Corten steel welding, plasma cutting and machining.
In this article there are hints and instructions for corten steel welding. In addition, there are general instructions for processing, machining and plasma cutting of corten steel.
Corten steel is a weather-resistant structural steel that is becoming increasingly popular due to its appearance. The surface forms a very dense and, when used correctly, homogeneous rusting surface. Especially for many metalworkers, welders etc. it is a big change, for years corrosion was the enemy and suddenly rust is the trend. But this is a completely different subject… and certainly partly only my personal opinion.
At the end of the article there is a video for you about corten steel.
What is corten steel
Ok what is corten steel and what special properties does it have?
Corten steel is a weather-resistant structural steel that has two properties that make it so popular.
- Firstly, it forms a very even and visually attractive rust layer. Secondly, a barrier layer of sulphates or phosphates is formed under this rust layer to prevent the material from further rusting. Rusting through as with normal steel is therefore not possible.
This results in many possible applications, especially in decorative outdoor use; even fountains or waterfalls are made of this material. Corten steel therefore requires neither paint nor other corrosion protection.
But there are some contemporaries who have coated the finished corrosion layer with a clear varnish. Which then has optical reasons and rather does not serve as additional corrosion protection.
A basic distinction is made between A & B grade corten steel. Normally, however, only Corten steel B is of importance to us, as it is easy to weld and process.
Corten steel welding
What should be observed when welding corten steel? Addendum, welding procedure, special features.
Corten steel B has welding properties that are ok, but unfortunately not more. Which means that Corten steel can be welded, but not as well as mild steel or stainless steel. It is important to use a special additive for corten steel. Often normal welding consumables are offered for mild steel, which is fundamentally wrong. So what is the problem? Filler metal must be of the same type to ensure the same properties such as strength and corrosion resistance. Corrosion resistance in particular is a general problem. Normal welding filler for structural steel, for example, rusts without corrosion protection, whereas Corten steel forms a barrier layer under a reaction layer. SG2 welding filler for corten steel would therefore rust through, while the base material would only form a rust layer on the surface. As a side effect, the area of the weld seam would also rust differently (colour, structure, appearance).
Welding corten steel with electrodes
The main welding consumables available are electrodes, basic stick electrodes to be precise. The important thing is to weld these electrodes at the positive pole. Normal electrodes for mild steel, for example, are mostly rutile cellulose electrodes that are welded at the negative pole.
It should also be noted that basic rod electrodes or rod electrodes with a basic coating are much 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 if the core rod is slightly freed from the coating. But this is not to say that it is not possible. It only needs a little more practice and skill. Especially when processing fine-grained structural steel, for example, we still often work with basic rod electrodes and achieve an extremely high quality level.
So the welding of corten steel with stick electrodes is absolutely possible and by no means impossible.
Corten steel with MAG welding
There are also some MAG additives for corten steel. But they are relatively expensive and can only be welded halfway well. Especially for smaller applications they are not suitable. Since only 5kg or 15kg rolls are offered and a price of 20-25 per kg is required as a minimum.
Corten steel welding with WIG and in case of emergency
In case of an emergency or if the backside is not visible, for example, a bracket or similar can be welded on with normal additions for carbon steel / mild steel. Of course, a protective layer must be applied with paint or zinc spray. The whole thing withstands normal loads. I have also used it successfully several times as described.
In the same way I consider it completely unproblematic to tack components with TIG and to use SG2 as welding filler. During the subsequent complete welding process, the tacking point is then only slightly sanded and then welded over. Then of course special additive is used again. So prepare it perfectly with TIG and weld it later with the right electrode.
Corten steel plasma cutting
My plasma cutter which perfectly cuts corten steel, read more here.
As can also be seen in the video, Corten steel can be cut perfectly with a plasma cutter. Not only straight cuts but also any shape is possible with a plasma cutter. For example letters, figures, curves, long holes etc. are possible. This means that there is no limit to creativity when processing Corten steel, or the limit is only in the head of the user. In my test I cut / burned 2mm, 4mm and 6mm and could not find any differences to normal construction steel. Of course it would be possible to cut corten steel with acetylene / oxygen oxyfuel. But who has this possibility and plasma cutting is much more the state of the art.
Corten steel processing & machining
Corten steel can otherwise be processed just as well as mild steel. Whether drilling, chamfering or rounding, everything is possible with Corten steel. Only the welding is a little more difficult. But with a little practice, even that is no longer a problem.
Corten steel the perfect rust layer / make Corten steel rust faster
For the perfect rust layer the corten steel needs some help.
Firstly, the normal delivery condition is provided with a so-called rolling skin, which forms an initial protective layer against corrosion. This layer must be removed by chemical means or fine grinding. The result must be as uniform as possible. This is the only way to achieve an even rust layer.
The layer of rust on corten steel can now form due to natural environmental influences, but this can quickly take a few weeks or months. It will not work indoors without help. Or it is helped by so-called rapid rusting. In this way a great effect can be achieved after a short time.
It is recommended to apply the remedy with a roller and to repeat the whole procedure regularly. This gives the popular rust effect.