Corten steel is known for being difficult to weld. However, this is only partly true. What is actually difficult, however, is the welding process itself. This is because Corten steel is best welded with electrodes and the surface later must be removed.
If you want to weld Corten steel, you should definitely use Corten B material. This Corten steel does not have a phosphorus alloy and is, therefore, better suited for welding than Corten A. But why is it so difficult to weld Corten steel? The problem with welding corten steel lies in the material type. Also, it is best to use alkaline coated electrodes for Corten steel. Some beginners find it difficult with electrodes because they have to be ignited correctly. In addition, you have to guide the electrode by hand, which is just as difficult for beginners. In this article, you’ll find out more tips for welding corten steel.
Corten steel Trusted Source What is Corten Steel? - Definition from Corrosionpedia This definition explains the meaning of Corten Steel and why it matters. www.corrosionpedia.com is a material recognizable by its rust-like brown-orange color. Widely used in the urban environment (street furniture, architecture), in art, and now more and more in home decor (corten braziers, fences, etc.) it owes its popularity to:
Its rust coloring is a protective layer that forms over time depending on the exposure of the steel to weather factors (rain, sun, wind, etc.).
Its name “COR-TEN” is derived from its two main properties: COR for “corrosion resistance” and TEN for “tensile strength.”
Now that you have a more precise idea of what Corten steel is, we will find out why it rusts, and especially why this rust is a positive process! For this, we must understand its composition.
A little chemistry has never killed anyone, plus it’s time to shine in society when your friends ask you questions!
If we had to translate this formula into more universal jargon here is what we could say. Corten steel is steel composed of an alloy of Nickel Molybdenum, Chromium (Cr), Copper (Cu), as well as Phosphorus (P). These alloys added to steel (Fe) increase the corrosion resistance of iron since they form a self-protective surface layer that is called a patina. This patina becomes poorly permeable to oxygen, thus protecting the steel (Fe).
It takes 1 to 3 years depending on the exposure of Corten steel to atmospheric conditions (alternating dry and wet periods) for the protective layer to mature.
The maturity of the steel is reached when the steel no longer makes any trace or soiling to the touch or in the presence of humidity (orange castings).
Now let’s go into a little more detail. As already mentioned, COR-TEN steel is weatherproof. This property arises from its very low alloy content (less than 1%), in which the main elements are copper and chromium.
Phosphorus is also added to some weatherproof structural steels. Phosphorus increases the weather resistance of the steel, but it does mean that special precautionary measures have to be taken when welding.
The weather resistance of the Corten steel is created by the formation of a rust layer, which at the same time acts as a protective shield against the internal rusting of the steel.
The steel develops this so-called patina under natural weathering with a wet-dry cycle in one to two years. Then the layer is relatively dense and firmly adhering. The development process will be slowed down considerably in the following years. The progress of the rusting process can also be recognized by the color. While the brown color is still relatively light in the first few weeks, it gets darker and darker over time.
With Corten steel, it is important to pay attention to the alternation between moisture and dryness. The protective surface contains fine cracks at one point or another. If the moisture persists for a long time, it penetrates the cracks and falls on the steel underneath. The steel sheet starts to rust from the inside.
Incidentally, the process of rust formation can also be accelerated by using alkalis and acids.
The so-called COR-TEN steel is becoming increasingly popular. Especially in gardening and landscaping, but also inside the house. The rust look of steel has come more and more into focus in recent years. Used as a planter or in raised beds, fire pillars, privacy screens, fences, or garden furniture – the possible uses and designs are very diverse.
COR-TEN steel is a weatherproof structural steel. It is a popular material that is used in building construction, hall construction, road bridge construction, crane construction, container construction, mast construction, chimneys, and steel sculptures since the 1970s.
As it belongs to the group of weatherproof structural steels, it has a decisive advantage over “normal” structural steels: it can mainly be used unprotected, as it has a significantly increased resistance to atmospheric corrosion.
Incidentally, the world’s fifth-longest single-span arch bridge, the New River Gorge truss bridge Trusted Source New River Gorge Bridge (U.S. National Park Service) New River Gorge Bridge www.nps.gov , located in the USA, more precisely in West Virginia, was made of Corten steel. It is the largest bridge made of weatherproof steel.
