Rust in steel

Not every steel is stainless. Since steel is one of the ferrous metals, depending on the alloy, rust is also common in steel. In addition, one must also take into account special types of corrosion that can occur in steel. How rust behaves on different steels, you can read here.

Types of steel

Steel can be divided into different groups:

  • ground steels
  • quality steels
  • Micro-alloyed steels
  • Low alloy steels
  • stainless steels
  • High-alloy stainless steels

This classification is only a rough guideline. In total, about 2,500 different types of steel are registered in the European register. The carbon content is an important factor for the properties of unalloyed steel.

Corrosion behavior of steel

Each type of steel has a different corrosion behavior. High-alloyed stainless steels are generally more resistant to corrosion than low-alloyed or unalloyed steels (mass and quality steels).

However, this too is only a rough guide: due to the many technical alloys, the corrosion behavior within a steel group can also be very different. For example, stainless steels with a very high chromium content are in turn more susceptible to corrosion.

Most unalloyed steel grades are almost as susceptible to corrosion as iron if they are not specifically treated with rust inhibitors.

Problem contact corrosion

Contact corrosion also plays a major role in stainless steels. Especially in the construction sector, therefore, the use of different types of steel side by side is avoided as much as possible to avoid problems caused by contact corrosion.

CorTen steel

This is a special type of steel, which is also used as structural steel. Due to the weather, this steel forms a thick, stable layer of rust, under which there is a very dense barrier layer of sulphates and phosphates.

This barrier layer reliably prevents further corrosion. The exterior of CorTen steel looks evenly rusted, but inside the steel remains stable for a long time due to the effect of the barrier layer.

It is therefore often used for bridge constructions that are safe from corrosion even without regular protective coating. In the visible area of ​​buildings, elements of CorTen steel, which are supposed to give an individual look, are sometimes found as a design element.

Tips & Tricks

Always pay attention to what influences steel is exposed to / weather, etc.) and protect it accordingly against rust. Not all grades of steel are equally suitable for all applications, so take care when choosing them.

Video Board: How to Rust Metal in Minutes!