten steel pieces on your welding table or work area. Use clamps to firmly hold the pieces together, ensuring they don’t move during the welding process.

3. Begin with Tack Welds

Why is this step vital?

Tack welds act as placeholders, holding the corten steel pieces in their desired position before the final welding.

4. Select the Proper Welding Technique

Depending on the specific project and the thickness of the steel, the welding technique can vary.

  • MIG Welding: This method is preferred for its efficiency, especially for thinner sections of corten.
  • TIG Welding: For intricate designs and where precision is paramount, TIG welding is a solid choice.

Which method seems most suitable for your project?

Evaluate and proceed accordingly.

5. Monitor the Weld Pool

While welding, it’s essential to keep an eye on the weld pool’s size and shape. A consistent weld pool ensures uniformity, which in turn guarantees a durable bond.

6. Control the Welding Speed

How quickly should you move?

A consistent pace is key. Move too fast, and you risk weak welds. Move too slowly, and you might burn through the metal.

7. Employ the Right Electrode

Electrode selection is pivotal.

Generally, a low hydrogen electrode compatible with corten’s chemistry produces the best results. Familiarity with your filler material’s specifications aids in this decision.

Read Also : Electrode Welding: Advice for Choose the Right Electrodes

8. Complete the Weld

Once the desired weld length is achieved, slowly pull away from the weld pool, allowing it to cool and solidify.

Refrain from rushing this step; patience ensures the integrity of the weld.

9. Post-Weld Cleaning

After welding, there might be some slag or spatter. It’s prudent to clean these off.

Using a wire brush, gently scrub the weld to enhance its appearance and ensure it matches the surrounding corten steel in aesthetics.

10. Allow Natural Weathering

The hallmark of corten steel is its protective rusted patina. After welding, expose the steel to natural elements.

Over time, the newly welded area will develop the same rusted appearance, ensuring a seamless blend with the rest of the material.

This guide aims to offer clarity and direction in the multifaceted process of welding corten steel.

Precision, patience, and adherence to these steps will undeniably lead to results that not only stand the test of time but also uphold the inherent beauty of corten steel.

Remember, each welding endeavor presents its unique challenges. Adapt, learn, and continuously hone your skills to excel in this endeavor.

Tips To Weld Corten Steel

Corten steel, known for its distinctive, rusted appearance and durable nature, requires specialized techniques when welding.

The very traits that make corten steel desirable also make the welding process distinct from other types of steel.

Drawing from our extensive experience, we’ve curated a list of essential tips to ensure a smooth welding process for this unique material.

1. Prioritize Surface Cleanliness

Achieving a flawless weld starts with a clean base.

  • Remove all contaminants, rust, and mill scale.
  • Employ a wire brush or grinder, ensuring that the surface gleams, free from any impediments.

2. Use Compatible Filler Materials

Why does filler material matter?

A well-matched filler ensures a sturdy weld that melds seamlessly with the natural traits of corten steel.

Typically, electrodes made of weathering steel or stainless steel are apt choices. Familiarize yourself with filler specifications to make an informed decision.

3. Perfect the Balance of Heat

Welding corten steel necessitates an equilibrium of heat input.

  • Avoid excessive heat, as it can lead to warping or burn-through.
  • Conversely, too little heat can result in weak welds.

4. Practice Bead Placement

Are you aware of bead placement’s significance?

Achieving the right bead profile ensures durability and aesthetic appeal. Aim for consistency in size and shape, which subsequently guarantees a cohesive look.

5. Control Travel Speed

The speed at which you travel while welding plays a pivotal role.

  • A consistent pace ensures even distribution of heat.
  • This uniformity translates to welds that both look impeccable and perform optimally.

6. Shielding Gas Selection

Optimal shielding gas selection can make or break your welding experience.

  • A mixture of argon and carbon dioxide is often recommended.
  • This combination reduces spatter, ensuring a smoother welding process.

Note: Shielding gas not only protects the weld but also impacts its overall quality.

7. Allow for Natural Rusting After Welding

One of corten’s hallmark traits is its rust-like appearance, which serves as a protective layer.

  • After welding, expose the steel to the elements.
  • Over time, this exposure will induce the desired rusted patina on the fresh weld.

8. Proper Storage of Filler Metals

Ensuring the longevity and effectiveness of your filler metals is indispensable.

  • Store them in a dry, cool place.
  • Any moisture can compromise the integrity of the filler, leading to suboptimal welds.

9. Regularly Monitor Equipment

Regular checks on your welding equipment can spell the difference between success and subpar results.

  • Ensure the proper functioning of all components.
  • Replace worn-out parts promptly.

10. Post-Weld Inspection is Key

After completing the welding process, it’s prudent to inspect your work.

  • Check for inconsistencies or imperfections.
  • Address any issues promptly, ensuring the longevity and aesthetics of the weld.

Corten steel, with its array of advantages, is a material that demands respect and understanding.

Each welding endeavor with this material is a unique challenge, necessitating a blend of skill, knowledge, and the right approach.

By adhering to these tips and continually refining your technique, you can master the art of welding corten steel, ensuring results that are both visually captivating and structurally sound.

Remember, the path to mastery is paved with dedication, practice, and a thirst for knowledge.

How will you elevate your welding expertise?

Common Problems to Weld Corten Steel and their Solutions

Corten steel, recognized for its weathering properties and rusted finish, poses some unique challenges during the welding process.