The fact that COR-TEN steel, like other weatherproof structural steels, is largely corrosion-resistant, is due to a fact that makes its very special appearance: over time it forms so-called noble rust and thus acquires a natural, earthy rust color, which is also what it is what makes it very popular with artists and architects.
The corrosive characteristics of this special steel means a lot has to be considered when welding it. The three most common welding methods – stick welding, MIG welding, and TIG welding – can be used to weld this material.
The welding rules here apply to the welding material. As a welding filler, there are mainly electrodes, basic stick electrodes to be precise. These electrodes must be welded in the positive pole. Normal electrodes for structural steel, for example, are mostly rutile cellulose stick electrodes that are welded to the negative pole.
It should also be noted that basic stick electrodes or stick electrodes with a basic coating are significantly more difficult to weld. What starts with the ignition properties, continues with the general welding properties, and ends with the fact that the electrode can only be re-ignited when the core rod is slightly freed from the cover.
But that does not mean that it is not possible. It just takes a little more practice and skill. Especially when processing fine-grain structural steel. Many still work with basic stick electrodes today and an extremely high level of quality is achieved in the process. So welding Corten steel with stick electrodes is quite possible and by no means impossible.
To be able to weld Corten steel at all, you must first remove the patina. So you grind the steel in the immediate welding area until it is bright.
Especially if you have never or only rarely welded with electrodes, this intermediate step is worthwhile (and otherwise also with an unknown material). Take a test piece and just try out how the electrode behaves in connection with the Corten steel. In this way, you will also find the optimal welding position for yourself and know immediately whether you need to fix the workpiece a little higher or lower without risking spoiling the final piece.
Now it’s time to weld. Of course, you have to cut the parts to the correct size and lay them out. Make sure you wear long clothing and tight shoes when welding. It is very uncomfortable when a red-hot piece of steel falls on your foot and burns through your sock.
You shouldn’t forget your welding helmet either. Welding protection for the eyes that you have to hold on to with one hand is unsuitable when welding with electrodes because you need both hands.
Ignite the electrode exactly at the weld seam. If you have to stop and ignite the electrode again, first remove the basic coating with a hammer.
TIG welders are also suitable for welding weathering steel like Corten steel. However, the electrode also matters here. Using the wrong filling metal will decrease the yield and tensile strength of the metal. It will also reduce the anti-corroding properties of the metal.
Tungsten electrodes are used with filler wire when TIG-welding Corten. The most popular welding rods for this type of steel are the E70XX and the E60XX line.
The best electrode will be that with a point as you have to focus the heat specifically around the welding seam. The electrode diameter must be around half of what the metal measures in thickness. The welding machine must also be set to straight polarity under direct current.
There are also MIG welders and consumables for Corten steel. Mild MIG wires such as the PGN – ER70S-6 must be used. But the consumables are relatively expensive. It is therefore rather unsuitable, especially for smaller applications. Since only 5kg or 15 kg rolls are offered and a price of at least 20-25 per kg is required.
The best types of filler rods are basic low hydrogen electrodes depositing steel containing copper, nickel, and chromium. The filler rods must be designed for welding all steels resistant to atmospheric corrosion (marine, industrial, rural).
Also, it is best to use alkaline coated electrodes for Corten steel. Some beginners find it difficult with electrodes because they have to be ignited correctly. In addition, you have to guide the electrode by hand, which is just as difficult for beginners.
When TIG welding, it’s important to use tungsten electrodes with filler wire. The most popular welding rods for this type of steel are rods of the E70XX and the E60XX line such as the WeldingCity 5-Lb Stick Welding Electrode Rods. This set contains E7018 rods that are made from carbon steel. As for the welding machine, flux cored welders, stick and TIG welders are ideal.
Corten steel is a weathering steel, which is composed of copper, chromium, nickel, and phosphorus. It is a type of steel made with a chemical composition that causes oxidation. These particular characteristics protect the piece made with this material against atmospheric corrosion without practically losing its mechanical characteristics.
However, welding Corten steel can be difficult especially when working on the wrong Corten steel, which is Type A. Type B is easier to weld.
To be able to weld Corten steel at all, you have to first remove the patina. So you have to grind the steel in the immediate welding area until it is bright. This process is required especially for beginning welders.
In addition, there are filler rods that are more suitable for welding Corten. By following our advice, you should have no problem welding Corten.