Thankfully, with understanding and expertise, these challenges can be mitigated.

We’ve compiled a list of common problems faced while welding corten steel, along with their effective solutions.

1. Inconsistent Rust Formation

Problem: After welding, you might notice uneven rust formation on the steel surface, leading to an aesthetically unpleasing finish.

Solution: Ensure the welded area is exposed to consistent weather conditions. If certain areas are shielded from rain or moisture, they might not develop the same patina. Strategic placement post-welding can promote uniform rusting.

2. Excessive Spatter

Problem: Welding can sometimes result in excessive spatter, leading to an uneven surface.

Solution: Adjusting the voltage and wire feed speed can help. Moreover, utilizing a gas mixture predominantly consisting of argon can reduce spatter.

Read Also : What is Welding Spatter: Causes and Tips to Avoid It

3. Warping or Distortion

Problem: Due to high heat input, corten steel can warp or distort during the welding process.

Solution: Using a technique that distributes heat evenly, such as stitch welding, can minimize this. Cooling the weld zones gradually, and clamping the workpieces securely can further prevent distortion.

4. Poor Fusion

Problem: Occasionally, the weld might not fuse adequately with the base metal, compromising the joint’s strength.

Solution: This can be rectified by ensuring the welding arc is directed towards the joint’s leading edge and by maintaining a short arc length.

5. Cracking

Problem: Welds sometimes develop cracks, either immediately after welding or after some time.

Solution: Opting for a filler material compatible with corten steel’s composition can avert this issue. Slow cooling the weld also aids in reducing stresses that cause cracking.

Note: Remember to always store your filler materials in a dry environment to ensure their efficacy.

Read Also : Welding Crack: Causes & Effective Prevention Methods

6. Weakened Corrosion Resistance

Problem: The welded area might not display the same corrosion resistance as the rest of the corten steel piece.

Solution: Ensure you’re using filler materials specifically designed for weathering steels. This ensures that the weld area develops a similar protective oxide layer as the base metal.

Tackling the intricacies of welding corten steel might seem daunting initially.

However, with the right knowledge and techniques, achieving a perfect weld is entirely within reach. Armed with these solutions, you’re well-prepared to face common welding challenges head-on.

What other questions or concerns might arise during your welding endeavors?

FAQs on Welding Corten Steel

Why is corten steel favored for outdoor structures?

Corten steel possesses a natural resistance to weathering, allowing it to withstand adverse conditions without corroding. Over time, it develops a protective rust-like appearance, which not only offers protection but also provides aesthetic appeal, making it a preferred choice for outdoor projects.

Can I use any filler material for welding corten steel?

No, it’s crucial to use filler materials specifically designed for weathering steels. These ensure that the welded area develops a protective oxide layer, similar to the base metal, to maintain its corrosion resistance.

How does welding speed impact corten steel?

Welding speed affects heat input. A slow welding speed can lead to excessive heat, increasing the risk of warping or distortion. Conversely, very high speeds might compromise weld penetration and strength. Striking a balanced speed is crucial.

Is pre-heating necessary before welding corten steel?

Pre-heating isn’t always necessary but can be beneficial for thicker sections. It helps in reducing the cooling rate after welding, thus minimizing the risks of cracking and ensuring better fusion.

Can I paint or coat the welds on corten steel?

Yes, you can paint or coat welds. However, to maintain the distinctive appearance of corten steel, it’s essential to choose coatings that match the rust-like patina or let the weld area naturally weather to match the surrounding area.

Does corten steel require a specific welding environment?

While corten steel doesn’t mandate a specific environment, welding in clean conditions free from contaminants like dirt or moisture can lead to better weld quality and reduce potential defects.

How do I clean corten steel before welding?

Cleaning with a wire brush to remove loose rust or scale is recommended. Using a degreaser or acetone can further ensure the surface is free from oil or contaminants, ensuring a cleaner weld.

Are there any safety precautions to take while welding corten steel?

Safety precautions for welding corten steel are akin to other welding operations. Wear protective gear, ensure adequate ventilation, and avoid inhaling fumes. Given corten’s alloying elements, it’s pivotal to ensure proper safety measures.

Does the rust-like patina affect the weld’s strength?

The rust-like patina on corten steel is a protective oxide layer. While it doesn’t contribute directly to the weld’s strength, by preventing further corrosion, it ensures the longevity and integrity of the weld over time.

Can I use traditional welding methods for corten steel?

Yes, traditional welding methods such as MIG, TIG, and stick welding can be employed for corten steel. The key is selecting the right filler materials and ensuring proper technique to achieve strong, corrosion-resistant welds.

Read Also : How to Weld Square Tubing? Effective, Strong, and Perfect


Mastering the process of welding corten steel requires a meticulous understanding of the material and the application of specific techniques.

As we’ve seen, attention to details, from pre-cleaning to selecting the right filler material, plays a critical role in ensuring successful results.

Always prioritize safety and quality to achieve welds that not only look aesthetically pleasing but also stand the test of time.

Remember, expertise comes with practice and continuous learning. So, equip yourself with knowledge and tackle each welding task with confidence.

Was this article helpful?
Yes No
Marcus Colson
Marcus Colson

Welding is more than a hobby for me - it's a passion. The art of fusing metal together to create something new and functional never gets old. From intricate sculptures to sturdy structures, I love the endless possibilities that welding offers.

Leave a Comment